Notes Microbio

Sterilization

UV Sterilization
Ionizing Radiation
Antimicrobial Agents

Molecular Microbiology

Macromolecules and Genes
- Genes - functional unit of genetic information
- Genome - total genetic information (chromosomes + plasmids)
- Structure
  - Purine - Pyrimidine pairs (to maintain consistent width)
    - Pyrimidine (Cytosine, Thymine, Uracil) - two less nitrogen, one less carbon, single hexagonal ring
    - Purine (Adenine, Guanine) - hexagonal ring plus a pentagonal structure
  - G-C bonds are triple bonded, A-D double bonded -> more G-C bonds found at higher temperatures
  - DNA forms a double helix
  - Enzymes interact with the major groove
  - In prokaryotes, usually there is one chromosome, and it is circular
    - Borrelia burgdorferi (Lyme Disease) has weird chromosomes - linear chromosomes, both linear and circular plasmids
  - Agrobacterium tumefaciens -> used for DNA editing in plants, forms "tumors" on plants
  - Nucleoid -> Not enclosed with membrane, chromosomes supercoiled and bonded to a central protein core
  - Operons -> genes that activate together as a group

E. Coli chromosome
- 4288 protein-coding genes
- More than 300 plasmids (that we know about)
- Roughly the same number of genes on each strand (())
Plasmids
- Modular, small, typically circular additions to the genome outside of the chromosomes
- Not essential genes, just little add ons
- Copies - 1-3, to hundreds
- Plasmids can be lost, some plasmids have mechanisms to ensure they are passed down
- Plasmid Functions
  - Resistance plasmids (R plasmids) - give bacteria antibiotic resistance, toxic metal resistance, also helpful for genetic manipulation
  - Virulence plasmids - anthrax toxin in Bacillus anthracus, Animal cell invasion (Salmonella, Shigella) adherance fimbrulae in E. Coli -> extra tools
  - Nod factors - Rhizobium with certain plasmids that allow them to interact with specific plants
  - Antibiotic production - streptomyces
  - Metabolic functions - pigment production (Erwinia, Staphylococcus), gas vesicle production (Halobacterium), degradation of herbicides (Alcaligenes)

Gene Transfer in Bacteria

Horizontal Gene Transfer - unidirectional transfer of genetic material between unrelated organisms, =/= vertical inheritance
- Transformation - genetic transfer by which free DNA is incorporated into competent cells (possessing special proteins for transformation) - like dumpster diving
  - Any prokaryotic cell can be made competent - if Ca added, then chilled, or by electroporation (basically rip some holes in the cell)
- Transduction - genetic transfer mediated by a bacteriophage
- Conjugation - transfer of plasmids between prokaryotes, plasmids encode for their own ability to be transferred, through cell-cell contact (not necessarily docking up against each other, may be pili) can occur between different genera!
  - The F plasmid ("fertility" plasmid)
    - Transposons/Transposable elements - IS3, IS2, Tn100 - facilitate integration into host chromosome
    - tra region contains genes needed for conjugative transfer (formation of sex pilus)
    - Sends one strand of the plasmid into the F- cell, then makes the complement strands

Page updated

Google Sites

Report abuse