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BIO205 - Ch 6 - Microbial Growth - RioSalado - AZ

Groups of cells large enough to see without microscope. Colonies - hundreds of thousands of cells
2 main requirements for microbial growth. Physical (temp, pH, osmotic pressure), & chemical (carbon, nitrogen, oxygen, phosphorus, etc.)
3 temperature classifications of microbes. (1) psychrophiles (cold-loving), (2) mesophiles (moderate-temp-loving), & (3) thermophiles (heat-loving).
Why is it difficult to define psychrophile, mesophile, & thermophile? Because their ranges & max. growth temps that define them "are not rigidly defined."
Which group of bacteria grow well in refrigerator temperature? Psychrotrophs - "moderate or faculative".
Many thermophilic bacteria cannot grow below __ degree Celsius. 45
Extreme hyperthermophiles have optimum growth temp. of __ degree Celsius. 80+
Acidophiles can tolerate? acidity - low pH of 1 even
Optimum pH of molds & yeast 5-6 pH
Osmotic loss of water causes __. plasmolysis
Obligate/extreme halophiles high salt concentrations - lovers
Chemoautotrops & photoautotrops get carbon how? from CO2
Besides carbon, DNA & RNA synthesis require? nitrogen & phosphorus
Half the dry weight of bacterial cell is? carbon
Organisms use nitrogen primarily to form __. amino group of the amino acids of proteins.
Name 3 foods preserved by high osmotic pressure. salted fish, honey, sweetened condensed milk
nitrogen fixation Using gaseous nitrogen directly from atmosphere (N2)
How is sulfur used? to synthesize sulfer - containing amino acids & vitamins like thiamine & biotin
phosphorus is essential for? Synthesis of nucleic acids & phospholipids of cell membrane, & ATP
Potassium, magnesium, & calcium used as __. cofactors for enzymes
Name some trace elements iron, copper, molybdenum, & zinc - usually cofactors
Which bacteria are primary producers at ocean floor? chemoautotrophs
Organisms that require oxygen to live. obligate aerobes
Faculative anaerobes use what? Oxygen when available but cause use fermentation to continue growth - like E. coli
Bacteria unable to use molecular oxygen Obligate anaerobes - like tetanus & botulism
SOD - super oxide dismutase an enzyme that destroys super oxide (O2) free radicals.
Super oxide free radical A toxic form of oxygen (O2-) formed during aerobic respiration.
Singlet oxygen Highly reactive molecular oxygen (CO2-)
Which bacteria lack SOD? Obligate anaerobes - lack this enzyme to nutralize oxygen.
peroxide anion O2^2- - toxic - part of hydrogen peroxide & benzoyl peroxide - catalase nutralizes.
peroxidase breaks down hydrogen peroxide
hydroxyl radical (OH) Most reactive oxygen form - produced in aerobic respiration
Microaerophiles Aerobic bacteria that grow only in low oxygen concentrations.
Organic growth factors Essential organic compounds an organism cannot synthesize on own & must obtain from environment. Ex - humans needing vitamins.
Culture medium Nutrient material prepared fro growth of microorganism in lab.
Inoculum Microbes introduced to culture medium to initiate growth.
culture microbes that grow & multiply in or on a culture medium.
agar solidifying agent made of a complex polysaccharide derived from marine alga - thickens jellies & ice cream - hard for bacteria to degrade.
Chemically defined medium culture medium with exactly known chemical composition
complex media culture medium with varying chemical composition.
nutrient broth complex medium in liquid form
nutrient agar complex medium in solid form
reducing media Culture medium that removes dissolved oxygen to allow anaerobes to grow - special anaerobic jars, etc. are used.
oxyrase respiratory enzyme used to remove oxygen from petri plates.
High CO2 levels are obtained with __ jars. candle - lighted candle consumes oxygen.
capnophiles microbes that grow better at high CO2 concentrations
selective media suppress growth of unwanted bacteria & encourage growth of desired microbes.
defferential media Solid culture medium used to distinguish colonies of the desired organism grown on same plate as others - Ex: blood agar
Enrichment culture Liquid medium that provides nutrients & environmental conditions favorable to growing specific microbe - selective & used to increase sm. populations.
streak plate method is used to obtain? isloated (pure) culture
lypophilization Freeze-drying - water removed
generation time tme required to double its population
What scale is used to graph bacterial growth? Logarithmic scales
Bacterial growth curves show? Growth of cells over time - lag, log, stationary, & death phase.
What occurs during lag phase of growth? Intense metabolic activity to synthesize reproductive enzymes & molecules.
What occurs during log phase of growth? Period of exponential growth - most active reproductive pahse - most active metabolically - most sensitive to adverse environmental conditions.
What occurs during stationary phase of growth? Growth rate matches death & population stabolizes - metabolic activity slows - equilibrium.
What occurs during death phase of growth? More death than reproduction.
Which phase does radiation & antimicrobial drugs interfere with? Log phase
Population numbers are usually recorded as? cells per milliliter of liquid; or gram of solid material
Most frequently used measuring method of bacterial populations. Plate count - advantage is that it measures number of viable cells, but disadvantage is it takes time.
Colony-forming units (CFUs) Plate counts - colony that results from a chain or bacterial clump instead of just one bacteria.
Serial dilutions Process of diluting a sample several times to make it easier to count.
Pour plate method Method of mixing bacteria into a solid nutrient medium by melting the medium & pouring it into a Petri dish to solidfy.
Drawbacks of pour plate method? Damages heat-senitive microorganisms.
Spread plate method Bacteria added to surface of solid agar medium & spread over the surface with a glass rod.
Why is spread plate method better than pour plate? Bacteria aren't exposed to heat needed to melt medium.
Most probable number (MPN) method Statistical estimation stating that the more bacteria there are, the more dilution needed to produce a zero count.
turbidity How cloudy the medium becomes w/cells - measured by a spectrophotometer - light absorbed by cells.
Created by: Ladystorm
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