Bacteriology Cheat Sheet

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Qualities of Gram positive:

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Purple - Many peptidoclycan layers (holds blue stain)

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qualities of Gram negative:

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Pink - Outer membrane LPS and pores, few layers of peptidoglycan. Periplasmic space between layers of peptidoglycan.
Peptidoglycan: N-acetylglucosamine and N-acetylmuramic acid strung together in chains forming a mesh. (penicillin inhibits cross linking)
Periplasmic space:
LPS:
1) O polysaccharide: repeat 5 sequences of galactose, glucose, rhamnose, mannose. Antigenic
2). Core polysaccharides: glucose, heptose, galactose,
3). Lipid A: toxic, internal not seen by immune system.

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Bacteria morphology:
Capsule:

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Outer polysaccharide layer on some bacteria, slimy, involved in attachment, resistance to phagocytosis.
Glycocalyx: slimy outer layer in some bacteria, Involved in adhesion, biofilm formation.
Pilus or fimbria: Surface structure, very important in attachment of mucosal pathogens
Sex Pilus: rod protruding from surface, involved in transfer of DNA between bacterial cells.
Spores: Encapsulated genetic material. Made during hard times. Can remain in soil for a long time. Hightly resistant.

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Gaseous environment:
Obligate aerobes:
Facultative anaerobes:
Aerotolerant anaerobes:
Microaerophilic :
Obligate Anaerobes:

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Gaseous environment:
Obligate aerobes: need o2
Facultative anaerobes: Can grow with out o2 but shift to aerobic respiration in presence of air.
Aerotolerant anaerobes: Survive in air but don’t use it.
Microaerophilic :Prefer reduced oxygen
Obligate Anaroebes: Cannot tolerate O2.

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Describe the Regulation of metabolism

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Regulation of metabolism
1. Negative feedback loops:. End product feeds back to stop enzyme synthesis
2. Repression: End product activates a repressor which shuts down the transcription of the enzyme
3. Induction: Repressor protein is inactivated by the substrate that normally blocks transcription. In Substrate induces production of the enzymes needed for its metabolism.
Two component regulatory system: bacteria responds to the outside environment.

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Method of genes transfer?

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Method of genes transfer
Reciprocal recombination: replace areas of host DNA
1. Transformation: Takes up free DNA from media
2. Transduction: involves bacteriophages: viruses that infect bacteria and transduct bacterial genes into new bacterium.

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Affects of bacteriophages on the cell?

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Affects of bacteriophages on the cell:
a. Lytic cycle: bacteriophage takes over metabolism of cell forcing it to make lots of copies of the phage and then causes bacteria to lyse releasing bacteriophage.
b. Lysogenic cycle: mild bacteriophage infect bacteria. Pro-phage integrates into host DNA. When bacteria divides it contains DNA of bacteriophage too.
Phage conversion: Bacteria not harmful until infected by a prophage with the gene that encodes for the toxin.

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Two types of transduction?

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Two types of transduction:
a. Generalized transduction: Lytic phage picks up fragments of host DNA causing cell to die. Phage moves to another bacteria bringing DNA with it Bacteriophage cannot replicate but new bacteria now has acquired DNA from dead bacteria.
b. Specialized transduction: When phage makes copies of itself in host bacteria the host DNA adjacent to the phage may get packaged up with the phage.

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Bacteria SEX:

Conjugative: larger 2-3 copies per cell, transferred btwn cells via the sex pilus carry F fact
F Factor: codes for the sex pilus in F+ bacteria. Plasmid can be transferred to a F- bacteria so it becomes an F+ and then transfer the F factor to other F - bacteria. F Factor is safe but the plasmid may contain other bits of DNA that are not.

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Bacteria SEX:


Conjugative: larger 2-3 copies per cell, transferred btwn cells via the sex pilus carry F fact
F Factor: codes for the sex pilus in F+ bacteria. Plasmid can be transferred to a F- bacteria so it becomes an F+ and then transfer the F factor to other F - bacteria. F Factor is safe but the plasmid may contain other bits of DNA that are not.

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Non-conjugative:

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Non-conjugative: small multi-copied hundreds of little circle DNA present in cell. No good.

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Moveable genetic elements?

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Moveable genetic elements: DNA rearrangement.
Insertion sequencing: Short DNA sequences, with inverted repeats on either end so it reads the same in both directions.

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Transposon:

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Transposon: The insertion sequence sandwich other information, so instead of the insertion sequence getting dupliated and mobilized the whole thing gets duplicated and mobilized. They get copied and put somewhere in the genome “Jumping genes”.

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Conjugative transposons:

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Conjugative transposons: Have the transposon arrangement but also conjugate themselves meaning they code for transmission, don’t have a sex pilus.

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Antimicrobial Agents:

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Antimicrobial Agents:
Sulphonamides and Trimethoprin: Synthetic agents, Not anitibiotics. block the production of folic acid.
Pencillins and Cephalosporins: interfere with cell wall synthesis, effective on Gram + bacteria
Vancomycin and bacitracin: toxic, alter cell wall synthesis affecting cell membrane
Identification of bacteria:

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Pathogenetic Islands:

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Pathogenetic Islands: Large chunks of DNA acquired from other bacterial species, makes recipient bacterium pathogenic.
Integron: go around picking up random DNA and contain an integrase.

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3. Conjugation:

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3. Conjugation: transfer of plasmid DNA through a sex pilus from one bacteria to another.
Plasmids: Small closed circles of extrachromosomal DNA, information for autonomous replication.