[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fST2u_BoHK53BCC0Nyc4HFEwtV7nC7hdEI1DJisTSMRE":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":142,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":207},[4,8,12,16,20,24,28,32],{"title":5,"slug":6,"path":7},"About Microbeonline.com","about-microbeonline-com","\u002Fabout-microbeonline-com\u002F",{"title":9,"slug":10,"path":11},"About Me","about-me","\u002Fabout-microbeonline-com\u002Fabout-me\u002F",{"title":13,"slug":14,"path":15},"Advertise with Us","advertise-us","\u002Fadvertise-us\u002F",{"title":17,"slug":18,"path":19},"Privacy Policy","privacy-policy","\u002Fprivacy-policy\u002F",{"title":21,"slug":22,"path":23},"Authors","authors","\u002Fauthors\u002F",{"title":25,"slug":26,"path":27},"Microbes","microbes","\u002Fmicrobes\u002F",{"title":29,"slug":30,"path":31},"Books","recommended-books","\u002Frecommended-books\u002F",{"title":33,"slug":34,"path":35},"Tags","tags","\u002Ftags\u002F",{"type":37,"data":38},"blog",{"slug":39,"title":40,"description":41,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":44,"lastUpdatedDate":45,"draft":46,"category":47,"image":42,"body":48,"faq":49,"commentsClosed":46,"tags":74,"related":75,"comments":138},"dna-replication","DNA Replication: Steps, Mechanism, and Diagram (Prokaryotic)","\u003Cp>DNA replication copies one DNA molecule into two before a cell divides. Learn the semi-conservative mechanism, the step-by-step process at the replication fork, and how leading and lagging strands are built.\u003C\u002Fp>",null,"Acharya Tankeshwar","2022-07-06","2026-08-15",false,"molecular-biology","Every time a cell divides, it must first make a complete copy of its DNA, so that each daughter cell receives the full set of instructions. A human cell copies about 3 billion base pairs, and it does so with remarkably few mistakes. **This copying is called DNA replication,** and it is one of the most important processes in all of biology. It is the reason a single fertilized egg can become a whole organism in which every cell carries the same genetic information, and it is the reason parents pass traits to their children.\n\nThe central question replication has to answer is simple to ask and hard to solve: how do you copy a molecule and be sure the copy is correct? The answer, worked out by experiment, is that **DNA copies itself in a semi-conservative way**. Each of the two old strands is kept and used as a pattern for a new strand. This article explains what that means, why it matters, and how a team of proteins carries it out step by step.\n\n## Why a cell must copy its DNA\n\nDNA carries the instructions a cell needs to build proteins and to function. Before a cell divides into two, it must give each new cell a complete and correct copy of these instructions. If the copy were incomplete or full of errors, the new cell could malfunction or die. So replication is not just copying; it is copying with very high accuracy. This is true in every living organism, from bacteria to humans, which is why replication is a foundation topic across all of biology and health science.\n\n### The three proposed models of replication\n\nWhen scientists first asked how DNA copies itself, three models were possible.\n\nIn the **semi-conservative** model, the two strands of the parent DNA separate, and each old strand serves as a template for building one new strand. Each daughter molecule therefore contains one old strand and one new strand.\n\nIn the **conservative** model, the parent molecule would stay fully intact, and an entirely new double-stranded copy would be made separately. The daughter would be made of two brand-new strands.\n\nIn the **dispersive** model, the parent DNA would be broken into pieces, copied, and reassembled, so that each strand of each daughter molecule would be a mixture of old and new segments.\n\nThe **semi-conservative model is the correct one.** This was shown by the classic Meselson and Stahl experiment, which followed heavy and light nitrogen through successive generations of DNA and found exactly the pattern the semi-conservative model predicts: after one round of replication, every molecule was a hybrid of one old and one new strand. Understanding that replication is semi-conservative is the single most important idea on this page, because everything that follows depends on each old strand acting as a template.\n\n![Replication of DNA - Semiconservative model of replication, Source: BROCK Biology of Microorganism](\u002Fblogs\u002Fsemi-conservative.png)Figure: Semiconservative model of replication, Source: BROCK Biology of Microorganism\n\n### How a template works\n\nA template is a single strand of DNA whose base sequence decides the sequence of the new strand. The rule is base pairing: adenine pairs with thymine, and guanine pairs with cytosine. So if the template reads A, the new strand gets T opposite it; if the template reads G, the new strand gets C. Because both old strands are used as templates, and because base pairing is exact, the two daughter molecules end up identical to the original. This is how copying and accuracy are achieved at the same time.\n\n### The direction problem: why the two new strands are not built the same way\n\nThere is one complication that shapes the whole process, and it is worth understanding before the steps. The two strands of DNA run in opposite directions (they are antiparallel). The enzyme that builds new DNA can add building blocks in only one direction, always adding to the 3′ end so that the new strand grows 5′ to 3′. Because the two templates point in opposite directions, only one new strand can be built smoothly and continuously toward the opening point. The other has to be built in short pieces, in the opposite direction. This single fact explains the leading strand, the lagging strand, and the Okazaki fragments described below. Keep it in mind and the rest follows logically.