Microbial Growth Flashcards
Physical requirements for growth
pH
Temperature
Osmotic Pressure
Chemical requirements for growth
Carbon
Nitrogen
Sulfur
Phosphorus
Oxygen
Trace elements
Organic growth factors
3 primary groups for temperature
Psychrophiles (cold dudes)
Mesophiles (normal dudes)
Thermophiles (hot dudes … pause)
Pyschotrophs
Grow at 0 degrees celsius
Optimum temp 20-30
Can’t grow past 40
Food spoilage of refrigerated foods
Mesophiles
Optimum of 25-40
Very similar temp to us as humans (our body temp)
Live in animals
Most common spoilages and disease organisms
Thermophiles
Optimum 50-60
Hyperthermophiles >80
What pH do bacteria grow best in?
Between 6.5 and 7.5
What do you use to neutralize and maintain proper pH?
Buffers
What causes plasmylosis?
high osmotic pressure
What is phosphorus used for?
DNA
RNA
ATP
Trace elements facts
Usually as enzyme cofactors
Inorganic elements required in small amounts
Iron
Copper
Zinc
Molybdenum
Microbes that require oxygen to live are called?
obligate aerobes
True or false: Obligate aerobes are at a disadvantage and if so why?
TRUE
Oxygen is poorly soluble in water of their own environment
Facultative anaerobns are?
Ability to continue growing withount oxygen
Genus: Clostridium
Half of dry weight of a typical bacteria cell is?
Carbon
Chemoheterotrophs get most of their carbon from?
The source of their energyW
What’s sulfur used for ?
Amino Acids
Thiamine
Biotin
Most bacteria decompose protein for the sulfur source
What are the enzymes that help deal with toxic forms of oxygen produced during cellular respiration?
Superoxide dismutase
Catalase
Peroxidase
Aerotolerant Anaerobes are?
Fermentative
CANNOT use oxygen for growth
Tolerates oxygen
Contain superoxide dismutase
Microaerophiles
Are aerobic
Require oxygen
Only grow in oxygen concentrations lower than those in air
Are sensitive to superoxide radicals and peroxides
Where are biofilms found?
Digestive system
Sewage treatment systems
Can clog pipes
Biofilms are involved in __ infections (percentage)
70%
How do bacteria in biofilms communicate?
Quorum sensing
Culture media definition
Nutrients prepared for microbial growth
Sterile means?
No living microbes
Innoculum definition
Introducing microbes into medium
What is a culture?
Microbes growing in or on a culture medium
What is agar used as?
Solidifying agent for culture media in petri dishes
slants
deeps
Agar is not __ by microbes
Metabolized
Agar liquifies at __ and solidifies at__
100 celsius
40 celsius
What are the types of culture media?
Chemically defined
Complex media
Chemically defined media is?
Exact chemical composition is known
Complex media is?
Extracts of meat, yeast, or plants
chemical composition varies bach to bach
Types of complex medias?
Nutrient broth
Nutrient agat
In complex media; the energy, carbon, nitrogen, and sulfur requirements of the microorganism are provided by ___?
Protein
Partial digestion does what?
Acids or enzymes reduce proteins to peptones (shorter chain amino acids)
What is reducing media used for?
Cultivation of anaerobic bacteriaW
What chemical does reducing media have and what does it do?
Sodium thioglycate
This combines with O2 and depletes it
What is selective media used for?
Used to see one particular microorganism
Differential media is to for?
Distinguishing colonies of a specific microorganism
True or false: Differential and selective medias can be combines
TRUE
Mannitol Salt agar
Used to select for halophiles
What’s an enrichment culture?
Provides nutrients and environmental conditions that favor a particular microbe
What is a pure culture?
Contains only one species or strain
What is a colony?
Population of cells arising from a single cell or spore
AKA colony forming unit
What method is used to isolate pure cultures?
Streak plate method
How do bacteria grow? (increase in number)
Binary fission
Binary fission steps
Cell elongates and dna is replicated
Cell wall and plasma membrane constrict
Cross wall froms seperating the DNA
Cells seperatw
What is the generation time?
When number of cells in each generation is expressed as a power of 2, the exponent tells the number of generations (doublings) that have occured
Time required for cell to divide
4 basic phases of growth
Lag
Log
Stationary
Death Phase
Lag phase
Intense activity but no increase in population
Log phase
Increase in population
Stationary phase
Period of equilibrium
Death phase
Population is decreasing
What’s an advantage of using the plate count method?
It measures the number of viable cellsW
Most common used
What’s a disadvantage of plate count method?
It takes time , usually 24 hours
What do platecounts assume?
Assume that each live bacterium grows and divides to produce a single colony
However, this is not always true
What can cause innacuracy in plate count?
Too many colonies present and cells overcrowd and don’t develop
What is the golden rule
FDA: 24-250
Scientists: 30-300
Serial dilution does what?
Dilutes the original inoculum several times to ensure colony is in golden rule range
When is most probable number method useful?
When microbes won’t grow on solid medium
When growth of bacteria in liquid differential medium is used to id microbes
