LECTURE 4 Cultivating & Controlling Microbial Growth

assimilation

process of importing & incorporation of molecules by living cells

essential nutrients

must be provided to organism

macronutrients

needed in large amounts

micronutrients

needed in small amounts

organic nutrients

contain carbon & hydrogen atoms

inorganic nutrients

simple atoms or molecules from non-living matter

prototrophs

organisms that can synthesize all required cell components from one carbon source and inorganic precursors

auxotrophs

organisms require important molecular precursors

media

combination of nutrients used to cultivate microbes

culture

growth of organisms in or on nutrient medium

inoculum

material used to start a culture

mixed culture

a culture that contains two or more known organisms

pure culture (axenic)

a culture that contains only one known organism

subculture

to make a second culture from an isolated colony

colony

macroscopically visible population of cells growing on solid medium

culture medium

substance containing nutrients that support growth of cells or microorganisms

selective medium

inhibits growth of some microbes & selects for the desired microbe

differential medium

allows for growth of several types of microbes

enriched media

contains complex organic substances that a specific species needs for growth

decontamination

methods that destroy, remove or reduce number of undesirable microbes

disinfection

destruction of vegetative pathogens and toxins on inanimate objects

sterilization

complete destruction or inactivation of living organisms and viruses

sepsis

growth of microorganisms in body tissues

asepsis

practices that prevent introduction of infectious organisms into tissue

antiseptics

chemical agents applied to body tissues to destroy or inhibit vegetative pathogens

four stages of growth curve

lag, exponential (log), stationary, death

bactericide

kills bacteria except endospores

bacteristatic

prevents growth of bacteria

microbial death

permanent loss of reproductive capability even under optimum growth conditions

highest resistance

prions & bacterial endospores

moderate resistance

cysts of protozoa & naked viruses over enveloped viruses

least resistance

bacterial vegetative cells, fungus spores & hyphae, yeast, protozoan trophozoites

filtration

used to sterilize heat sensitive liquids or gases

dry heat control

low moisture, dehydrates cells & denatures proteins, takes more time

moist heat control

occurs in hot or boiling water or steam, causes denaturation of proteins, doesn’t allow for complete sterilization

autoclave

sterilization with steam under pressure, circulates boiling eater around objects to be sterilized

pasteurization

where heat is used to reduce microbial population in heat-sensitive foods, doesn’t kill endospores

microbial growth

increase in # of microorganisms