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Chapter 6
Microbial Growth
54
Microbiology
Undergraduate 2
03/05/2012

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Term
Requirements for Growth
Definition
Every organism has a range of suitable conditions it can live in; minimal, optimal, and maximum conditions.
Term
Psychrophiles
Definition
-10 - 20 degrees Celsius
Term
Psychrotrophs
Definition
0-30 degrees Celsius; grow well at refrigerator temperature = food spoilage
Term
Mesophiles
Definition
10-50 degrees Celsius; refrigeration based off principle many pathogenic microbes don't grow very well outside of the 20-40 "Danger Zone"
Term
Thermophiles
Definition
40-70 degrees Celsius
Term
Hyperthermophiles
Definition
70-110 degrees Celsius
Term
Plasmolysis
Definition
the process in plant cells where the cytoplasm pulls away from the cell wall due to the loss of water through osmosis
Term
halophiles
Definition
extremophile organisms that thrive in environments with very high concentrations of salt
Term
Important elements for survival
Definition
Nitrogen, Sulfur, Phosphorus
Term
Trace Elements
Definition
Wide variety of locations, can be toxic in high amounts ex. Fe, Cu, Zn, Mg
Term
Oxygen
Definition
Essential toxic and has toxic forms
Term
obligate aerobes
Definition
oxygen required
Term
facultative anaerobe
Definition
can grow with or without oxygen, but greater with oxygen
Term
obligate anaerobe
Definition
only grows in the absence of oxygen
Term
aerotolerant anaerobes
Definition
doesn't utilize oxygen but can grow in its' presence
Term
microaerophiles
Definition
only grows in small concentrations of oxygen
Term
SOD
Definition
superoxide dismutase detoxifies superoxide radicals/anions; converts them into oxygen (diatomic) and hydrogen peroxide
Term
Catalase
Definition
detoxifies hydrogen peroxide, converts it into water and oxygen (diatomic); our cells have catalase
Term
peroxidase
Definition
also detoxifies hydrogen peroxide, converts it into water only
Term
organic growth factors
Definition
essential organic compounds an organism is unable to synthesize
Term
biofilms
Definition
matrix made of DNA, polysaccharides, and proteins; cells communicate through film by quorum sensing. Biofilms make microbes more pathogenic, harder for drugs to penetrate film to reach cells.
Term
quorum sensing
Definition
chemical communication
Term
culture medium
Definition
nutrient material prepared for the growth of microorganisms
Term
inoculum
Definition
microbes introduced into a media to initiate growth
Term
culture
Definition
microbes that grow and multiply in or on a culture medium
Term
agar
Definition
complex polysaccharide derived from marine algae
Term
chemically defined medium
Definition
exact chemical composition is known
Term
complex media
Definition
made up of nutrients including extracts from yeasts, meat, plants, or digests
Term
Complex media (liquid form)
Definition
nutrient broth
Term
Complex media (nutrient broth + nutrient agar)
Definition
nutrient agar
Term
growing anaerobes
Definition
grown in a medium with chemicals that bind and use harmful oxygen or in a had where a candle or sack of CO2 and H2 deplete the oxygen
Term
Capnophiles
Definition
microbes that grow well in high levels of CO2
Term
Selective Media
Definition
designed to suppress the growth of unwanted bacteria and encourage the growth of desired microbes
Term
Differential Media
Definition
makes it easier to distinguish colonies of different microbes based one color changes in the media as a result of certain microbe by-products
Term
Enrichment Culture
Definition
provides nutrients and environmental conditions that favor the growth of a particular microbe but not others; like selective but focus is to increase number of desired microbes.
Term
Biosafety Levels
Definition
1-basic microbiology teaching lab
2-open bench tops, gloves, lab coats, and possible eye masks required
3-for highly infectious airborne bacterial; uses safety cabinet, and negatively air pressurized filters for the lab room
4-only a few of these lab types in the US; lab is a sealed environment, under negative pressure, HEPA filters, personal wear space suits.
Term
colony
Definition
theoretically arises from a single spore/microbe
Term
streak/plate method
Definition
isolation technique
Term
preserving bacteria: Deep Freezing
Definition
pure liquid culture is quick frozen; lasts several years
Term
preserving bacteria: Lyophilization
Definition
freeze-drying; quick frozen and then water removed with vacuum, lasts several years.
Term
Generation time
Definition
time required for a cell to divide
Term
Lag phase
Definition
little to no cell division, 1 hr to several days; time for intense metabolic activity
Term
Log phase (exponential growth phase)
Definition
cellular reproduction most productive, generation time is constant, most metabolic activity
Term
stationary phase
Definition
period of equilibrium, number of microbe deaths balanced by newly formed microbes
Term
death phase
Definition
nutrients used up/build up of by-products so number of deaths exceeds division; microbe population brought down to a sustainable size
Term
plate count (direct measurements of microbial growth)
Definition
measures the number of viable cells; assumes each bacteria is a CFU; serial dilutions are used to decrease the number of CFUs to make the counting practical.
Term
pour plate (direct measurements of microbial growth)
Definition
bacterial dilution mixed with agar before setting; can damage heat sensitive microbes and some will grow beneath surface, incubated, and CFU's counted
Term
spread plate (direct measurements of microbial growth)
Definition
bacterial dilution spread onto the agar, incubated, and CFU's counted
Term
filtration (direct measurements of microbial growth)
Definition
used to count number of bacteria in low concentration in a liquid
Term
MPN (direct measurements of microbial growth)
Definition
most probable number; is only a statement that the bacterial population falls within a certain range based of statistics; based on there number of bacteria required for growth in a medium and bacterial solution concentrations
Term
direct microscopic count (direct measurements of microbial growth)
Definition
bacterial suspension placed on microscope slide and microbes counts per volume
Term
turbidity (indirect measurement of microbial growth)
Definition
bacteria in liquid medium have light
Term
metabolic activity (indirect measurement of microbial growth)
Definition
measures amount of certain by-product to estimate amount of bacteria
Term
dry weight (indirect measurement of microbial growth)
Definition
measure desiccated microbes
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