The microbiology laboratory deals with detecting, culturing, and identifying microorganisms like bacteria, fungi, viruses, etc. Some of the requirements of microbiological laboratories are essential equipment/instruments, trained human resources, maintaining personal safety, sanitation of the working area, and regular equipment maintenance.
Equipment Commonly Used in Microbiology Laboratory
Human resources, along with the equipment, will make any laboratory work more effortless. There are many must-have pieces of equipment and instrument for microbiology laboratories. Some of them are as follows:
Equipment used for sterilization
The autoclave is an example of moist heat sterilization. The primary purpose of the autoclave is sterilizing culture media and laboratory supplies. Saturated steam under pressure above 100℃ is used for sterilization in autoclaves. There are many autoclaves, but the most common type is the pressure cooker laboratory autoclave.
Hot Air Oven
A hot air oven applies dry heat for sterilization. Its main application is sterilizing glassware like pipettes, flasks, metallic instruments, and scissors. Electric current provides heat in a hot air oven. The heat is provided uniformly due to the arrangement of heating elements. The holding time depends on temperature.
A clinical microbiology laboratory produces hazardous wastes that need to be destroyed appropriately. An incinerator is the best way to discard those dangerous waste. Incinerators use heat to eliminate solids; powder, pastes, pills, sludges, liquids, boxes, and tubes. This instrument is the best substitute for disposal because it can destroy large amounts of waste at a time without much manual labor.
It is the microbiological laboratory equipment used for sterilization. The instrument uses high temperature for discarding small metal utensils like lancets, needles, inoculating loops, and forceps. It requires less time and can be a suitable replacement for Bunsen burners and alcohol lamps.
Instruments for Culture and Identification
An analytical balance measures the precision in determining the mass of solid objects, liquids, powders, and granular substances. It is an electronic device and uses the principle of magnetic force restoration, offering readability up to 0.0001 g.
Biological Safety Cabinets
A microbiology laboratory deals with many infectious and hazardous organisms and different carcinogenic chemicals. There is a very high risk of contaminating the environment and personnel in the microbiology laboratory. Thus the need for safe and contamination-free transfer of specimens, daily practice in the microbiology laboratory, has arisen. The biological safety cabinet is the principal device used for containment while dealing with microbiological samples.
The cabinets are differentiated into different levels depending on the types of organisms handled in the laboratory. Biosafety levels (BSL) provide conditions for safely handling the organism. There are four different biosafety levels; BSL1, BSL2, BSL3, and BSL4. BSL4 handles the most dangerous organisms which cause life-threatening diseases, whereas BSL1 handles organisms that can cause mild infections.
The Bunsen burner is a gas burner that uses dry heat to sterilize materials. The highest temperature it can provide is 1870℃. The materials are heated by holding them almost vertically in the flame until red hot. The Bunsen burner usually requires gas (cooking gas). The use of the Bunsen burner is sterilizing the materials like inoculating loop needles, the tip of forceps, and spatula. Similarly, a Bunsen burner creates a sterile zone. Bunsen burner can be used to flam the mouths of tubes and flasks before and after use and remove gas bubbles formed during pouring media.
A centrifuge is a laboratory device that helps separate fluids, gas, or liquid-based on their density. The spinning of a vessel containing material at high speed helps achieve the separation. The application of this equipment in many laboratories is in purifying cells, subcellular organelles, viruses, proteins, and nucleic acids. The high speed creates centrifugal force. Thus, pushing the heavier material onto the outer part of the vessels. The centrifuge is of different types based on its intended use or motor. Some of them are; benchtop centrifuges, refrigerated benchtops centrifuges, clinical benchtop centrifuges, microcentrifuges, and vacuum centrifuges.
Chromatography is a technique that assists in separating and analyzing complex mixtures. It consists of a mobile phase that carries the mixture and passes it to the stationary phase. The speed of travel of materials is different because of their difference in migration rate. The equipment of chromatography includes columns, freits, flow cells, pumps, detectors, collectors, and complete systems used in high-performance liquid chromatography (HPLC), gas chromatography (GC), and liquid chromatography-mass spectrometers (LC-MS).
A colony counter is a machine that automatically counts colonies in the agar plate in the microbiology laboratory. It uses fluorescent labels or the contrast between light and dark areas on the plate to measure the colonies. It has replaced the conventional counting method in most laboratories, manual counting.
Gel Electrophoresis Apparatus
Electrophoresis is a process that separates nucleic acid and protein-based on their size and charge. It requires a set of different types of apparatus and equipment. There are two basic types of electrophoresis instruments available; horizontal and vertical. Both types require almost the same set of instruments. The difference is the placement of samples in vertical type is on the top of the gel, whereas in horizontal type, it is in a well on one side of the gel. The vertical gel electrophoresis instrument is preferred because it can process smaller fragments of DNA and many samples at a time.
