BSCI 263 EXAM2 (Ch. 6- Microbial Growth)

Psychrophiles

Cold loving, Growth at 0C - optimum 15C

Psycotrophs

Type of psychrophile, optimum 20-30C, causes food spoilage in fridge

Mesophiles

Moderate-temp loving, optimum growth at 25-40C, pathogens of animals

Thermophiles

Heat-loving, optimum growth at 50-60C

Hyperthermophiles

Optimum growth at >80C

pH requirements

-Most bacteria grow between 6.5-7.5

-Fermentation produces acids

-Growth media may include buffers

Plasmolysis

Shrinkage of cell cytoplasm as water moves out of cell by osmosis

Extreme Halophiles

Require high salt concentration (up to 30%)

Facultative Halophiles

Tolerate salt concentrations (2-10%)

Chemoheterotrophs

Use organic molecules as both carbon and energy source

Autotrophs carbon source

CO2

Nitrogen Requirements

-Component of proteins, DNA, ATP

-Most bacteria decompose protein-containing material for N source

Sulfur Requirements

-Used in amino acids, thiamine, biotin

-Most bacteria decompose proteins for S

Phosphorus Requirements

-Used in DNA, RNA, ATP

-Found in membranes (phospholipids)

Trace elements

Inorganic elements required in small amounts

-Used by cells as enzyme cofactors

Obligate aerobes

Require O2

Facultative anaerobes

Able to grow w/ or w/o O2

-Grow via fermentation or anaerobic respiration when O2 not available

Anaerobes

Unable to use O2, most harmed by it

Aerotolerant anaerobes

Tolerate but cannot use O2

Microaerophiles

Require O2 concentration lower than air

Organic growth factors

Organic compounds from environment

-Vitamins, amino acids, purines, pyrimidines

Chemically Defined Media

Exact chemical comp. is known

Fastidious organisms

Require many growth factors provided in their growth media

Complex media

Extracts and digests of yeast, meat, or plants; chemical composition varies batch to batch

-Nutrient broth, agar

Reducing media

Used for cultivation of anaerobic bacteria, contain chemicals that combine with O2 to deplete it

Capnophiles

Require higher CO2 for growth

Differential media

Allow distinguishing of colonies of different microbes on the same plate

Selective Media

Suppress unwanted microbes, contain inhibitors

Enrichment culture

Encourages the growth of a desired microbe by increasing very small numbers of a desired organism to detectable levels

Pure cultures

Only one species or strain

-Often called a colony-forming unit (CFU)

-Streak plate method to isolate pure cultures

Bacterial division

Bacterial growth is represented by an increase in number of cells, not size

Generation time

Time required for a cell to divide (20min-24hr)

Lag phase

-No/little increase in number

-Intense metabolic activity for rapid growth

Log phase

-Rapid reproduction

-Exponential growth

Stationary phase

-Growth slows as carrying capacity is approached

-Cell death balances number of new cells

Death phase

Deaths exceed production of new cells

Plate counts

-Count colonies on plate that have 30-300 CFUs

-Serial dilution to ensure right # of colonies

Filtration

Solution passed through filter that collects bacteria

Direct microscope count

-Volume of bacterial suspension placed on slide

-Average number of bacteria per viewing field is calculated

-Number of bacteria/ml = # of cells / volume of area counted

Turbidity

Measurement of cloudiness w/ spectrophotometer

Metabolic activity

Amount of metabolic product is proportional to number of bacteria

Dry weight

Bacteria are filtered, dried, weighed; used for filamentous organisms