\n\n## Steps of DNA replication in prokaryotes\n\nReplication is usually described in three stages: initiation, elongation, and termination. The description below uses the bacterium *Escherichia coli*, the best-studied example. The enzymes are named here as the actors in each step; the full mechanism of each enzyme is covered in detail in the companion article on the [enzymes involved in DNA replication](https:\u002F\u002Fmicrobeonline.com\u002Fenzymes-involved-in-dna-replication\u002F).\n\n![DNA replication in prokaryotes - DNA replication in prokaryotes](\u002Fblogs\u002FUntitled-18.png)Figure: DNA replication in prokaryotes\n\n### **Initiation**\n\nReplication does not start just anywhere. It begins at a specific site called the origin of replication. In *E. coli* this origin is named oriC and is about 245 base pairs long. It contains a cluster of short repeated sequences: a set of 9-mer repeats that act as binding sites for the initiator protein, and next to them a stretch of three AT-rich 13-mer repeats. AT-rich DNA is easier to pull apart because A-T pairs are held by only two hydrogen bonds, while G-C pairs have three. The initiator protein binds the 9-mer sites and then opens up the AT-rich 13-mer region, creating a small opened area called the replication bubble.\n\nOnce the DNA is opened, helicase is loaded onto the strands and begins unwinding the double helix, moving in both directions and creating two Y-shaped replication forks that travel away from the origin. As the strands separate, single-stranded binding proteins coat them to keep them apart and protect them, and topoisomerase relieves the twisting strain that builds up ahead of each fork. Each of these jobs is done by a specific enzyme, described on the [enzymes page](https:\u002F\u002Fmicrobeonline.com\u002Fenzymes-involved-in-dna-replication\u002F).\n\n### **Elongation**\n\nNew DNA cannot be started from nothing. Synthesis must begin from a short primer, a small piece of RNA laid down on the template by the enzyme primase. Once a primer is in place, DNA polymerase III extends it, reading the template and adding matching DNA nucleotides to build the new strand in the 5′ to 3′ direction.\n\nBecause of the direction problem described earlier, the two new strands are built differently.\n\nThe **leading strand** is built continuously. Its template allows DNA polymerase to follow the fork as it opens, so one primer is enough and synthesis runs smoothly in one long piece.\n\nThe **lagging strand** is built discontinuously, in short pieces called **Okazaki fragments**. Here the template runs the opposite way, so the polymerase can only work in short stretches away from the fork. Each Okazaki fragment needs its own new primer. Afterward, the RNA primers are removed and replaced with DNA by DNA polymerase I, and DNA ligase seals the gaps between fragments into one continuous strand. This is why the lagging strand needs more steps and more enzymes than the leading strand to copy the same length of DNA.\n\nAccuracy is built into this stage. DNA polymerase III checks each base it adds and can remove a wrong one before moving on. This proofreading is a major reason replication makes so few errors.\n\n### **Termination**\n\nIn the circular *E. coli* chromosome, the two forks travel in opposite directions around the circle and eventually meet on the far side, in a region containing specific termination (Ter) sequences. A protein called Tus binds these Ter sites and acts like a one-way trap: a fork can enter but cannot pass through, so replication stops there. After the two new circular chromosomes are finished, they are often linked together like two rings of a chain, and a topoisomerase separates them so that each daughter cell receives one complete chromosome during cell division.\n\n## Prokaryotic versus eukaryotic replication\n\nThe basic mechanism, semi-conservative copying built on templates and primers, is the same in all organisms. The main differences are in scale and setting.\n\n| Feature | Prokaryotes (e.g. *E. coli*) | Eukaryotes |\n| --- | --- | --- |\n| Location | Cytoplasm (no nucleus) | Nucleus (and mitochondria) |\n| Chromosome shape | Usually one circular chromosome | Several linear chromosomes |\n| Origins of replication | One per chromosome | Many per chromosome |\n| Replication forks | Two, from the single origin | Many, from many origins |\n| Okazaki fragment length | Longer (about 1,000 to 2,000 nucleotides) | Shorter (about 100 to 200 nucleotides) |\n| Main synthesis enzyme | DNA polymerase III | DNA polymerase δ and ε |\n| DNA packaging | Not wrapped around histones | Wrapped around histones |\n| Speed | Fast; a few thousand bases per second | Slower per fork, but many forks at once |\n\nEukaryotes use many origins because their chromosomes are far longer. Copying a human chromosome from a single origin would take far too long, so replication starts at many points at once and the sections are later joined.\n\n*(The enzyme names differ between the two groups and do not match one-to-one. Bacterial DNA polymerase III is the main replicase, while in eukaryotes that role is split. The details are on the [enzymes page](https:\u002F\u002Fmicrobeonline.com\u002Fenzymes-involved-in-dna-replication\u002F); do not try to pair them by number.)*\n\n## Why DNA replication matters\n\nReplication is more than a textbook process. It is the point at which genetic information is passed on, and it connects to several things a health-science student will meet again.\n\nAccuracy and mutation: replication is highly accurate, but not perfect. The rare uncorrected error is one source of mutation, which underlies both evolution and disease.\n\nSpeed and infection: bacteria such as *E. coli* can copy their entire genome quickly, which is part of why bacterial infections can grow so fast.