2 - Bacterial Metabolism Flashcards
What features distinguish prokaryotes from eukaryotes?
Single, circular chromosome.
Transcription coupled to transcription.
Ribosome is 70S instead of 80S (target for antimicrobial)
Cell wall (target for antimicrobial), complex plasma membrane.
How are eukaryotic species defined? What about prokaryotic species?
Eukaryotic: sharp natural boundaries defined by ability to produce fertile offspring.
Prokaryotic: no sharp natural species boundary, defined by genetic relatedness and possession of similar physiological function.
How do we molecularly identify bacteria? What are the advantages over current classical techniques?
Through relationships in DNA composition - using amplification techniques and genome analysis and sequencing techniques.
Automation (productivity), speed, and greater accuracy.
How can PCR be used for identification?
Good to identify slow-growing or non-cultivatable bacteria such as clostridium difficile, a gram + anaerobe.
Amplifies pathogen specific DNA for rapid identification.
What technique can be used to identify whether an infection is hospital acquired (nosocomial) or not?
Analysis of restriction endonuclease patterns of the bacterial chromosome (restriction fragment length polymorphism- RFLP) using gel electrophoresis.
If RFLP of isolates are identical between patient and hospital personnel, it’s possible that the bacterium infecting pts are from that hospital worker.
What is the benefit of using analysis of unbiased next-gen DNA sequencing of the host tissue (CSF) to ID an infection?
This is when you take the hosts tissue and see if it has fragments of the bacterium within it.
Can be used to identify leptospira infection.
What is the difference between morphological and biochemical identification?
Morphology: colony morphology, cell shape, gram stain, motility, presence of capsule.
Biochemical: ability to metabolize specific substrates, produce specific end products, and antibody sensitivity.
What are two routes of metabolism after glucose is turned into pyruvate via oxidation?
Pyruvate can be respired in the presence of O2 to make CO2 and H2O (energy efficient)
In absence of O2 it can be fermented to make organic end products, little energy production, and unique to microbes (diagnostic)
What are the different types of bacterial responses to O2?
Aerobes: metabolize O2 and grow only in it’s presence.
Microaerophiles: metabolize O2, only grow in low O2
Facultative anaerobes: metabolize O2 in it’s presence, ferment in it’s absence.
Aerotolerant: do not metabolize O2 but ferment in the presence or absence of O2
Anaerobes: do not metabolize O2 and do not grow in its presence.
How do you tell aerobes (such as P. aeruginosa) from facultative anaerobes (such as E. coli)?
Aerobes use Cyt C as terminal oxidase while facultative anaerobes use Cyt D.
Oxidase test: cyt C oxidase reacts with indicator compounds upon oxidation reaction and will change in color to blue.
Describe the mixed acid fermentation done by enterobacteriaceae? What species do this?
Uses glycolysis to make pyruvate from glycolysis and then makes lactate, acetat + CO2, and formate from pyruvate.
Formate can be made into ethanol, or if the environment is too acidic it will be made into CO2 and H2 gas via formate dehydrogenase.
E. coli and salmonella can do this reaction with formate dehydrogenase rxn. Presence of this gas is a diagnostic test for these species.
What are the four phases of bacterial growth?
- Lag phase: no cell division, adaptation, and increased metabolism.
- Exponential phase: balanced growth
- Stationary phase: decreased nutrients, change in pH, buildup of toxic end products.
- Death phase: eventual, slow varies with species.
What are physical requirements for the growth of bacteria?
- Oxidation and reduction. Oxygen for aurobes and no oxygen for anaerobes.
- Temperature: most pathogens are mesophilic and have an optimum temp of 20-40 degrees celsius.
- pH: usually between 7.2 and 7.6. Some have formate dehydrogenase to neutralize acidity of environment (such as that of the stomach).
- Osmotic conditions: most tolerate only moderate salt concentrations
What are halophiles?
Bacteria that are isolated from high salt environments and require up to 30& salt for growth (5M NaCl equivalent).
How can you utilize osmotic sensitivity for selection of microbes?
Selective media: mannitol salt media is 7.5% NaCl and selects for gram + by inhibition of gram -.
This will select for staph aureus but inhibit escherichia coli.
