Question

1)Some bacteria found in waterways have a capacity for buoyancy. Explain the molecular, genetic and structural aspects involved in microbial buoyancy.

2) Virulence factors can be defined into two major classes. Describe ONE (1) of these classes.

Answer 1

The net force on the bacterium should be positive for flotation to occur. It is believed that the bacteria will increase in volume as a result of gas vesicle production.

Some aquatic bacteria can make intracellular chambers (made entirely of proteins) that are permeable only to environmental gases. The structures are called as gas vesicle (GVs) and they form conglomerates (gas vacuoles) identifiable by phase microscopy. The aquatic bacteria that make GVs may use them for the phenomenon of bouyancy, allowing upward flotation in a static water column. This ability can be useful for se photosynthetic bacteria (cyanobacteria) that need to rise in a stratified aquatic niche to access light of a specific wavelength, or to acquire nutrients or oxygen at the air-liquid interface, or perhaps to escape predators or competitors. The GVs usually comprise a major protein (GvpA) and a minor protein (GvpC) and form cylindrical structures with apical poles.

Bacteria produce a wide range of virulence factors which cause host tissue pathology, and these diverse factors have been grouped into four families: adhesins, aggressins, impedins, and invasins.

A major group of virulence factors are bacterial toxins. These are divided into two groups: endotoxins and exotoxins.

Endotoxins- the lipopolysaccharide endotoxins on Gram-negative bacteria cause fever, changes in blood pressure, inflammation, lethal shock, and many other toxic events.