Question

There are over 150 known strains of bacteria that are considered normal human flora.

A. What are some factors enable these “normal biota” to become pathogenic and invade the host? [I am looking for microbe Virulence factors]

B. Explain why some bacteria infect specific tissues or regions of the host. (This was in the movie, Bacteria and Humans)

C. What are some properties of the bacteria that allow these organisms to evade host defense mechanisms?

Answer 1

A. When normal microbiota becomes pathogenic it may be due to one of the following reason-

1. The host becomes immunocompromised

2. Mutations in the virulence factor genes lead to the increased pathogenicity

3. Mutations in the host proteins/ enzymes may lead to uncontrolled proliferation of normal biota or expression of the particular pathogenic protein.

B. Tissue specific infenction:

To infect the human cell or tissue the cell should posses the receptor on its surface that is recognised by pathogenic bacterial species and infect the cell or tissue. Receptor-mediated endocytosis is one of the examples.

C. properties of the bacteria that allow these organisms to evade host defence mechanisms

Bacteria may secrete proteins/ enzymes that cause degradation/ dysfunctioning of host components and there by controlling the host immune system. In majority of viruses this is the case.