Brock's Microbes Chapter 5

Acidophile

an organism that grows best at low pH, typically below pH 5.5

Aerobe

an organism that can use O2 in respiration; some require O2

Aerotolerant

anaerobe a microorganism unable to respire O2 but whose growth is unaffected by it

Alkaliphile

an organism that has a growth pH optimum of 8 or higher

Anaerobe

an organism that cannot use O2 in respiration and whose growth is typically inhibited by O2

Antimicrobial agent

a chemical compound that kills or inhibits the growth of microorganisms

Antiseptic (germicide)

a chemical agent that kills or inhibits growth of microorganisms and is sufficiently nontoxic to be applied to living tissues

Aseptic technique

a series of steps taken to prevent contamination of laboratory cultures and media

Autoclave

a sealed heating device that destroys microorganisms with temperature and steam under pressure

Bactericidal agent

an agent that kills bacteria

Bacteriostatic agent

an agent that inhibits bacterial growth

Batch culture

a closed-system microbial culture of fixed volume

Binary fission

cell division following enlargement of a cell to twice its minimum size

Biofilm

an attached polysaccharide matrix containing bacterial cells

Budding division

a cell division process whereby new cell material is produced from a single point instead of along the entire cell

Cardinal temperatures

the minimum, maximum, and optimum growth temperatures for a given organism

Chemostat

a device that allows for the continuous culture of microorganisms with independent control of both growth rate and cell number

Compatible solute

a molecule that is accumulated in the cytoplasm of a cell for adjustment of water activity but that does not inhibit biochemical processes

Complex medium

a culture medium of highly nutritious substances for which the exact composition is unknown

Culture medium

a nutrient solution required for growing a laboratory culture of a specific microorganism

Defined medium

a culture medium for which the exact composition is known

Disinfectant

an antimicrobial agent used only on inanimate objects

Disinfection

rendering a surface or object free of all pathogenic microorganisms

Exponential growth

growth of a microbial population in which cell numbers double within a specific time interval

Extreme halophile

a microorganism that requires very large amounts of NaCl, usually greater than 10% and in some cases near saturation, for growth

Facultative

with respect to O2, an organism that can grow in either its presence or absence

Generation time

the time required for a population of microbial cells to double

Germicide (antiseptic)

a chemical agent that kills or inhibits growth of microorganisms and is sufficiently nontoxic to be applied to living tissues

Growth

in microbiology, an increase in cell number

Halophile

a microorganism that requires NaCl for growth

Halotolerant

a microorganism that does not require NaCl for growth but can grow in the presence of NaCl, in some cases, substantial levels of NaCl

Hyperthermophile

a species of Bacteria or Archaea whose growth temperature optimum is 80°C or greater

Mesophile

an organism that grows best at temperatures between 20 and 40°C

Microaerophile

an aerobic organism that can grow only when O2 tensions are reduced from that present in air

Minimum inhibitory concentration (MIC)

the minimum concentration of a substance necessary to prevent microbial growth

Neutrophile

an organism that grows best at neutral pH, between pH 5.5 and 8

Obligate anaerobe

an organism that cannot grow in the presence of O2

Osmophile

an organism that grows best in the presence of high levels of solute, typically a sugar

Pasteurization

the heat treatment of milk or another liquid to reduce its total number of microorganisms

pH

the negative logarithm of the hydrogen ion (H+) concentration of a solution

Plate count

a method for counting viable cells; the number of colonies on a plate is used as a measure of cell numbers

Psychrophile

an organism with a growth temperature optimum of 15°C or lower and a maximum growth temperature below 20°C

Psychrotolerant

capable of growing at low temperatures but having an optimum above 20°C

Sanitizer

an agent that reduces microorganisms to a safe level, but may not eliminate them

Sterilant

a chemical agent that destroys all forms of microbial life

Sterilization

the killing or removal of all living organisms and viruses

Thermophile

an organism whose growth temperature optimum lies between 45 and 80°C

Viable

capable of reproducing

Viable count

a measurement of the concentration of live cells in a population

Water activity

the ratio of the vapor pressure of air in equilibrium with a solution to the vapor pressure of pure water

Xerophile

an organism that is able to live, or that lives best, in very dry environments