\n\nDrug targets: because replication is essential, several enzymes that carry it out are targets for drugs. The bacterial enzyme DNA gyrase, for example, is blocked by the fluoroquinolone antibiotics. Some anticancer drugs work by interfering with DNA replication in rapidly dividing cells. These connections are developed further on the [enzymes page](https:\u002F\u002Fmicrobeonline.com\u002Fenzymes-involved-in-dna-replication\u002F).\n\n## How to Remember\n\n**Semi-conservative in three words: \"keep one, copy one.\"** Each daughter molecule keeps one old strand and copies one new strand. If you remember only one thing about replication, remember this, because every step exists to serve it.\n\n**Why AT opens first.** The origin is AT-rich because A-T pairs have only two hydrogen bonds, while G-C pairs have three. Fewer bonds means easier to pull apart. Think \"AT = two bonds = the easy zipper,\" which is why the machinery opens the DNA there.\n\n**Leading versus lagging, using your hands.** DNA is only built 5′ to 3′. Point the fingers of both hands toward an opening point in the middle: one hand points \"with\" the opening (leading, one smooth piece), the other points \"against\" it (lagging, built backward in short Okazaki fragments). The direction problem is the whole reason one strand is broken into pieces.\n\n**Okazaki = lagging.** The name to attach to the short pieces is Okazaki, and they are only on the lagging strand. A quick self-check: \"Which strand is discontinuous?\" If your answer names Okazaki fragments, you have the right one.\n\n## Key exam facts in one table\n\n| Fact | Detail |\n| --- | --- |\n| What replication does | Copies one DNA molecule into two before cell division |\n| Mechanism | Semi-conservative (each daughter = one old + one new strand) |\n| Proven by | Meselson and Stahl experiment |\n| Base pairing rule | A with T, G with C |\n| Direction of synthesis | 5′ to 3′ only (adds to the 3′ end) |\n| Start site | Origin of replication (oriC in *E. coli*, \\~245 bp) |\n| Primer | Short RNA piece; needed to start synthesis |\n| Leading strand | Continuous, one primer |\n| Lagging strand | Discontinuous, built in Okazaki fragments, one primer each |\n| Termination (*E. coli*) | Forks meet at Ter sites; Tus protein traps the fork |\n| Prokaryotic origins | One per chromosome |\n| Eukaryotic origins | Many per chromosome |\n\n## Where Students Get Confused\n\n**Semi-conservative does not mean half of each strand is new.** It means each double-stranded daughter molecule has one whole old strand and one whole new strand. The \"half\" is per double helix, not per single strand. Mixing this up is the most common replication error on exams.\n\n**The primer is RNA, not DNA.** Synthesis cannot start on bare template. A short RNA primer is laid down first, and it is later removed and replaced with DNA. Students often assume DNA polymerase starts from nothing; it cannot.\n\n**Leading and lagging are not two different molecules.** They are the two new strands being made at the same fork, at the same time. One is continuous and one is in pieces because of the antiparallel direction rule, not because they are separate events.\n\n**Replication is not transcription.** Replication copies DNA into DNA to prepare for cell division. Transcription copies DNA into RNA to make a working message for protein synthesis. Different purpose, different product. If the product is a full second copy of the DNA, it is replication.\n\n**Okazaki fragments are only on the lagging strand.** The leading strand is one continuous piece. Only the lagging strand is built in fragments.\n\n**References**\n\n1. Madigan MT, Bender KS, Buckley DH, Sattley WM, Stahl DA. *Brock Biology of Microorganisms*. 16th ed. Pearson; 2021.\n2. Watson JD, Baker TA, Bell SP, Gann A, Levine M, Losick R. *Molecular Biology of the Gene*. 7th ed. Pearson; 2013.\n3. Nelson DL, Cox MM. *Lehninger Principles of Biochemistry*. 8th ed. W.H. Freeman; 2021.",[50,53,56,59,62,65,68,71],{"question":51,"answer":52},"\u003Cp>What is DNA replication in simple terms?\u003C\u002Fp>","\u003Cp>DNA replication is the process by which a cell copies its DNA, turning one double-stranded molecule into two identical ones. It happens before a cell divides, so that each new cell gets a complete copy of the genetic instructions.\u003C\u002Fp>",{"question":54,"answer":55},"\u003Cp>Why is DNA replication called semi-conservative?\u003C\u002Fp>","\u003Cp>Because each new double helix keeps one strand from the original DNA and pairs it with one newly made strand. Half of each daughter molecule is old and half is new, which is what \"semi-conservative\" means. This was proven by the Meselson and Stahl experiment.\u003C\u002Fp>",{"question":57,"answer":58},"\u003Cp>What is the difference between the leading and lagging strands?\u003C\u002Fp>","\u003Cp>The leading strand is built continuously in one long piece as the DNA opens. The lagging strand is built in short pieces called Okazaki fragments, because its template runs in the opposite direction and DNA can only be built in the 5′ to 3′ direction. The lagging strand therefore needs more primers and more steps.\u003C\u002Fp>",{"question":60,"answer":61},"\u003Cp>What are Okazaki fragments?\u003C\u002Fp>","\u003Cp>They are the short pieces of new DNA made on the lagging strand. Each one is started with its own RNA primer, then the primers are removed and the fragments are joined into a continuous strand by DNA ligase.\u003C\u002Fp>",{"question":63,"answer":64},"\u003Cp>Why does DNA replication need a primer?\u003C\u002Fp>","\u003Cp>The enzyme that builds new DNA cannot start a strand from nothing. It can only add to an existing 3′ end. A short RNA primer provides that starting point, and it is later replaced with DNA.\u003C\u002Fp>",{"question":66,"answer":67},"\u003Cp>Where does DNA replication take place?