Bacterial Metabolism Flashcards
Name features that distinguish prokaryotes from eukaryotes
Prokaryotes have:
- A single, circular chromosome instead of a nucleus with multiple chromosomes
- No nuclear membrane or mitotic apparatus
- Transcription coupled to translation.
- Ribosome is 70S instead of 80S; moderate differences in shape and function. Target for antimicrobial agents.
- Cell Wall with unique residues and structural organization. Target for antimicrobial agents
- Simple cytosolic organizations: no endoplasmic reticulum, mitochondria or other organelles; bacteria have a complex plasma membrane
What is the fundamental unit of taxonomy
species
Describe the species boundaries/definition in eukaryotes
- sharp natural species boundaries
- Species are defined by the ability to produce fertile offspring
Describe the species boundaries/definition in prokaryotes
- no sharp natural species boundary
- Species defined by genetic relatedness and possession of similar physiological function
Describe multiplication in prokaryotes. what is this called
Multiplication is asexual, where each individual cell gives rise to two identical offspring-binary fission
Molecular identification of bacteria
Relationships among bacteria are reflected in their DNA composition
- amplification techniques
- genome analysis and sequencing techniques
Advances over current classical molecular techniques for molecular identification of bacteria are
- automation (productivity)
- speed (rapid)
- greater accuracy (fewer false positives)
Polymerase chain reaction (PCR)
-Amplification of pathogen specific DNA (potential for rapid identification)
*identify slow growing- or non-cultivable- bacteria
*Rapid identification (Example, amplify the gene encoding Clostridium
difficile toxin from stool of an individual with antibiotic-associated
pseudo-membrane enterocholitis
Restriction fragment length polymorphism (RFLP)
Analysis of restriction endonuclease patterns of the bacterial chromosome
-Used during hospital acquired (nosocomial) infections to determine the
source of an infection
example: During a bacterial infection
-(RFLP of isolates are identical between patient and personnel) bacterium infecting
patients hospital associated: single source (personnel) of infection)
-(RFLP of isolates are different between patient and personnel) Infection community
associated from multiple sources
-this doesn’t show causal associations but does show temporal
• hospital associated and community acquired infections are often treated
differently
What is a good way to identify liptospira
Analysis of unbiased next-generation DNA sequencing of the host tissue
(cerebrospinal fluid)
identification of a prokaryotic species based on biochemical and biological methods (Morphology)
Morpholgy:
- colony morphology
- cell shape, gram stain, motility (leptospira)
- presence of capsules
Biochemical:
- ability to metabolize specifici substrates
- -production of specific end products
- antibiotic sensitivity
overview of metabolism
Glucose is converted to pyruvate which
- in the presence of oxygen can metabolized via respiration into CO2 and H2O. This process is energy efficient.
- in the absence of oxygen is metabolized to organic end products. This has little energy production and is uniques to microbes (aka diagnostic)
Whether a bacteria does respiration or fermentation depends on what
-the ability of the organism to metabolize oxygen
aerobes
metabolize O2; grow only in its presence
Microaerophiles
metabolize O2; grow only in low O2
Facultative anaerobes
metabolize O2 in the presence of O2; ferment in the absence (metabolically diverse)
Aerotolerant
do not metabolize O2; but ferment in the presence or absence of O2
Anaerobes
do not metabolize O2; do not grow in the presence of O2 (gut bacteria)
OXIDASE TEST
Differentiates aerobes from facultative anaerobes:
- Aerobes (Pseudomonas aeruginosa) use Cytochrome C as the terminal oxidase.
- Facultative anaerobes (Escherichia coli) use Cytochrome D as terminal oxidase
- In the OXIDASE TEST: Cytochrome C oxidase reacts with indicator compounds upon this oxidation reaction (scored as a change in color, blue)
So if it is an aerobe it will appear blue
Why is fermentation diagnostic
because fermentations are unique to species of bacterium
Mixed Acid Fermentation: Enterobacteriaceae
-DIAGNOSTIC KNOW THIS
- Glucose is converted to pyruvate via glycolysis
- pyruvate is broken down to lactate and acetate and CO2.
- pyruvate is also broke down to formate which via NADH2 to NADH is converted to ethanol
under acidic conditions: Formate vai formate dehydrogenase is converted to CO2 and H2 (so gas is produced) this can be used as a diagnostic test bc E. coli and Salmonella convert formate to Co2 and H2 but Shigella and S. typhi do not. SO you can grow it in a test tube and look for gas
-3 key points about Fermentation
- each fermentation gives the bacterium a selective advantage in the environment
- use for targeting of anti-microbial agents
- diagnostic
4 phases of bacterial growth
- lag-NO cell division: adaptation; increased metabolism
- Exponential: Balanced growth
- Stationary: decrease nutrients, pH change, buildup of toxic end products
- Death: eventual, slope varied with species
List the types of bacteria based on how much they like to grow in oxygen, starting from least to greatest
obligate anaerobes aerotolerant anaerobes facultative anaerobes microaerophiles obligate anaerobes
What temp range are most pathogens able to grow in and what are organism that grow in this temp range called
Mesophilic
Range: 10-45
Optimum: 20-40
pathogenic bacteria usually grow between what pHs
7.2 and 7.6
osmotic conditions
- most bacteria tolerate only moderate salt
concentrations.
- most bacteria tolerate only moderate salt
- Halophilic are an exception
- Isolated from high salt environments (salt flats)
- Require up to 30% salt for growth
(5. 0 M NaCl equivalent)
-osmotic sensitivy can be used for selection of microbes
Describe the selective media Mannitol salt media
7.5% NaCl- Selects for Gram positive, by
inhibition of growth of Gram negative
so if something grows on mannitol salt media then it must be gram positive
Instead of entering the death phase of the life cycle, some bacteria can
- go from a vegetative cell to a spore
- most bacteria die with prolonged exposure to the stationary phase, unless the for a spore
Sporulation
- unique property of a subset of bacteria:
- Bacillus (G+ aerobe)
- Clostridium (G+ anaerobe)
- Response due to ↓ in supply C, N, or P
- Spore -Dormant structure capable of survival for prolonged periods; with capacity to reestablish the vegetative life style
- example of unicellular differentiation
Spore
-Dormant structure capable of survival for prolonged periods; with capacity to reestablish the vegetative life style
Three steps of sporulation
- DNA synthesis
- asymmetric cell division
- DNA packaging
describe spores and staining
spore is refractive to stains
germination
what is it and what is required
- when a spore becomes a vegetative cell
- spores may remain dormant for 100s of years and then with water and metabolites (amino acid, sugar) they can become vegetative cells again
How to inactivate spores
- they are EXTREMELY heat resistant.
- You must autoclave them
- Wet heat, 120 degrees celcius for 20 minutes
- autoclave sterilizes
