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112 terms

Nutrition, Growth, and Control of Microbes

Diane Mauldin, Biology 260, Exam 3
nutritional requirements for growth
A. A source of energy.
B. A source of carbon (CO2 or organic molecules)
C. A source of nitrogen via nitrate salts for amino acids, purines, and pyrimidines.
D. A source of sulfur for some amino acids and some coenzymes.
E. Vitamins for coenzymes
F. A source of phosphorous (phosphates) for ATP and nucleic acids.
G. Minerals:
1. Na+, Ca++, etc.
2. Include trace element metals for cofactors (zinc, Cu, etc).
H. Water (keeps molecules in solution, hydrolysis)
Nutritional Types
1. Autotroph
2. heterotroph
3. phototroph
4. chemotroph
acquires its carbon from carbon dioxide
acquires its carbon from an organic source
acquires its energy from light
acquires its energy from organic or inorganic molecules
photosynthetic organisms i.e., plants, algae, some bacteria and protozoa
photosynthetic bacteria that use organic acids as a carbon source
animals, most protozoa, most bacteria, and fungi
possibly the most numerous organisms on the planet, archaea
temperature range
where the microbe can grow
temperature optimum
where the microbe grows best (near the top of a microbes range)
0 to 20, refrigerator spoilage and plant diseases
10 to 47, human disease causing microbes
a mesophile that can grow at 0, disease and spoilage
45 to 80, few human disease, compost piles
over 80, includes extremophiles (also under 0)
extreme temperature affects:
bacterial enzymes and structural proteins (archaea have the proteins that can survive these extremes)
generate ATP
1) fermentation
2) anaerobic respiration
3) aerobic respiration
4) oxygenic photosynthesis
5) anoxygenic photosynthesis
6) archaea photosynthesis
does not generate ATP
does sugar synthesis
1) oxygenic photosynthesis
2)anoxygenic photosynthesis
3) chemosynthesis
ATP --> synthesis --> growth & reproduction
-DNA/RNA (nucleoside triphosphate)
bordatella pertussis: reproduction
binary fission
bordatella pertussis: metabolism
bordatella pertussis: carbohydrate source
bordatella pertussis: energy source
psychrophile optimum
mesophile optimum
psychotolerant optimum
20 to 40, but can grow at as low as 0
requirements for growth & reproduction
1) adequate nutrition
2) optimum temperature
3) optimum leveles of O2 (or no O2) media
4) optimum pH
5) optimum osmolarity
O2 requirements reflect metabolic pathways and enzymes such as:
1) fermentation vs cellular respiration
2) ability to produce catalase and superoxide dismutase
obligate aerobes
O2 must be present
can tolerate a small amount of O2
facultative anaerobes
can live with or without O2
pasteur point
oxygen level at which an organism switches from aerobic to anaerobic metabolism
obligate anaerobes
cannot live in the presence of O2 - no superoxide dismutase or catalase
optimum pH 7
optimum pH 3
optimum pH 12
osmotic effects: high solute concentrations in a cells environment result in:
cellular dehydration and plasmolysis with protein precipitation
osmotic effects: low solute concentrations in a cells environment result in:
water entering the cell such that cells may lyse
require an environment with a high concentration of sugar
require an environment with a high salt concentration to stabilize their membranes
osmophiles and halophiles:
1) don't dehydrate because they concentrate compatible solutes that don't interfere with their metabolis, e.g. K+ and amino acids
2) some have water binding proteins
media types
1) synthetic
2) nonsynthetic
3) enriched
4) selective
5) differential
6) liquid
7) solid
chemically defined
nonsynthetic (complex)
infusions and extracts ("rich"), e.g. nutrient broth and nutrient agar we use in class
additves are included to promote growth of fastidious bacteria, e.g. TSA and blood agar
prevents the growth of one type of bacteria without inhibiting the growth of another type, e.g. EMB, Columbia CNA, SM 110, and mannitol salt agars
SM 110
only one that is only selective
EMB and Hektoen
selective against G+
Columbia CNA
selective against G-
only one that is only differential
the way an organism grows on or its effect on a media helps tell the bacteria apart, e.g. EMB, blood and ChromAgar, MsA, Columbia CNA
good for propagating large numbers of organisms as well as for testing
shows surface growth patters; convenient for "pure culturing" organisms
generation time
the time it takes to double the number of viable cells
growth of unicellular organisms
= more individuals via mitosis or binary fission
= a larger population of cells
= reproduction
population growth rate
dependent on the population's generation time
lag phase
1) cell growth, increase in cell mass
2) varies depending upon the condition and nature of the initial cells
a)dormant vs dividing cells
b)slow dividers vs fast dividers
c)the transition to the log phase is sensitive to temperature, osmotic pressure, etc.
log phase: cells are dividing at a rapid and constant rate (exponential or logarithmic)
1)the rate related to environment conditions (i.e. optimum vs sob-optimum
2)proportional to the rate of energy metabolism
3) microbes are particularly susceptible to antibiotics and other chemical agents at this time
log phase: duration
1) related to cell density, "biological space", or M concentration
2) the accumulation of toxic products and the exhaustion of nutrients terminates this phase
3) related to genetics of the organism, i.e. aerobic organisms produce fewer toxic wastes
stationary phase
1) there is a balance between divisions and death; no increase in the number of viable cells
2) cells begin to produce defensive proteins and go into survival mode
3) the length of this phase varies with the kinds of wastes and the temperature
4) the cells most sensitive to the changing conditions die first
death phase
1) bacteria are dying exponentially
2) the death curve doesn't drop to zero due to the presence of resistant individuals and/or endospores
3) organisms are no prepared for growth; there is a long lag phase if microbes are transferred to a fresh medium
phases of bacterial population growth
1) lag phase
2) log phase
3)stationary phase
4) death phase
equal concentrations of a substance found inside of cell and outside of cell
Most convenient technique for measuring bacterial growth
turbidity, but also includes dead cells, even "clear" cultures may have millions of cells
most sensitive technique for measuring bacterial growth
plate count
viable plate count, serial dilution
continuously dilute bacterial through different vials until the petri plate has a reasonable amount of colonies to count.