\u003C\u002Fp>","\u003Cp>In prokaryotes such as bacteria, it happens in the cytoplasm, since they have no nucleus. In eukaryotes, it happens in the nucleus, and also in the mitochondria for the small amount of DNA found there.\u003C\u002Fp>",{"question":69,"answer":70},"\u003Cp>How is DNA replication different from transcription?\u003C\u002Fp>","\u003Cp>Replication copies DNA into DNA to prepare for cell division, producing a second full copy of the genome. Transcription copies a gene from DNA into RNA to carry instructions for making a protein. The product tells them apart: a full DNA copy means replication, an RNA message means transcription.\u003C\u002Fp>",{"question":72,"answer":73},"\u003Cp>Is DNA replication the same in prokaryotes and eukaryotes?\u003C\u002Fp>","\u003Cp>The core mechanism is the same: semi-conservative copying using templates, primers, and 5′ to 3′ synthesis. The main differences are that eukaryotes use many origins of replication on long linear chromosomes, while bacteria usually use a single origin on one circular chromosome.\u003C\u002Fp>",[39],[76,107],{"slug":77,"title":78,"description":79,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":80,"lastUpdatedDate":45,"draft":46,"category":47,"image":42,"faq":81,"tags":106},"enzymes-involved-in-dna-replication","Enzymes Involved in DNA Replication: Roles at the Fork, with Diagram","The enzymes of DNA replication (helicase, gyrase, primase, DNA polymerase I and III, ligase) explained by their job at the replication fork, with a labeled diagram and the antibiotic that targets DNA gyrase.","2022-09-29",[82,85,88,91,94,97,100,103],{"question":83,"answer":84},"\u003Cp>What are the main enzymes involved in DNA replication?\u003C\u002Fp>","\u003Cp>Helicase unwinds the double helix, gyrase (a topoisomerase) relieves the strain ahead of the fork, primase makes RNA primers, DNA polymerase III carries out the main synthesis, DNA polymerase I removes the primers and fills the gaps, and DNA ligase seals the pieces together.\u003C\u002Fp>",{"question":86,"answer":87},"\u003Cp>What is the difference between DNA polymerase I and III in bacteria?\u003C\u002Fp>","\u003Cp>DNA polymerase III is the main enzyme that builds most of the new DNA strand and proofreads as it goes. DNA polymerase I is the cleanup enzyme: it removes the RNA primers and fills those gaps with DNA.\u003C\u002Fp>",{"question":89,"answer":90},"\u003Cp>Why is the lagging strand made in fragments?\u003C\u002Fp>","\u003Cp>DNA polymerase can only build in the 5′ to 3′ direction. Because the two template strands run in opposite directions, the polymerase cannot follow the fork continuously on the lagging strand. It works in short pieces called Okazaki fragments, each needing its own primer.\u003C\u002Fp>",{"question":92,"answer":93},"\u003Cp>What does DNA gyrase do, and why does it matter clinically?\u003C\u002Fp>","\u003Cp>DNA gyrase is a bacterial type II topoisomerase that removes the positive supercoils building up ahead of the replication fork. It is the target of fluoroquinolone antibiotics such as ciprofloxacin. Blocking gyrase stops replication.\u003C\u002Fp>",{"question":95,"answer":96},"\u003Cp>Is the primer made of DNA or RNA?\u003C\u002Fp>","\u003Cp>The primer is a short piece of RNA, made by primase. It is later removed by DNA polymerase I and replaced with DNA.\u003C\u002Fp>",{"question":98,"answer":99},"\u003Cp>What is the difference between the two exonuclease activities of DNA polymerase I?\u003C\u002Fp>","\u003Cp>The 3′ to 5′ exonuclease activity proofreads by removing a wrong nucleotide just added. The 5′ to 3′ exonuclease activity removes the RNA primer from ahead of the growing strand.\u003C\u002Fp>",{"question":101,"answer":102},"\u003Cp>Which enzyme adds nucleotides during DNA replication?\u003C\u002Fp>","\u003Cp>DNA polymerase adds nucleotides. In bacteria, the main synthesizing enzyme is DNA polymerase III, which reads the template strand and positions each matching nucleotide onto the growing new strand, building it in the 5′ to 3′ direction.\u003C\u002Fp>",{"question":104,"answer":105},"\u003Cp>Are the enzymes the same in prokaryotes and eukaryotes?\u003C\u002Fp>","\u003Cp>The jobs are the same, but the enzyme names differ and do not match one-to-one. Bacterial DNA polymerase III is the main replicase, while in eukaryotes that role is split between DNA polymerases δ and ε, and the primer is made by DNA polymerase α. Do not map the two sets by number.\u003C\u002Fp>",[39],{"slug":108,"title":109,"description":110,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":111,"lastUpdatedDate":45,"draft":46,"category":47,"image":42,"faq":112,"tags":137},"dna-transcription","DNA Transcription: Steps and Mechanism","\u003Cp>Transcription is how a cell copies a gene from DNA into RNA. Learn the steps (initiation, elongation, termination), the template versus coding strand, the Pribnow box, and how transcription ends.\u003C\u002Fp>","2022-07-11",[113,116,119,122,125,128,131,134],{"question":114,"answer":115},"\u003Cp>What is DNA transcription in simple terms?\u003C\u002Fp>","\u003Cp>Transcription is the process by which a cell makes an RNA copy of a gene from DNA. An enzyme called RNA polymerase reads one strand of the DNA and builds a matching strand of RNA. This RNA copy then carries the gene's instructions to be used for making proteins.\u003C\u002Fp>",{"question":117,"answer":118},"\u003Cp>What are the three steps of transcription?\u003C\u002Fp>","\u003Cp>Initiation (RNA polymerase binds the promoter and the DNA opens), elongation (RNA polymerase moves along the template and builds the RNA), and termination (the RNA is completed and released).\u003C\u002Fp>",{"question":120,"answer":121},"\u003Cp>What is the difference between the template strand and the coding strand?