Electrodes, electrophoresis chambers, casting tray, polyacrylamide, agarose, buffers, and comb are the instruments necessary for electrophoresis.
A homogenizer is an instrument that helps in obtaining a uniform and consistent mixture. It breaks down the component so that the distribution is even throughout the solution. The substance in the mix is either immiscible, has different sizes, or is in distinct phases from each other. Aside from homogenizing the solution, the instrument functions in emulsifying, suspending, grinding, dispersing, and dissolving the substances.
A hot plate provides heat to solutions and materials uniformly. It is much safer than a Bunsen burner because an open flame is not present in the hot plate. In the microbiology laboratories, hot plate serves their purpose in making agar media and biochemical media. Based on materials used to make the plate of the hot plate, it is of many types. Some of the materials most commonly used in making the plate are aluminum, glass, and ceramic.
Here, aluminum is a good conductor of heat, and a hot plate heats quickly and evenly, but it is susceptible to rusting and degradation after heating the corrosive materials. However, ceramic is resistant to corrosion and viewing of samples of possible due to the light coloration of the materials. But it can crack if handled roughly and incorrectly. Likewise, glass material is also resistant to corrosion, heats effectively, and observation of samples is easy. In addition, glass decreases the chance of transferring heat beyond the glass, reducing accidental burns.
An incubator is an instrument that provides the desired temperature for in vitro culture of microorganisms. It consists of a double-walled chamber made up of metal sheets. The front part of the chamber has a glass door. A thermostat controls the incubator’s temperature and turns off the heat supply until the incubator reaches the required temperature. It also contains a thermometer in the vent that records the temperature. There are many types of incubators used in microbiology. They are benchtop incubators, CO2 incubators, potable incubators, shaker incubators, and cooled incubators.
A Laboratory freezer is used to store samples, specimens, and other materials at -10℃ to -30℃. A general purpose laboratory freezer can typically store samples up to -25℃ whereas ultra low-temperature freezer can freeze samples to almost -80℃.
Laminar Flow Cabinet
A laminar flow chamber is a safety cabinet. Laminar flow is the unidirectional air moving at a steady velocity along parallel lines. A laminar flow cabinet can be used in laboratories where the risk of handling hazardous organisms is significantly low. HEPA (high-efficiency particulate air) filter removes particles, including microorganisms, from the air. This chamber aims to prepare sterile media, assemble those media into complete units, and transfer materials aseptically.
Most microorganisms are not visible under the naked eye. A microscope is an optical instrument that consists of a lens or combination of lenses that makes an enlarged image of minute objects. There are two types of microscopes depending on their principle; light microscope and electron microscope. The light microscope comprises four types: bright field, dark field, fluorescence, and phase-contrast.
In contrast, an electron microscope is divided into only two types; transmission electron microscope and scanning electron microscope. A microscope has different parts: Eyepiece, condenser, objective, stage, condenser, diaphragm, light source, and adjustment knobs.
Micropipettes are semi-automatic instruments that use disposable pipette tips to withdraw and dispense the liquid sample. This helps to avoid the risk of human contamination in the laboratory and also get a precise measurement of the reagent and sample.
Thermocyclers are the instrument that helps in amplifying DNA and RNA samples by the process of polymerase chain reaction (PCR). The thermocycler controls the temperature of the specimens in a holding block by preprogrammed steps. It then allows the denaturation and reannealing of samples with various reagents. The amplified gene can then be used in cloning, sequencing, genotyping, and analyzing the sample.
A pH meter measures the acidity/alkalinity of the solution. It detects the activity of hydrogen ions in the solution. The degree of activity of hydrogen ions in the solution is the pH level of the solution, i.e., the higher the activity of hydrogen ions, the higher the pH level of the solution.
The refrigerator provides a low-temperature environment. Refrigerator preserves those materials and stock culture that may decompose and destroy when kept at room temperature. The most commonly used refrigerator is a domestic refrigerator of about 1-2 m3 or even larger. The ideal temperature for refrigeration is 4-5℃, and some refrigerators may also contain a freezer that provides -20 to -40℃. The use of refrigerators is to store cultures, media prepared, blood, serum, antibiotics, and other chemicals.
A spectrophotometer is an instrument that measures the number of photons absorbed after it passes through the sample solution. A spectrophotometer is of two types based on the wavelength of the light source; UV-visible and IR spectrophotometer.
The spectrophotometer consists of two devices: a spectrometer and a photometer. A spectrometer produces light of the desired wavelength. At the same time, a photometer detects the number of photons absorbed by the solution and displays the amount.
A vortex mixer mixes laboratory samples in test tubes, well plates, or flasks. A motorized drive shaft is present below the sample platform, which oscillates rapidly and transfers the orbital motion to the sample container loaded into the mixer. This motion causes the sample to circulate and undergo a turbulent flow known as a vortex. It is similar to the kinetic force of stirring, but its advantage is the mixing of samples in a sealed container, and the mixing of at least two specimens at a time is possible.
