Microbial Growth: Temperature and Oxygen

MGI 301

obligate aerobe

microorganisms that require oxygen to grow

minimum temperature

lowest temperature at which a bacterium can grow, membranes can gel and enzymes may fail

facultative

microorganisms that prefer to use oxygen, but can utilize other metabolism pathways if not present

mesophile

optimum temperature range of 15°C to 45°C, including common human pathogens

microaerophile

grows in environments where oxygen is present in low concentrations

decimal reduction time

the time required to reduce the number of viable cells by 10-fold

enzyme that detoxifies oxygen byproduct from aerobic respiration

superoxide dismutase

thermophile

grows in optimum temperatures within 45°C to 80°C

oxic zone

high concentrations of oxygen in thioglycolate medium, pink in color because oxygen reacts with resazurin

psychrophile

grows in optimum temperatures within -5°C to 15°C

hyperthermophile

optimum growth temperatures above 80°C

anoxic zone

zone in thioglycolate medium with no/very low oxygen levels, not pink in color

aerotolerant anaerobe

can grow when oxygen is present but does not utilize oxygen for growth

maximum temperature

highest temperature a bacterium can grow, proteins and enzymes denature, membranes fail

obligate anaerobe

can only growth when no oxygen is present

optimal temperature

ideal temperature for a bacterium to grow, maximum growth rate

thioglycolate medium

a nutrient medium that forms and oxygen gradient, used to determine oxygen requirements of a microorganism