Intro Flashcards
What does a gram stain test for
Cell wall
Gram positive
cell wall is thick and made of peptidoglycans, inner cell membrane that is lipid bilayer ( no sterol).
- stains purple
- has acids that are virulence factors
Gram negative
- cell wall is thin peptidoglycan layer
- 2 cell membranes (inner and outer) made of lipid bilayer (no sterol)
- stains pink
- very impermeable due to double bilayer, has porin channels
- LPS-causes symptoms distally and locally (fever, platelets)
Peptidoglycans
Form cell walls and cross-link to each other
Colonization v. Infection
Colonization=things are present
Infection=things present & cause symptoms either due to tissue damage or due to immune response to the toxin/bacteria
Skin bacteria
Normal: staphylococcus epidermis
Transient: staphylococcus aureus
Upper Respiratory Tract bacteria
Normal: viridans streptococci & anaerobes
Transient: neisseria, streptococcus pneumonia, haemophilus influenza
GI bacteria
anaerobes, enterococci
Genitourinary bacteria
lactobacillus
Bacterial Pathogenicity depends on…
host, environment & virulence factors
Virulence factors
slimes/biofilms, ability to evade phagocytosis & proteases, toxins, adhesions, flagella
Virulent v. opportunistic pathogens
Virulent–have virulence factors that cause disease
Opportunistic–lack classic virulence and only cause disease in immunocompromised ppl
Bacterial metabolism (4 kinds)
- anaerobic
- aerobic-make superoxide dismutase and catalase to eliminate toxic O2 byproducts
- facultative
- -microaerophilic–need a little O2
What can bacteria synthesize that we only get from our diet?
Folate
Cell replication in bacteria (2 enzymes)
DNA gyrase and topoisomerase allow chromosomes to unwind during replication
Bacterial evolution is due to…
mutations, acquisition of virulence factors and antibiotics, which select for resistant strains
Plasmids
are circles of DNA that can insert themselves into bacterial cells/DNA and get replicated
Bacteriophage
viruses that infect bacteria and insert themselves into the DNA to create a prophage
Why can DNA phages survive for a long time?
Due to a protein coat that helps transfer antibiotic resistance
Transformation
When a cell picks up free DNA from the environment
Conjugation
2 bacteria physically touch and an F+ cell transfers a plasmid to an F- cell to make it F+
Transduction
bacteria infected by viruses that code for virulence
