impact of symbiosis on human health and disease

Lecture 16 MICR221

pathogens

bacteria that cause disease

commensals or mutualistic bacteria (3)

• don’t cause disease

• benefit from association with humans

• can provide benefits to humans (mutualistic)

symbiosis

‘living together’ of two organisms

commensalism

relationship where one organism benefits and the other is neither helped nor harmed

mutualism

relationship where both organisms benefit

pathogenesis

relationship where one organism is harmed

ways bacteria ‘help create us’ (3)

• intestinal flora help with human nutrition

• stimulate proper growth of intestine and immune system

• perturbation of normal bacterial flora can contribute to disease

areas of body colonised by commensal/mutualistic bacteria (5)

• skin

• oral cavity

• nasopharynx

• stomach

• gastrointestinal tract

classic approach to identifying bacteria that colonise certain sites in the body

culturing

limitations of culturing (2)

• many microbes in human body can’t be grown in lab conditions

• labour-intensive

modern approach to identifying bacteria that colonise certain sites in the body

DNA sequencing of 16S rRNA

what does the modern approach (DNA sequencing) allow

identification of bacteria at the genus level