Microbial growth is defined as an increase in the number of cells in a population. The mere presence of optimum nutrients is not sufficient to grow microorganisms. Microbial growth is affected by various environmental factors such as:
Organisms that can utilize radiant energy (sunlight) are called phototrophs. Chemotrophs are organisms that can harvest energy from chemicals.
Most microorganisms grow best around neutral pH values (6.5 - 7.0), but some thrive in extreme pH conditions (pH10).
Psychrophiles can grow at 0°C, mesophiles have optimum temperature near 37°C, and thermophiles grow best at 50-60°C.
Typical growth curve of microorganisms in a closed system consists of distinct phases called lag phase, log phase, stationary phase, and death phase.
Microorganisms can be classified as obligate aerobes, facultative, microaerophilic, aerotolerant and obligate anaerobes based on their oxygen requirements.
