Factors Influencing Microbial Growth and Reproduction

Binary Fission

The process through which bacteria reproduce.

Microbial Growth

Refers to the increase in the number of cells, not the size of individual cells.

Minimum Growth Temperature

The lowest temperature at which growth occurs.

Optimum Growth Temperature

The temperature at which growth is most rapid.

Maximum Growth Temperature

The highest temperature at which growth is possible.

Psychrophiles

Cold-loving organisms with an optimum growth temperature of 15°C or lower.

Psychrotrophs

Species that can grow in cold temperatures, with an optimum growth temperature between 20°C and 30°C, but can grow at 0°C to 7°C.

Mesophiles

Includes most bacteria with an optimum growth temperature of 20°C to 45°C.

Thermophiles

Heat-loving organisms with an optimum growth temperature of 55°C to 65°C.

Hyperthermophiles

Organisms that love extreme heat, with an optimum growth temperature of 70°C to 110°C.

Osmotic Pressure

The force water exerts on the semi-permeable membrane (plasma membrane) surrounding the cell.

Hypotonic Environment

The concentration of solute is lower outside the cell than inside, causing water to flow into the cell.

Hypertonic Environment

The concentration of solute is higher outside the cell than inside, leading to water loss from the cell.

Osmotolerant Microorganisms

Can maintain water availability in hypertonic environments by increasing their internal solute concentration.

Halophiles

Bacteria that specifically require a high concentration of sodium chloride (NaCl) to thrive.

Aerobes

Organisms that require atmospheric O₂ for growth.

Anaerobes

Organisms that are killed or inhibited by the presence of atmospheric O₂.

Facultative Anaerobes

Organisms that do not require O₂ for growth but grow better when it is present.

Microaerophiles

Organisms that require low concentrations of O₂, generally between 2% and 10%.

Aerotolerant Anaerobes

Anaerobic organisms that can survive in the presence of O₂ but do not utilize it in their metabolism.

Enzymes

Proteins that act as catalysts, speeding up chemical reactions without being permanently altered or consumed.

Physical factors

Temperature
pH
Osmotic Pressure

Chemical Requirements

Carbon
Nitrogen, sulfur, and phosphorous
Trace elements
Oxygen
growth factor