\u003C\u002Fp>","\u003Cp>The template strand is the DNA strand that RNA polymerase reads to build the RNA. The coding strand is the other strand, which is not read. The RNA that is made matches the coding strand's sequence, except that uracil (U) replaces thymine (T).\u003C\u002Fp>",{"question":123,"answer":124},"\u003Cp>Which enzyme carries out transcription?\u003C\u002Fp>","\u003Cp>RNA polymerase. In bacteria, a single RNA polymerase makes all types of RNA. In eukaryotes, there are three main RNA polymerases (I, II, and III), each making different types of RNA.\u003C\u002Fp>",{"question":126,"answer":127},"\u003Cp>Does transcription need a primer?\u003C\u002Fp>","\u003Cp>No. Unlike DNA replication, transcription does not need a primer. RNA polymerase can start a new RNA strand on its own.\u003C\u002Fp>",{"question":129,"answer":130},"\u003Cp>What is the Pribnow box?\u003C\u002Fp>","\u003Cp>The Pribnow box is a short DNA sequence (TATAAT) found in bacterial promoters, about 10 bases before the transcription start site (the -10 position). It helps RNA polymerase, guided by its sigma factor, recognize where to begin transcription.\u003C\u002Fp>",{"question":132,"answer":133},"\u003Cp>How does transcription end in bacteria?\u003C\u002Fp>","\u003Cp>In two ways. Rho-dependent termination uses a protein called rho that moves along the RNA and releases it from the polymerase. Rho-independent termination happens when the new RNA forms a GC-rich hairpin loop that causes the RNA to detach on its own.\u003C\u002Fp>",{"question":135,"answer":136},"\u003Cp>What is the difference between transcription and translation?\u003C\u002Fp>","\u003Cp>Transcription copies a gene from DNA into RNA. Translation reads that RNA to build a protein. Transcription comes first and happens in the nucleus in eukaryotes; translation follows and happens at the ribosome.\u003C\u002Fp>",[39],{"enabled":139,"threads":140,"total":141},true,[],0,[143,149,156,163,169,174,180,185,191,194,201],{"slug":144,"name":43,"description":145,"image":146,"body":147,"postCount":148},"acharya-tankeshwar","Editor-in-chief","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Ftankeshwar-acharya-author-microbeonline.jpg","***Tankeshwar Acharya, MSc (Medical Microbiology)***\n\n*Tankeshwar Acharya is an Assistant Professor in the Department of Microbiology at Patan Academy of Health Sciences (PAHS), Nepal, where he has been teaching and practicing clinical microbiology for over 14 years. He is the founder of Microbe Online, one of the leading free microbiology education resources on the web, covering bacteriology, mycology, parasitology, immunology, and clinical laboratory diagnostics written from direct experience in both the classroom and the diagnostic laboratory.*",481,{"slug":150,"name":151,"description":152,"image":153,"body":154,"postCount":155},"ashma-shrestha","Ashma Shrestha","SEO Copywriter and Science Communicator\nKathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fashma-shrestha.png","Ashma Shrestha holds a Master of Science in Medical Microbiology from the Institute of Science and Technology (IOST), Tribhuvan University, Nepal, where she developed a strong foundation in virology, molecular biology, and diagnostic microbiology.\n\nShe now works as an SEO Copywriter at Resolution Digital, where she combines her scientific training with research-driven content strategy. She is certified in Google Analytics and Google Business Profile (GBP), and brings a data-informed approach to science communication writing content that is not only accurate but structured to reach and serve the students who need it most.\n\nAt microbeonline, Ashma contributes articles primarily in virology and molecular biology, areas she finds most compelling for their mechanistic depth and their growing clinical relevance. Her writing reflects the same standard the site is built on: factual rigor, clear explanation of the *why* behind microbiology concepts, and content that helps students move from memorization to genuine understanding.\n\nShe is passionate about making complex microbiological concepts accessible without sacrificing accuracy; a skill that sits at the intersection of her scientific training and her professional work in content and SEO.",79,{"slug":157,"name":158,"description":159,"image":160,"body":161,"postCount":162},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsushmita-baniya-1.png","Sushmita Baniya holds an M.Sc. in Medical Microbiology from Tribhuvan University (National College), with a research focus in Genetics and Molecular Biology. She is actively involved in teaching and research in the field of microbiology.",26,{"slug":164,"name":165,"description":159,"image":166,"body":167,"postCount":168},"samikshya-acharya","Samikshya Acharya","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsamikshya-acharya.jpeg","Samikshya Sharma completed her postgraduate studies in Medical Microbiology at the Central Department of Microbiology, Tribhuvan University, Nepal. She contributes to Microbeonline with the goal of making foundational and clinical microbiology concepts clear and useful for students in medical, laboratory science, and allied health programs.",20,{"slug":170,"name":171,"description":159,"image":42,"body":172,"postCount":173},"alisha-tripathi","Alisha Tripathi","Alisha Tripathi holds an M.Sc. in Medical Microbiology from National College, Tribhuvan University. With over a year of teaching experience, her academic interests span Molecular Biology, Immunology, and Genetics.",6,{"slug":175,"name":176,"description":177,"image":42,"body":178,"postCount":179},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor","Aastha Shrestha is a Biotechnology graduate with an M.Sc. from National College, Tribhuvan University. Her academic interests center on Molecular Biology and Immunology; two fields that are increasingly converging in modern diagnostic and clinical microbiology. \n\nShe contributes to Microbeonline with the goal of making complex concepts in these areas approachable and exam-relevant for students across medical, biotechnology, and laboratory science programs.",9,{"slug":181,"name":182,"description":183,"image":42,"body":42,"postCount":184},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":186,"name":187,"description":159,"image":188,"body":189,"postCount":190},"srijana-khanal","Srijana Khanal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsrijana-khanal-1.png","Srijana Khanal is a microbiology educator with nearly a decade of teaching experience, including her role as faculty in the Microbiology Department at National College, NIST. \n\nHer time in the classroom has given her a clear sense of where students struggle and what explanations actually work, a perspective that directly shapes how she writes.