A water bath is an instrument that provides constant temperature to a sample. A thermostat controls the water bath’s temperature. It consists of an insulating box of steel and electrodes to provide warmth. Its uses in microbiology are in incubation, media preparation, and maintaining temperature.
Identification of microbe also requires performing serological tests especially in diagnosing viruses. The following instruments are required for serological tests:
- ELISA Test Kit: ELISA (enzyme-linked immunosorbent assay) kit comes with the reagents required for the test, plates with multiple wells pre-coated with captured antibody/antigen, standards and buffer to perform the test.
- ELISA plate reader: It is the laboratory instrument that helps in reading the fluorescence, luminescence, or chromogenic reaction in the 96 well plates after performing ELISA.
Instruments for Antibiotic Susceptibility Testing
Antibiotic Disc Dispenser
The antibiotic disc dispenser is the laboratory equipment that helps accurately place the antibiotic disc in the media of choice. It is handy equipment to obtain precision while conducting antibiotic susceptibility testing. It is available in various types based on the number of cartridges and the Petri plate size.
Antibiotic Zone Reader
An antibiotic zone reader is a laboratory instrument that helps to obtain an accurate reading of the diameter of the zone of inhibition of the used antibiotic. It is an automatic method that replaces the tedious and erroneous manual work of reading the zone of inhibition during antibiotic susceptibility testing.
The Kirby Bauer method of antibiotic susceptibility testing requires a standard concentration (MacFarland standard) of bacterial colonies. Densitometer is an automatic laboratory instrument that helps obtain the required concentration of bacterial suspension.
Beaker, conical flask, glass rods, measuring cylinder, microscopic slide, Petri dish, glass pipette, and test tubes are the commonest glassware used in a microbiology laboratory.
A beaker is a glass container that has a flat bottom. The use of beakers in a microbiology laboratory is holding or storing liquids.
A conical flask is a cone-shaped flask with a flat round bottom and a cylindrical neck. It is also called Erlenmeyer’s flask. Its purpose in the microbiology laboratory is to prepare media.
A glass rod is a piece of laboratory equipment used to mix chemicals and liquids. They are made of solid glass with a thickness and length similar to drinking straw. It has rounded ends. Bent glass rods or L-shaped rods spread dilute specimens over the agar surface, whereas straight glass rods are used to stir agar and solution.
A measuring cylinder is an instrument made of glass or plastic used to measure the volume of different liquids. Measuring cylinders are graduated, measuring the volume in ml (milliliter).
Microbiology laboratories use different types of microscopic slides. The most common type is a plain glass slide. It is used in staining and observing under a microscope. The preferred dimension of a plain glass slide is three by one inch with 1 mm thickness. Another type of slide commonly used for hanging drop motility has wells or depression in the center.
Apart from slides, the microbiology laboratory uses coverslips for wet mount preparation for observing parasites.
A Petri dish is made up of glass/plastic. It is an apparatus in which culture media is poured, providing a suitable environment for the growth of microorganisms. Petri dish consists of two look-alike parts, but one is bigger than the other forming a cap-like structure. The preferred diameter of the petri dish is 90 mm.
Pipette is the glassware that helps deliver a specific quantity of fluid from one container to another. A pipette is a piece of a calibrated glass tube marked, and a sample is drawn through a small capillary.
A standard test tube has high utility in the microbiology laboratory. It helps grow microorganisms by providing an artificial environment, preparing stock cultures, and performing various biochemical tests. The microbiology laboratory uses borosilicate glass, and the open end is plain without lips. They have cotton plugs as a stopper, but using metal or plastic caps is possible.
Biochemical media are a unique media or solution that helps study any microorganisms’ biochemical characteristics. The study of biochemical traits is essential for identifying microorganisms, especially bacteria.
Culture media are the artificial nutritional preparation for the culture of bacteria and fungi. The media are classified based on their physical state, chemical composition, and intended use.
Based on the physical state, there are three types of media; solid, liquid, and semi-solid. Similarly, based on chemical composition, there are two types of media; synthetic and non-synthetic. Finally, based on intended use, there are seven types of media; general-purpose media, selective media, differential media, enrichment media, enriched media, transport media, and anaerobic culture media.
Eppendorf tubes are single-purpose tubes made up of polypropylene, and their application is centrifuging, transporting, mixing, and storing liquid/solid samples and reagents.
Inoculating Loop and Needle
An inoculating loop and needle transfer microbial growth from one container to another without introducing any unwanted organisms. Both types of equipment consist of a wooden handle attached to a nichrome or stainless steel wire which may be in a loop or straight.
In conclusion, besides the instruments mentioned above, safety equipment like gloves, hairnets, googles, laboratory aprons, and coats is necessary for handling samples.
A dry bath is a type of laboratory equipment that has application in heating multiple samples held in different test tubes. It can be digital or analog. Based on the blocks that hold the test tube, it is available in various sizes.
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