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.
1. Na+, Ca++, etc.
2. Include trace element metals for cofactors (zinc, Cu, etc).
H. Water (keeps molecules in solution, hydrolysis)
extreme temperature affects:
bacterial enzymes and structural proteins (archaea have the proteins that can survive these extremes)
2) anaerobic respiration
3) aerobic respiration
4) oxygenic photosynthesis
5) anoxygenic photosynthesis
6) archaea photosynthesis
ATP --> synthesis --> growth & reproduction
-DNA/RNA (nucleoside triphosphate)
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
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
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
infusions and extracts ("rich"), e.g. nutrient broth and nutrient agar we use in class
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
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
growth of unicellular organisms
= more individuals via mitosis or binary fission
= a larger population of cells
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
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
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
Most convenient technique for measuring bacterial growth
turbidity, but also includes dead cells, even "clear" cultures may have millions of cells
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
5)sporicide (destroys bacterial or fungal spores)
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.
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
4) porin protein
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
In the context of genetic engineering, the term vector refers to
the DNA into which a gene is spliced
CO2 is always generated by this metabolic process.
aerobic cellular respiration and anaerobic cellular respiration
-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)
(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
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
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