Bacterial Phys I And Ii, Normal Flora

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gives a quantitative idea about the presence of microorganisms such as bacteria, yeast and mold in a sample.Represents number of colony forming units

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Total Viable Count (way to measure cell number)

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cloudiness or haziness of a fluid caused by individual particles (suspended solids)

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turbidity

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4 distinct phases in bacteria growth

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1: Lag Phase
2: Exponential (log) phase
3: Stationary phase
4: Death phase

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What occurs during the lag phase?

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Adaptation to new medium

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What occurs during the exponential (log) phase?

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Balanced increase in all cell constituents with logarithmic increase in cell population. growth rate or generation time differs by organism, nature of medium, environmental factors

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What occurs during stationary phase?

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Results from nutrient limitation, accumulation of toxic products, pH change, reduced oxygen tension

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Slow generation times are associated with what?

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Chronic infections (like tuberculosis)

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Fast generation times are associated with what?

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Enteric bacteria, acute infections

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Equations for exponential growth?

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Nt = # cells at t = N0 x 2ⁿ
log Nt = log N0 + nlog2
n = (log Nt - log N0) / log2

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What is generation time?

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Time it takes for a culture/population to double in number

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Generation time calculation

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t/n, where t= time, n=number of generations

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Minimum requirement for growth

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energy source, source of carbon and nitrogen, various ions

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Characteristics of photolithotrophic 0rganisms?

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energy source is light, reductant source (reducing power) is H20 (cyanobacteria) or H2S (purple sulfur bacteria); Carbon source is CO2

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Characteristics of photoorganotrophic 0rganisms?

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E: light; e- (reductant source): reduced organic cmpds; C: CO2 or organic cmpds

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Difference by lithotrophs and organotrophs?

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Organotrophs: Organic compounds are used as electron donor.
Lithotrophs: Inorganic compounds are used as electron donor.

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All pathogens are in what metabolic group?

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Chemoorganotrophs. They use organic compounds as energy source, electron source, and carbon source

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Characteristics of facultative aerobes?

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Grow in presence or absence of oxygen; aerobic growth is more efficient, but have anaerobic means of generating energy (like fermentation). Also called facultative anaerobes. E coli is example

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Micrococcus luteus is an example of what type of oxygen requirement?

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Obligate - requires O2 for metabolism

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Streptococcus pyogenes is an example of what type of oxygen requirement?

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Aerotolerant

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Definition of aerotolerant

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Can tolerate oxygen, but growth is no better. Most use fermentation exclusively

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T/F Most aerobic bacteria produce enzymes that catalyze destruction of ROS

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T

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Catalase

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Breaks down H2O2

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Peroxidase

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Breaks down H2O2

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Superoxide dismutase

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Breaks down superoxide radical

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What is a microaerophile?

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Grows best at low concentrations of oxygen, but have to have some oxygen

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Capnophile: defn

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Bacteria that require CO2 in higher amount than found in atmosphere (although all bacteria require CO2 to some extent)

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Capnophilic species have enzymes with (lower, higher) affinity for CO2

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lower - they need more CO2 than atmospheric levels

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Enzymes involved in CO2 utilization

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Pyruvate carboxylase
PEP carboxylase
Acetyl CoA carboxylase

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Mesophiles: defn

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Organizing growing best at a narrow range of temp: 30-40 degrees Celsius

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Psychrophiles: defn

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prefer low temps

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Thermophiles: defn

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prefer high temps

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How is Fe very important in host-pathogen interactions?

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Host and pathogen are always competing for it. It's necessary for electron transport processes, in cytochromes, ferredoxins, other iron-sulfur proteins

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Function of Sulfur in prokaryotes

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Cysteine, methionine, Coenzyme A

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Function of K+ in prokaryotes

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Cofactor (pyruvate kinase); principal inorganic cation in cell

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Function of Mg2+ in prokaryotes

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Cofactor for many enzymes, component of cells walls, membranes, ribosomes

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Function of Ca2+ in prokaryotes

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Exoenzymes, major component of endospores

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Organic compounds that cell must contain, but which it is unable to synthesize

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Growth factors

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T/F Growth rate of bacteria during expoential phase is constant

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T

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T/F Growth rate of bacteria during stationary phase is zero

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T

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Rate of ________ diffusion is dept upon the size of the concentration gradient between a cell's exterior and interior

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Passive

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Rate of _______ diffusion increases with concentration gradient much more rapidly and at lower concentrations of the diffusion molecule than that of passive diffusion

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Facilitated

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Why is there a saturation effect in facilitated diffusion?

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Because of carrier molecules

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What type of transporters are ATP transporters?

