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44 Cards in this Set

  • Front
  • Back
Microbial growth
increase in number of cells, not cell size
culture
To grow or a population of bacterial cells
Three Physical requirements for Microbial growth
temperature
pH
osmotic pressure
five categories based on temperature range of growth
Each bacterium within a category has a Minimum temperature of growth, Optimum temperature of growth and a Maximum temperature of growth
MESOPHILES
Pathogenic bacteria
Optimal : 37ºC (98.6ºF)
ex:
Escherichia coli
Streptococcus
pneumoniae
Danger zone
Cold foods minimum 40ºF (5ºC)
Hot foods minimum 140ºF (60ºC)
pH (most bacteria)
Most bacteria grow between pH 6.8 and 7.2
Acidophiles
grow in acidic environments
ex: Lactobacillus, Streptococcus
Molds and yeasts (pH)
grow between pH 5 and 6
Rhizopus
Aspergillus
Penicillium
Saccharomycetes
Osmotic Pressure
Hypertonic environments, increase salt or sugar, cause plasmolysis
(cheese, ham, jelly, jam, fruit preserves)
obligate halophiles
require high osmotic pressure or die - Great Salt Lake (30%)
facultative halophiles
tolerate high (salt or sugar) osmotic pressure but don't require it.
Macro elements:
carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus
Trace elements (cofactors)
Inorganic elements required in small amounts usually as enzyme
ex:
magnesium, zinc, colbolt
Oxygen Gas:
O2 electron acceptor for aerobic growth

anaerobic growth requires H2, Fe, S as electron acceptor
Organic growth factors:
metabolically deficient organism
organic compounds cannot synthesize (vitamins, amino acids, purines, pyrimidines)
obtained from the medium
fastidious
microbes that require organic growth factors
Hydrogen
Structural function in organic molecule and energy source
Source is any organic molecule (ex: glucose)

H is energy source for chemosynthetic bacteria
(Sunlight is energy source for photosynthetic bacteria)
Oxygen
Structural function in organic molecule
Source is any organic molecule
Nitrogen
Structural function in amino acids, proteins
Most bacteria decompose proteins as source of N
Sulfur
Structural function in amino acids: ex: methionine
Most bacteria decompose proteins as source
Some bacteria use SO42 or H2S (inorganic)
Phoshorus
Structural function in DNA, RNA, ATP, and membranes
PO43 is a source of phosphorus
obligate aerobes
Require Oxygen
aerobic
Facultative anaerobes
aerobic
and
anaerobic
Obligate anaerobes
anaerobic
Killed by Oxygen
Aerotolerant anaerobes
anaerobic
Not
killed by Oxygen
but it doesn't grow
Microaerophiles
Little air lovers (15% Oxygen)
Chemically Defined Media:
exact chemical composition is known
qualitative, quantitative
Complex Media
qualitative but not quantitative
extracts and digests of yeasts, meat, or plants
Nutrient broth
Nutrient agar
Culture Medium
Nutrients prepared for microbial growth (i.e. nutrient broth, mannitol salts)
Sterile:
no living microbes
Inoculum:
Introduction of microbes into medium
Culture:
Microbes growing in/on culture medium
Agar:
Complex polysaccharide
Used as solidifying agent for culture media in Petri plates, slants, and deeps
Generally not metabolized by microbes
Liquefies at 100°C
Solidifies ~40°C
Anaerobic Culture Methods
Use reducing media
contain chemicals that combine O2
(thioglycollate or oxyrase)

plus

grow in Anaerobic jar
Capnophiles
require high CO2

CO2-packet


Neisseria gonorrhoeae is a capnophile
Selective Media
suppress unwanted microbes and encourage desired microbes
Differential Media :
visual distinction between types of microorganisms
Mannitol Salts
Selective:
high salt concentration selects for growth of Staphylococcus
Mannitol Salts
Differential:
differentiates between pathogenic and non pathogenic yellow pathogenic; red non pathogenic
Differential:
Differentiates between
Escherichia coli ferments lactose (pink)
Salmonella (non fermenter appears colorless)
pure culture
A contains only one species or strain
Binary fission:
asexual process
Phases of growth