\n\nHer academic interests span Immunology, Genetics, Basic Sciences, and Research Methodology, and she brings the same rigor to her writing that she brought to teaching. Alongside academic writing, she has a passion for creative writing -- an instinct that shows in her ability to make dense scientific material readable without sacrificing accuracy.\n\nShe contributes to Microbeonline to extend her teaching reach beyond the classroom, helping medical and laboratory science students across the region build a stronger foundation in microbiology.",15,{"slug":192,"name":193,"description":183,"image":42,"body":42,"postCount":184},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":195,"name":196,"description":197,"image":198,"body":199,"postCount":200},"nisha-rijal","Nisha Rijal","Microbiologist and AMR Specialist Kathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fnisha-rijal-1.png","Nisha Rijal is a microbiologist with nearly 15 years of frontline diagnostic and surveillance experience at the National Public Health Laboratory (NPHL), national reference laboratory under the Department of Health Services, Nepal. She currently works as an AMR Support Officer at the World Health Organization (WHO), Nepal, where her work focuses on strengthening antimicrobial resistance surveillance systems and translating AMR data into actionable public health response.\n\nHer research, published in peer-reviewed journals and cited over 220 times, spans some of the most clinically significant infectious disease challenges in Nepal and South Asia: antimicrobial resistance trends in *Vibrio cholerae* across an 11-year national surveillance dataset, sero-epidemiology of scrub typhus in patients with acute febrile illness, lower respiratory tract infections in HIV-positive patients, and gonococcal resistance surveillance. She was a contributor to Nepal's National Antimicrobial Resistance Containment Action Plan, a foundational policy document for AMR governance in Nepal. You can find list of [Nisha Rijal's article here in Google Scholar.](https:\u002F\u002Fscholar.google.com\u002Fcitations?user=N-Ruq54AAAAJ&hl=en)\n\nThis depth of experience is visible in her writing at Microbeonline. Her 53 published articles cover bacteriology, parasitology, mycology, immunology, and laboratory techniques, and are consistently among the most detailed and clinically grounded content on the site. She brings to every article the same standard that national reference laboratory work demands: methodological precision, awareness of real diagnostic constraints, and an understanding of what results actually mean for patient care in resource-limited settings.\n\nHer areas of particular expertise include antimicrobial susceptibility testing and resistance mechanism detection, quality assurance in clinical microbiology, and laboratory-based infectious disease surveillance.\n\n---\n\n*Nisha Rijal contributes to Microbeonline in a personal capacity. Her views and writing do not represent the positions of the World Health Organization or any other institution.*",54,{"slug":202,"name":203,"description":204,"image":205,"body":206,"postCount":184},"padma-shrestha","Padma Shrestha","Author","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fpadma-shrestha.png","Padma Shrestha is from Kathmandu, Nepal. She has completed Masters degree in Medical microbiology from Tribhuvan University. She has great interest in Microbiology and Molecular Biology.",[208,215,221,226,231,236,240,244,248,253,257,262,266,271,276,280,284,288,293,298,302,306,310,315,319,323,327,331,336,341,345,349,353,358,362,366,370,374,378,382,386,390,394,398,402,406,410,414,419,423,427,431,435,439,443,447,451,455,459,463,467,471,475,479,483,486,490,494,497,501,504,507,510,513,516,519,522,525,528,531,534,537,540],{"slug":209,"name":210,"description":211,"image":212,"body":213,"postCount":214},"gram-negative-cocci","Gram-Negative Cocci and Coccobacilli","Neisseria, Moraxella, Haemophilus and related gram-negative coccal organisms","https:\u002F\u002Fassets.microbeonline.com\u002Ftags\u002Fgram-negative-cocci.png","# Gram Negative Cocci\n\nNeisseria gonorrhoeae, Neisseria meningitides, Moraxella catarrhalis, and other Neisseria spp. are clinically relevant gram-negative cocci.