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64 Cards in this Set
- Front
- Back
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bacterium that has an absolute requirement of oxygen for growth |
aerobe/strict aerobe |
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microbes that grow optimally at a pH below 5.5 |
Acidophiles; neutrophiles sorta |
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Non-culturable bacteria |
most can't be grown in the lab so we know little about them .1 or less in open ocean form colonies |
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why can't most be grown in lab? |
hard to be isolated
-don't know favorable isolation temp, pH, pressure, |
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how can we characterize unculturable organisms? |
genome sequencing dna from unculturable can be amplified and sequenced |
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genome sequencing |
1. extra total DNA from environmental sample 2. amplify 16 S rRNA genes using PCR 3. separate the amplified DNA molecules 4. analyze DNA sequences to determine species in sample |
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non-culturalbe bacteria |
direct sequencing(with or w/o cloning) extraction of DNA from environment sample followed by PCR(for SSU rRNA genes) and sequencing -compared to databases of known sequences for identification |
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FISH |
fluorescence in situ hybridization: use fluorescently-labeled DNA probes which will hybridize to the DNA in cells;allows the identification of certain species or genera in a bacterial sample(often probes to 16S rRNA genes are used) 1. fix cells in place and permeabilize 2. add fluorescent probes then wash 3. view via epifluorescence microscope 1 dna probe of 16srRNA gene sequence specific to 1 other DNA probe of 16S rRNA gene specific to species 2 |
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fluorescent antibody probe |
use antibodies to recognize proteins that are specific to a group of bacteria |
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special aspects: endospores |
-a resting form -cell differentiation -resistant to heat, drying, acid, bases, disinfectants, and some radiation -shut down metabolism completely, and compact chromosomal DNA tightly with protective proteins -can be dormant for long time(1000's of years) |
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why endospores? |
for survival, not dispersal of progeny(stress resistant endospores) |
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when |
1 bacterial cell can produce 1 endospore when nutrients are scarce |
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bacillus |
aerobe and facultative -most studied -pathogenic species eg. anthrax |
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clostridium |
anaerobe -pathogenic species -tetanus, botulism -gas gangrene |
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thermoactinomyces |
-aerobes -close to bacillus -thermophilic |
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sporolactobacillus |
-endospore forming lactic acid bacteria |
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sporotomaculum |
-carry out anaerobic resp, using SO4 as terminal e- acceptor |
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sporohalobacter |
-anaerobic, salt-resistant bacteria from dead sea |
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biofilm |
microcolonies of bacterial cells attached to a surface by means of adhesive polysaccharides excreted by the cells -groups/layers of microbes on a surface that interact with and support each other |
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steps in formation of biofilm |
Steps in biofilm formation include: (1) loose attachment to the surface, (2) a stable attachment via formation of microcolonies (3) secretion of a polysaccharide matrix that encases the bacteria and formsa complex architecture. (EPS) (4) Secondary colonizers then join the biofilm.Biofilms can grow or disperse, depending on environmental conditions |
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biofilm medical important |
cause dental cavities(step mutans) form biofilms in teeth -Pseudomonas aeruginosa form in lungs of cystic fibrosis -pathogens are a problem on catheters, IV's, and hospital tubing-hard to remove |
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primary infection |
subvenous cathetr artifical hip mouth |
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secondary catheter infection |
brain kidneys intervertebral spaces hip |
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quorum sensing |
bacteria can "communicate" with other bacteria via secreted molecules called "autoinducers" |
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gene X and quorum |
- gene X depends on density of culture -gene X can also be used as means of communciation b/w microbes |
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autoinducer and quorum sensing |
-release the autoinducer into environment as population density increases -changes in autoinducer levels causes regulation of gene expression |
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low density and AI |
low cell density=AI diffuse away from cell |
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high density and AI |
more ai are present -bind to receptors that regulate TXN of genes -genes responsible for AI production are expressed, positive feedback loop results |
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mechanisms controlled in quorum sensing |
motility conjugation biofilm formation pathogenesis (cholera toxin formation) |
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quorum sensing photo |
toxins, enzymes, and surfactants |
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vibrio |
AI: homoserine lactone physiology: bioluminescence |
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psuedomonas |
AI-homoserine lactone FX-pathogenesis |
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agrobacterium |
AI-homoserine lactone fx-conjugation |
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bacillus |
ai-peptide fx-competence, development |
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enterococcus |
ai-peptide fx-conjugation, plasmid maitenance, pathogenesis |
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myxococcus |
ai-peptide fx-development |
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streptococcus |
ai-peptide fx-transduction |
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staph |
ai-peptide fx-pathogenesis |
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vibro ex |
v. fischer secretes AI over> AI molecule that can diffuse into and out of cell 3. high ai>ai binds to luxR>activate LUXR>eXp lux operon>encode gene for luciferase>enzyme for light |
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quorum sensing low population density |
low level TXN from operon. low [AHL] is in cell. AHL and LUXR don't interact. Lux R does not bind lux box for activation. light is not produced |
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high ahl in cell |
AHL and lux R interact 2. lucR binds lux box 3. light=produced |
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1. how to inhibit bacterial growth or eliminate |
1. filtration 2. temperature(autoclave), heat, freeze 3. radiation( thymine dimer via 260-280 nm) 4. chemical methods(desinfectants, antiseptics) |
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2. temp used to eliminate |
1. heat denatures protein and nucleic acid. 100 kills microbes real quick 2. autoclave-adds pressure, keeps fluid from evaporating during high temp 3. damage cells by ice crystals/stop biochem reactions |
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+ and - of filtration |
+ separate/isolate bacteria -may lose small bacterial that want to isolate by bacterial falling through filters |
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filtration |
purify liquids -newer use nylon/teflon with pore .2 or .45 (msall to keep out most bacterial and eukaryal cells) -viruses by ultra(reduce size 10 to 100nm) |
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autoclave |
adds pressure(keep fluid from evaporating during high temp) |
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freezing |
damage cells via ice crystals -stop biochem reactions |
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radiation |
UV 260-280 nm damage DNA forming thymine dimers |
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chemical method |
kill microbe/inhibit growth |
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desinfectants |
on non-live to kill infectios microbes |
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antiseptic |
-living tissue to kill infectious |
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ethanol |
lab |
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triclosan |
soap, deodorant, cosmetic |
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oxidizing Na hypo |
swimming pools, hot tubs, stop microbes |
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benzalkonium chloride |
lysol |
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glutaraldehyde |
prep bio specimens |
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quorum sensing is mediated by |
- genetic info transfer |
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Once the autoinducer excreted by Vibrio fischeri reaches a critical concentration, it is ableto diffuse back into the cell. What is its next action? |
c) Bind to a transcriptional activator protein to activate transcription of the lux genes |
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Which one of the following is NOT a physical factor that affects the growth rate of cells? |
a) nutrient concentration |
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Which is the best definition of an antiseptic? |
b) A chemical agent that is applied to living tissue to kill and inhibit microbes |
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growth curve predictions:lag |
# cells in inoculum age cells in inoculum anything that affects metabolic (temp, pH, rich vs. minimal, type) |
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log |
any affect metabolic |
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stationary |
-amt of limiting(one that runs out first) |
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growth curve at minimal media |
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