Multiply number of colonies counted by dilution to give total number of bacteria in substance.
bacterial population size equation
population size = a x 2n
a = the number of cells with which you start
n = number of generations
inhibit bacteria
- bacteriastatic
5)sporicide (destroys bacterial or fungal spores)
dry heat
sterilizes -----> incerate, dry oven
moist heat
-autoclave (pressure cook)
sterilizes if spores are no present
autoclave (pressure cooker)
results in temperatures above boiling, good penetration, the most practical and dependable
1) does not sterilize
2) used to eliminate pathogens from food products (usually beverages)
3) controlled heat below boiling, e.g. 72C for 15 seconds
4) media that are concentrated or contain fats and sweeteners (skim milk vs cream) require higher temperatures
pasteurization created because of
TB found in animals which could spread to humans. Also rids of E.Coli and Listeriosis.
does pasteurization sterilize?
Does tyndallization sterilize?
to reduce the number of microbes
reduce the number of pathogens off of inanimate surfaces
reduce or inhibit microbes on living tissue
to eliminate microbes
remove or kill all microbes (incapable of reproducing)
you sterilize plus remove microbial toxins
thermal death point (TDP)
lowest temperature at which microbes are killed in 10 minutes
thermal death time (TDT)
shortest time it takes to kill all microbes at a given temperature
dilution tests
1)bacteria are added to tubes with different dilutions of a chemical agent and then incubated
2) this method is used to identify agents that prevent growth at the greatest dilution.
minimal inhibitory concentrations (MIC)
the tube with the lowest amount of agent that is without visible growth (turbidity method)
minimum bactericidal concentration (MBC)
the tube with lowest amount of agent that is without any growth.
-start with tube after MIC, spread out on petri dish until no bacteria is left
Microbe most likely resistant to that antibiotic has an MIC of
over 1, want lowest MIC antibiotic you can find.
three prokarya molecules recognized by toll-like receptors
1) peptidoglycan
2) lipopolysaccharide
3) flagellin
4) porin protein
production of beta-lactamase makes bacteria resistant to what family of antibiotics?
identify the tenericute that attacks mucous membranes and the synovial membranes of the joints.
explain the difference between lateral gene transfer and vertical gene transfer.
lateral gene transfer transfers genes to a neighboring cell.
vertical gene transfer transfers genes to daughter cells
When preparing a smear for this stain, you expect to heat-fix it.
positive stain
Enzymes speed chemical reactions by
decreasing the activation energy required for a reaction
In the context of genetic engineering, the term vector refers to
the DNA into which a gene is spliced
CO2, H2, and CH4 can be generated by this metabolic process.
CO2 is always generated by this metabolic process.
aerobic cellular respiration and anaerobic cellular respiration
Paul Ehrlich
-Made the first systematic attempt to find a selective agent to treat disease.
-Found methylene blue, injected into a rabbits ear, stained only neuron endings. It was selective, he want to find more like it for humans.
Ehrlich: dyes & arsenic compounds used in dyes
-trypan red 500 sometimes in mice
-atoxyl 591 (arsenic red)
-salvarsan 606
trypan red 500
killed trypanosomnes sometimes in mice
atoxyl 591
(arsenic red) killed trypanosomes, made mice dance
salvarsan 606
(salvation + arsenic, derived from atoxyl)
-killed trypanosomnes in mice and horses, no side effects
-read that spirochetes were cousins to trypanosomes (but they are not)
-cured rabbits of syphilis (but only humans can get it)
-cured thousands of people of syphilis but also killed occasional person
-first "blockbuster" drug, most widely prescribed in world at a time
-may have caused initial spread of HIV because of sharing needles
sensitivity disks (filter paper method)
-look for clear area around paper disks soaked in a given agent - where bacterial growth has been inhibited (inhibition zone)
1)the media used in determining sensitivity should be comparable to tissue fluids of th body
2) staph a is the usual test organism
3) can't tell if the organisms are dead or inhibited
4)various agents diffuse through agar at different rates
death curves
counts of viable bacteria made at intervals
gerhard domagk
1) produced the first sulfa drug
2) the dye prtonsil converts to sulfanilamide once introduced intro the patient
3) sulfa drugs were the first effective broad specturm selective agents
targets of antibiotics
-cell well - bacitracin
cell memberane - polymyxins
-dna/rna - nadaladaxic acid, ciproflaxin?
-ribosome -erythromycin, tetracycline
metabolic products
characteristics of anitbiotics
1) usually selective
2) produced y bacteria and molds
3) target bacteria
4) broad spectrum
5) low toxicity index
6) high therapeutic index
antibiotics at low concentrations (most common in nature
-communication molecules, inducer
1)stimulate biofilm production
2) gene expression
-may be metabolic intermediates and nutrient molecules