Bacterial Nutrition Flashcards
Treponema Pallidum
Some bacteria grow only in living animas
- Causes Syphillus
- Needs to be grown in rabbit testicles
Mycobacterium Leprae
Some bacteria grow only in living animals
- Causes leprosy
- Can be grown in mice or armadillo
Three techniques to isolate organisms
Enrichment - has only the min reqs needed for growth
Selective - Selects growth of some while inhibiting growth of others
Differential - Other orgs can also grow, but it highlights a specific org. ex with EMB, only lactose fermenters stain black while non lactose fermenters can grow but look clear
Eosin Methylene Blue (EMB)
Promotes Enteric Gram - Rods ie Enterobacter
Inhibits Gram +
Lactose Fermenters appear purple or metallic green
Blood Agar
Not Selective
Hemolysis patterns seen
Promotes growth of many bacteria
Mannitol Salt
Pink, Has high salt solution that a lot of bacteria can’t survive in.
Selects for Staph (Gram +)
Mannitol Fermentation is Yellow (Golden Staph)
MacConkey Agar (MAC)
Promotes Gram - (Enterobacter, Serratia, Klebsiela)
Lactose Fermentation turns pink
Beta Hemolysis
looks a yellow clear zone around the colonies
Pathogenic
Alpha hemolysis
Normal Flora
Bacteroides Fragilis
Obligate Anaerobe that cannot survive in presence of O2
Common in abdominal abscesses
What two critical enzymes to Obligate Anaerobes Lack
Superoxide Dismutase & Catalase
High O2 tension can be used to treat infections with these bugs
Pseudomonas Aeruginosa
Obligate Aerobe that causes nosocomial infections
Requires O2
Bacillus Anthracis
Obligate Aerobe used in bioterrorism
Clostridium Tetani
Obliage Anaerobe that causes tetanus
Why is O2 required for obligate Aerobes?
They lack PFK, phosphofructose kinase
Cant make enough E from glycolysis alone
Make triose phosphates using Pentose Shunt
Can only offset the O2 deficit by Ox-Phos
What Element is critical for all bacteria
Iron
It is in S containing compounds, as well as E carriers
Most Fe in Fe3+ state, can only use Fe2+
Bacteria have made Fe Transport systems
What is a Siderophore
Its a Fe3+ Specific Ligand that bind bacterial membrane receptors to bring in the Fe3+ that will then be reduced to Fe2+ inside the bacterium
Difference btwn E. Coli & Shigella Dysenteriae
E. Coli: -Can ferment lactose -Normal flora of the gut -Resistant to Acid Shigella -Cant ferment lactose -Not normal flora, indicates disease -Low acid secretion (in malnutrition) predisposes to Shigella infection
Diff btwn E. Coli & Enterobacter Aerogenes
Enterobacter: -Gram - Rod Produces Acetoin Normally present in field water E. Coli: -Gram - Rod Doesn't produce Acetoin Indicative of Sewage Contamination
What organism converts pyruvic acid to ethanol?
Yeast
How can some bacteria make ethanol?
By converting pyruvate–>Acetyl CoA–>Acetylaldehyde–>Ethanol
What are the two monomers for peptidoglycan?
N-Acetyl Glucosamine (NAG) & N-Acetyl Muramic Acid (NAM)
NAG makes NAM
How is NAM made from NAG?
NAG + PEP = NAM.
This is blocked by Fofsomycin
What does NAM require in order to be complete?
The addition of 5 Amino Acids. This is NAM pentapeptide
This step is blocked by Cycloserine
What does Fofsomycin and Cycloserine antagonize, respectively?
PEP to block NAM synthesis
D-Alanine to prevent AA addition to NAM
What are the three process required for making peptidoglycan?
Pep Monomer
Ext of the Chain
Cross Linking of glycan strands
Extension of Pep Chain
NAG & NAM pentapeptide are linked in alternating chain
This is blocked by bacitracin
Crosslinking (Vertical) of Pep layers
This is how the “thickness” of the peptidoglycan wall is achieved. In gram - there is only one layer so there is no cross linking. In gram + there multiple layers cross-linked
This is inhibited by many Anitbx such as Beta Lactams (penicillin, cephalosporins) and vancomycin
What is the enzyme needed to X-Link Pep layers?
Transpeptidase
This is where the antibx attack to prevent crosslinking
Which class of bacteria have a thicker cell wall? Who is more restrictive?
Gram + have a thicker cell wall, but the outer membrane of gram - bacteria is more restrictive
What are the 3 phases of bacterial growth
Lag, Exponential or Log & Stationary
Describe the Lag Phase
This is the phase where protein synthesis is occuring. It takes a moment for the bacteria to get ready to start dividing
Describe the Exponential or Log Phase
This is the phase where the bacteria divide rapidly. It also the time when the patient can get very sick very quickly so it may be wise to treat with an Antibx right away before getting Blood Cx results.
Describe the Lag Phase
This is the phase where the bacteria has run out of nutrients and can no longer support division. This can mean death of the host.
Doubling Time for Bacterial Growth tD
This is the mean generation time, and its the time it takes for the bacteria to double itself. If this time is small, then the bacteria grows very fast.
Instantaneous Growth Rate for Bacteria (alpha)
Basically a faster growth rate means a shorter doubling time. So the larger the the growth rate, the faster it grows and the shorter the doubling time
Exponential Growth Rate of Bacteria (u)
The larger it is the faster it grows
