Microbial Growth and Culturing

Vocabulary

acidophile

organism that grows in acidic (low pH of usually 2 or below) conditions

aerotolerant anaerobe

organism that thrives in the absence of oxygen but is not harmed by the presence of oxygen

agar

mixture of two sugars that produces a gelatin-like surface and provides a base for a variety of different growth media

alkaliphile

organism that grows in basic (high pH of usually 8.5–11) conditions

barophile

microbe that lives in conditions of high hydrostatic pressure

binary fission

process by which cells divide asexually

budding

type of cell division in which the daughter cell develops from a bud growing off the mother cell

colony

visible mass of microbes originating from the replication of a single microbe

colony-forming unit (CFU)

each viable microorganism in a sample that is capable of enough replication to form a visible colony

differential media

media containing ingredients that allow for distinguishing bacteria with a visual cue

endospore

toughened, condensed form of cell that can withstand harsh environmental conditions and is formed completely within the bacterial cell and is released when the cell dies

exospore

spore that begins to form within the bacterial cell and the final encapsulation step occurs by budding

facultative

describes an organism that is able to tolerate an environment with or without specific properties

facultative anaerobe

organism capable of aerobic and anaerobic respiration

generation time

amount of time it takes for a population to double in size

hydrostatic pressure

pressure a fluid exerts on points below its surface

medium

substance containing nutrients that support the growth of cells

mesophile

organism that grows at temperatures between 20°C and 45°C

microaerophile

organism that requires oxygen but can only survive in low-oxygen conditions

neutrophile

organism that grows in neutral pH (between 6.5–7.5) conditions

obligate

describes an organism that has a strict requirement for specific factors in order to survive

obligate aerobe

organism that requires oxygen for survival

obligate anaerobe

organism that dies in the presence of oxygen

pour plate

microbe sample that is mixed with the liquid agar before pouring the plate

psychrophile

organism that grows best at temperatures below 20°C

selective media

media designed to support the growth of specific microbes while preventing others from growing

serial dilution

stepwise reduction of a culture population into increasing proportions of a solution

sporulation

formation of spores

spread plate

microbe sample that is placed in contact with the solid agar surface

thermophile

organism that grows best at temperatures between 41°C and 80°C