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ATP-binding cassette (type of active transport). Hydrolyzes ATP to move moelcules against concentration gradient

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Process by which a molecule is transported into the cell while being chemically altered

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Group translocation

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What is the PTS (phophoenolpyruvate:sugar phosphotransferase) system?

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method used by bacteria for sugar uptake where the source of energy is from phosphoenolpyruvate (PEP). The phosphoryl group on PEP is eventually transferred to the imported sugar via several proteins.

Example of group translocation

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Add diluted culture directly to top agar
Pour into petri dish and allow to solidify
Colonies form on top (black) and below
agar surface (white)

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pour plate technique

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Apply loopfull of culture to top of plate
Streak over surface of petri dish in
quadrants with loop, sterilizing

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streak plate technique

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(Substrate-level phosphorylation) : ~P is transferred to ADP to form ATP using energy derived from coupled oxidation reaction

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fermentation

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Electron acceptor in fermentation

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pyruvate or pyruvate derivative

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_____ is oxidized to _______ in fermentation

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NADH; NAD+

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theoretical yield: aerobic bacterial respiration

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38

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glycolytic pathway number ATP produced at substrate-level phosphorylation

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2

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glycolytic pathway number ATP produced at ox-phos

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6

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2 pyruvate to 2 acetyl CoA number ATP produced

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6

Front 55

Medium containing essential nutrients, in defined amounts required for growth of the organism, constituents are highly purified in/organic compounds added to distilled water. Exact composition is known.

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Synthetic or defined medium

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Employs digests of casein, beef, soybeans, or other highly nutritious (but undefined) substances

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Complex medium

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What is enrichment media?

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Addition of blood, serum or extracts to support growth of many fastidious bacteria (from CSF, sputum or wound abscesses)

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Examples of enrichment media

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Chocolate agar; Blood agar

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What is selective media?

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Additives inhibit some bacteria, enriching for others.

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Examples of selective media

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Salmonella-Shigella agar: high concentraiton of bile salts, inhibiting growth of other coliforms; can assess lactose fermentation

Bismuth sulfite agar: reduces sulfite to sulfide, results in black colonies

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What is differential media?

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Allows discrimination between groups of bacteria by visual inspection

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What is the difference in appearance between lactose and non-lactose fermenters in MacConkey stain?

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Lactose fermenters: red
Non-lactose fermenters: white

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What are the common electron acceptors in anaerobic respiration?

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CO2, sulfate, nitrate

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T/F The reductant (electron donor) may be inorganic or organic

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T

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What creates oxidant and reductant in photosynthesis?

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photochemically thru Light energy absorbed by pigments in membrane

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Two stages of glycolysis and how much ATP is produced/consumed in each

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1) Prep stage (consume 2 ATP, generate glyceral-3-P)

2) Oxidation reactions (generate 4 ATPs and 2 pyruvates)

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What 2 things can happen to pyruvate after glycolysis?

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Can be fermented or completely oxidized to CO2

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T/F many microbes are IDd on the basis of fermentation endproducts

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T

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What is chemiosmosis?

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movement of ions across a selectively permeable membrane, down their electrochemical gradient. More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration.

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Why is use of inorganic electron acceptor other than O2 less efficient than aerobic respiration?

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Because the reduction potentials are less positive

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Amphibolic pathways: defn

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Function both catabolically and anabolically

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Anapleurotic reactions: defn

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"filling up" reactions that replace intermediates for critical pathways (ex TCA)

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species that are almost always found at high numbers in a particular site; don't compromise survival of the host

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indigenous flora

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species that are usually present but in low numbers; may become indigenous if envt' changes, may vary from person to person

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supplemental flora

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organisms that at a given time may or may not be present; medically important pathogens are included in this group

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transient species

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Significance of 16S rRNA gene

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Makes up part of bacterial ribosome. Parts are very highly conserved, but other parts are very different. Allows determination of every bacterial species and ratio of species present in a sample

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T/F Bacterial 16S rRNA project resolves to Genus level

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T

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Normal healthy lactobacilli replaced by anaerobic bacteria

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bacterial vaginosis

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What are the diagnostic criteria for bacterial vaginosis?

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1. Grayish-white discharge,
2. Increased vaginal pH,
3. Positive whiff test (KOH- amine odor),
4. Presence of “Clue cells”

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epithelial cells of the vagina that get their distinctive stippled appearance by being covered with bacteria.

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Clue cells

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Community of microorganisms where microbes adhere to one another and to a solid surface and surround themselves in a protective polymeric matrix such as polysaccharide

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biofilm

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T/F The biofilm phenotype increases bacterial resistance to pH changes, oxygen, antibiotics, immune defenses, etc.

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T

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Where does the normal flora come from?