\n\nN. gonorrhoeae is the leading cause of sexually transmitted disease whereas N. meningitides is a leading cause of fatal bacterial meningitis.",14,{"slug":216,"name":217,"description":218,"image":42,"body":219,"postCount":220},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":222,"name":223,"description":224,"image":42,"body":42,"postCount":225},"gram-positive-cocci","Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":227,"name":228,"description":229,"image":42,"body":42,"postCount":230},"gram-negative-rods","Gram-Negative Rods (Other than Enterobacteriaceae)","\u003Cp>Gram negative rods other than members of Enterobacteriaceae family such as  Pseudomonas, Acinetobacter and related organisms\u003C\u002Fp>",5,{"slug":232,"name":233,"description":234,"image":42,"body":42,"postCount":235},"gram-positive-rods","Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":237,"name":238,"description":239,"image":42,"body":42,"postCount":225},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":241,"name":242,"description":243,"image":42,"body":42,"postCount":220},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":245,"name":246,"description":247,"image":42,"body":42,"postCount":220},"enterobacteriaceae","Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":249,"name":250,"description":251,"image":42,"body":42,"postCount":252},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":254,"name":255,"description":256,"image":42,"body":42,"postCount":214},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":258,"name":259,"description":260,"image":42,"body":42,"postCount":261},"antimicrobial-susceptibility-testing","Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":263,"name":264,"description":265,"image":42,"body":42,"postCount":214},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":267,"name":268,"description":269,"image":42,"body":42,"postCount":270},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":272,"name":273,"description":274,"image":42,"body":42,"postCount":275},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":277,"name":278,"description":279,"image":42,"body":42,"postCount":261},"bacterial-structure-physiology","Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":281,"name":282,"description":42,"image":42,"body":283,"postCount":173},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":285,"name":286,"description":42,"image":42,"body":287,"postCount":270},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":289,"name":290,"description":291,"image":42,"body":292,"postCount":252},"electrophoresis","Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":294,"name":295,"description":296,"image":42,"body":297,"postCount":173},"pcr-techniques","PCR Techniques","Information about various types of Polymerase Chain Reaction Techniques ","More detailed information about various types of Polymerase Chain Reaction Techniques ",{"slug":299,"name":300,"description":301,"image":42,"body":42,"postCount":173},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":303,"name":304,"description":305,"image":42,"body":42,"postCount":173},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":307,"name":308,"description":309,"image":42,"body":42,"postCount":173},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":311,"name":312,"description":313,"image":42,"body":42,"postCount":314},"immunoassays","Immunoassays","You will get information about all the diagnostic tests that rely on the specific binding between an antigen and an antibody to detect or quantify a substance.",19,{"slug":316,"name":317,"description":318,"image":42,"body":42,"postCount":252},"biosafety-levels","Biosafety levels ","Articles related to Biosafety Levels",{"slug":320,"name":321,"description":322,"image":42,"body":42,"postCount":230},"environmental-factors","Environmental Factors ","In this case we are talking about growth requirements of microorganisms with deep dive in environmental factors that affect the growth. ",{"slug":324,"name":325,"description":326,"image":42,"body":42,"postCount":173},"pipette","Pipette","Posts related with Pipette. ",{"slug":328,"name":329,"description":330,"image":42,"body":42,"postCount":235},"bacteriology-mcqs","Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":332,"name":333,"description":334,"image":42,"body":42,"postCount":335},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":337,"name":338,"description":339,"image":42,"body":42,"postCount":340},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":342,"name":343,"description":344,"image":42,"body":42,"postCount":230},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":346,"name":347,"description":348,"image":42,"body":42,"postCount":235},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":350,"name":351,"description":352,"image":42,"body":42,"postCount":270},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":354,"name":355,"description":356,"image":42,"body":42,"postCount":357},"bacterial-culture-media","Bacterial Culture Media","Posts related to Bacterial Culture Media. ",23,{"slug":359,"name":360,"description":361,"image":42,"body":42,"postCount":173},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":363,"name":364,"description":365,"image":42,"body":42,"postCount":230},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":367,"name":368,"description":369,"image":42,"body":42,"postCount":270},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":371,"name":372,"description":373,"image":42,"body":42,"postCount":335},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":375,"name":376,"description":377,"image":42,"body":42,"postCount":340},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":379,"name":380,"description":381,"image":42,"body":42,"postCount":252},"bacterial-classification","Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":383,"name":384,"description":385,"image":42,"body":42,"postCount":230},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":387,"name":388,"description":389,"image":42,"body":42,"postCount":179},"antibody-mediated-immunity","Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":391,"name":392,"description":393,"image":42,"body":42,"postCount":252},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":395,"name":396,"description":42,"image":42,"body":42,"postCount":397},"haemophilus","Haemophilus",3,{"slug":399,"name":400,"description":401,"image":42,"body":42,"postCount":340},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":403,"name":404,"description":405,"image":42,"body":42,"postCount":220},"adaptive-immunity","Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":407,"name":408,"description":409,"image":42,"body":42,"postCount":214},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":411,"name":412,"description":413,"image":42,"body":42,"postCount":230},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":415,"name":416,"description":417,"image":42,"body":418,"postCount":173},"laboratory-heating-equipment","Laboratory