Question

Microbiology Mini-Tutorial: the Human Microbiome

Answer 1

Note: This is a reference for educational/studying purposes, not a question, please save all comments or questions for the end.

Answer 2

- total: 3 * 10 ^ 13 microbes
- obstacles to microbial growth: pH, temperature, moisture, secretion of antimicrobial chemicals/molecules
- can exhibit mutualism/parasitism/commensalism

\({\bf{Skin}}\) 10 ^ 11 - 10 ^ 12 microbes, often on upper layers of epidermis + hair follicles
- species: propionibacteria (often implicated in acne/skin problems), Staphylococus epidermis, Corynebacteria

\({\bf{Oral}}\) 10 ^ 10, often in peridontal pocket/cavities
- species: Streptococus mutens, which produce lactic acid to change the pH of the tooth, implicated in cavity formation
- endocarditis: infection of the heart chamber lining when bacteria spreads from the mouth through the bloodstream

\({\bf{Blood}}\) [not sure about the # count, can't find a good source in my notes/online], either enter the blood from the body or from a foreign source like a transfusion/injection
- species: Strep, Staph, E. coli, Pseudomonas

\({\bf{Respiratory}}\) [can't find a good source for count #], nose/nasal passages
- species: Strep, Pseudomonas, Enterobacter

\({\bf{Gastrointestinal Tract}}\) 10^13 [vast majority of bacteria here]
- species: Heliobacter pylori (ulceres)
- bacterial samples often obtained from large intestine

Answer 3

\({\bf{Koch's~Postulates}}\) criteria to prove that a certain microbe is responsible for a disease rather than an external factor
1. microbe must be present in all cases of the disease
2. pathogen must be isolated and grown in pure culture
3. isolated pathogen must cause disease when incorporated into healthy gnotobiotic animal
4. pathogen must be isolated from the diseased animal

caveats: might not work if the disease is caused by multiple microbes or if the microbe cannot be isolated/grown in culture