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Vaginal delivery, saliva, other normal exposures

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bacteria benefits, host is unaffected

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Commensalism

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host and bacteria benefit

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mutalism

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bacteria benefits, host is damaged

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parasitism

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What vitamins are provided by bacteria?

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biotin, pantothenic acid (B5), pyridoxine (B6), riboflavin (vitamin B complex), and vitamin K

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Protective effects of mutualistic bacteria

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1. Exclusion (bind host receptors, take up physical space)
2. Immune stimulation – antigen
priming
3. Production of bactericidal
compounds; specific (bacteriocins)
and nonspecific (metabolic
byproducts such as lactic acid and
H2O2 produced by vaginal
lactobacilli)

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T/F M cells in the colon pick up normal flora antigens, stimulation productions of IgA, thus protecting gut from pathogens like Salmonella

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T

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What are bacteriocins?

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Compounds made by one bacterial species to kill another

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Gnotobiotic: defn

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germ-free animals. Must get vitamin supplementation and live in pathogen-free envt

• Underdeveloped lymphoid tissues, low antibody titers, thin intestinal walls, low metabolism rate, highly prone to infections

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Predominate oral cavity flora

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Streptococci

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T/F The lower respiratory tract is highly colonized.

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F. The lower respiratory tract is virtually free of microorganisms.

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Bacteria living in specific niche of stomach

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Helicobacter, lactobacilli

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site of most prevalent infections of man

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oral cavity

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Many of species that inhabit ___________ are significant causes of endocarditis

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periodontal pockets in mouth

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_____ is generally acidic with high salt concentration

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skin

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Species living on skin
A) Aerobic
B) Anaerobic

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A) Surface: Staphylococci; corynebacteria
B) Sebaceous glands: propionibacterium

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Why is the small intestine a difficult environment to colonize ?

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Peristalsis and acidic pH

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Common small intestine species

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lactobacilli, enterococci

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Predominant species in large intestine

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Bacteroides, Bifidobacterium, E. coli

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T/F Urethra is generally sterile

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T

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Species of bacteria normally colonizing vagina

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Lactobacilli

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part of the normal oral flora but it erodes tooth enamel through acid production resulting in tooth decay

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streptococcus mutans

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penetrates razor-burned skin to cause folliculitis

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Staph aureus

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the leading cause of device-related infections

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Staph. epidermidis

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T/F Fecal anaerobes like E. coli can enter urethra causing UTI

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T

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after transplantation surgery patients are given immunosuppressive drugs which can lead to invasive infections with _____________

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Strep. pneumoniae

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Pneumococcal pneumonia, a secondary infection after the flu, is caused by what organism?

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Strep. pneumoniae

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antibiotic-associated pseudomembraneous colitis is caused by ____________

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Clostridium difficile

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T/F C. diff is part of normal flora but at very low numbers

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T

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What are the 6 Fs of host entry?

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1. Fomites e.g. wound contamination – Clostridium tetani
2. Flies (arthropod vectors) e.g. lyme disease – Borrelia burgdorferi
3. Feces e.g. – Cholera –Vibrio cholerae
4. Fingers e.g. Conjunctivitis – “pink eye” - Haemophilus aegypticus
5. Fornication e.g. Syphilis – Treponema pallidum
6. Food e.g. Salmonella

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Organism responsible for tetanus after nail pierces skin

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Clostridium tetani

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Causative agent of lyme disease

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Borrelia burgdorferi

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Causative agent of cholera

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Vibrio cholerae

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Causative agent of bacterial conjunctivitis

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Haemophilus aegypticus

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Causative agent of syphilis

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Treponema pallidum

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Causative agents of salmonellosis

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Salmonella typhi (worldwide); S. enteriditis (US)

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A macromolecule that binds to specific ligands or receptors on host cells and defines the tropism of the microbe for various cells or tissues. All pathogenic bacteria produce these.

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Adhesins

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Mucociliary escalator
Washing action of saliva
tears, mucus
Blood and urine flow

All of those are examples of what?

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Host defenses against bacteria adhering to cells

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Localization to a specific tissue or body site

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Tropism

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3 types of adhesins

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Pili / fimbriae
Non-pilus surface proteins
Polysaccharides

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The process through which a disease state develops

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pathogenesis

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The degree of pathogenicity produced by a pathogen (quantitative term)

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virulence

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ID50: defn

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Infectious dose. Number of organisms required to cause disease in 50% of test population

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LD50: defn

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Lethal dose. Number of organisms required to cause death in 50% of test population

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persistence of infection in non-human population of vertebrates

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enzootic

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Inanimate objects in environment of apatient or one that has been in contact with a patient, capable of sustaining the viability of an infectious agent

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Fomite