Heating Equipment","A guide to laboratory heating equipment, including hot plates, water baths, Bunsen burners, incubators, and dry baths, and how to choose the right one for each task.","Laboratory heating equipment covers the instruments that warm, melt, incubate, or sterilize samples and media in a microbiology laboratory. Each one delivers heat differently. \n\nA hot plate gives high, direct, dry heat; a water bath gives gentle, even, wet heat up to about 100°C; a Bunsen burner gives an open flame for rapid, very high heat; an incubator holds cultures at a steady temperature over hours or days; and a dry bath heats small tubes without water. Choosing the right one depends on the temperature you need, how precise it must be, and whether the sample can tolerate direct or open-flame heat.\n\nThe articles below cover each piece of heating equipment in detail, including its parts, working principle, uses, and the mistakes that most often go wrong at the bench.",{"slug":420,"name":421,"description":422,"image":42,"body":42,"postCount":179},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":424,"name":425,"description":426,"image":42,"body":42,"postCount":173},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":428,"name":429,"description":430,"image":42,"body":42,"postCount":252},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":432,"name":433,"description":434,"image":42,"body":42,"postCount":184},"tests-for-gram-positive-cocci","Biochemical Tests for Gram Positive Cocci","This is the lists of Biochemical Tests that are used for Gram Positive Cocci. ",{"slug":436,"name":437,"description":438,"image":42,"body":42,"postCount":270},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":440,"name":441,"description":442,"image":42,"body":42,"postCount":261},"enzyme-tests","Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":444,"name":445,"description":446,"image":42,"body":42,"postCount":225},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":448,"name":449,"description":450,"image":42,"body":42,"postCount":230},"susceptibility-based-id","Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":452,"name":453,"description":454,"image":42,"body":42,"postCount":340},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":456,"name":457,"description":458,"image":42,"body":42,"postCount":235},"substrate-utilization","Substrate Utilization","\u003Cp>The test in which a non-sugar carbon\u002Fnitrogen source is used or degraded (citrate, malonate, decarboxylases, indole, PAD).\u003C\u002Fp>",{"slug":460,"name":461,"description":462,"image":42,"body":42,"postCount":397},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":464,"name":465,"description":466,"image":42,"body":42,"postCount":230},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":468,"name":469,"description":470,"image":42,"body":42,"postCount":252},"innate-immunity","Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":472,"name":473,"description":474,"image":42,"body":42,"postCount":340},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":476,"name":477,"description":478,"image":42,"body":42,"postCount":230},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":480,"name":481,"description":482,"image":42,"body":42,"postCount":235},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":39,"name":484,"description":485,"image":42,"body":42,"postCount":173},"DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":487,"name":488,"description":489,"image":42,"body":42,"postCount":252},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":491,"name":492,"description":493,"image":42,"body":42,"postCount":252},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":495,"name":496,"description":42,"image":42,"body":42,"postCount":184},"colorimetric-assay","Colorimetric Assay ",{"slug":498,"name":499,"description":500,"image":42,"body":42,"postCount":230},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":502,"name":503,"description":42,"image":42,"body":42,"postCount":397},"blood-and-immune-cells","Blood and Immune Cells",{"slug":505,"name":506,"description":42,"image":42,"body":42,"postCount":230},"host-pathogen-interaction","Host Pathogen Interaction",{"slug":508,"name":509,"description":42,"image":42,"body":42,"postCount":340},"blood-culture","Blood Culture",{"slug":511,"name":512,"description":42,"image":42,"body":42,"postCount":340},"environmental-microbiology","Environmental microbiology ",{"slug":514,"name":515,"description":42,"image":42,"body":42,"postCount":173},"copromicroscopic-technique","Copromicroscopic Technique",{"slug":517,"name":518,"description":42,"image":42,"body":42,"postCount":397},"quality-control","Quality Control",{"slug":520,"name":521,"description":42,"image":42,"body":42,"postCount":340},"dermatophytes","Dermatophytes",{"slug":523,"name":524,"description":42,"image":42,"body":42,"postCount":397},"viral-hemorrhagic-fevers","Viral Hemorrhagic Fevers",{"slug":526,"name":527,"description":42,"image":42,"body":42,"postCount":340},"h2s-production","H2S Production",{"slug":529,"name":530,"description":42,"image":42,"body":42,"postCount":335},"water-quality-testing","Water Quality Testing",{"slug":532,"name":533,"description":42,"image":42,"body":42,"postCount":230},"virology-basics","Virology basics",{"slug":535,"name":536,"description":42,"image":42,"body":42,"postCount":340},"typing-methods","Typing Methods",{"slug":538,"name":539,"description":42,"image":42,"body":42,"postCount":397},"blotting-technique","Blotting Technique",{"slug":541,"name":542,"description":42,"image":42,"body":42,"postCount":340},"history-microbiology","History of Microbiology"]