Human Microbiome Symbiosis

1. Human Bodies: 70-90% Microbial Cells, 10-30% Human Cells

2. harmful microbes

2.1. parasitic symbionts (parasitism)

2.1.1. true pathogens

2.1.1.1. cause disease in both immunocompromised people and in immunocompetent people

2.1.2. opportunistic pathogens

2.1.2.1. cause disease in immunocompromised people

2.1.2.2. change in circumstances (change in location in the body)

3. microbes that have no effect

3.1. commensal symbionts (commensalism)

3.1.1. most of the microbiota

3.1.1.1. examples

3.1.1.1.1. Demodex folliculitis

3.1.1.1.2. Malassezia globosa

3.1.1.1.3. Dental plaque/biofilm (many species)

4. helpful microbes

4.1. mutualistic symbionts (mutualism)

4.1.1. examples

4.1.1.1. microbial antagonism

4.1.1.1.1. microbes are fighting each other; helps to maintain a balanced community of microbes (homeostasis)

4.1.1.2. stimulation of immune system

4.1.1.2.1. examples

4.1.1.3. vitamin production

4.1.1.3.1. examples

4.1.1.4. digestion

4.1.1.4.1. examples

5. symbionts that are usually harmless by themselves but can sometimes work together to cause a synergistic infection (synergism)

6. symbionts can sometimes work together to create biofilms (microbial communities) which can be harmful

7. mutualistic symbionts contribute greatly to human body homeostatis; sometimes our normal microbiota are referred to as "microbial organs"