Bacterial Physiology

Flagella are a part of certain bacterial species. This are thin, rigid protein-containing structures that confer motility to the organism. They use ion transfer across the cell membrane electrochemical gradient to allow for mobility. Fimbriae, on the other hand, are also referred to as attachment pili. These are much thinner than flagellae and are distributed throughout the cell surface. These allow for attachment of the organism to surfaces. Pili are also appendages on a bacterial cell that allow for the transport of genetic material between two bacterial cells. These can be called conjugation pili or sex pili because of the exchange of genetic material.

Many bacteria have a glycocalyx layer around the cell that can be similar to a capsule or even a slime layer that prevents complete engulfment by macrophages and other cells of the immune system in animals. They are also part of the recognition process of bacteria by the immune system and of the recognition of bacteria by each other—participating in the formation of bacterial biofilms. These types of structures are secreted from the bacteria themselves into the periplasm around the organism. These extra layers around bacteria will contribute to their virulence.

Endospores are structures made by certain Gram-positive bacterial species (like Clostridium, Bacillus, Heliobacterium, and Anaerobacter species). These develop within the cytoplasm itself, with one endospore per cell. There is a DNA and ribosome core and a cortical layer that is rigid and made of peptidoglycans. They do not metabolize and resist extreme conditions of all types, viable for millions of years. Examples of sporeformers in human diseases include anthrax (from Bacillus anthracis) and tetanus, called by Clostridium tetani.

BACTERIAL PHYSIOLOGY

For being such small organisms, one would think that they do not have much in the way of metabolism. And yet, there are many different metabolic types of bacteria. Bacteria can derive their energy from light in the process of photosynthesis (also called phototrophy) or using the breakdown of other chemical compounds, also called oxidation or chemotrophy. Chemotrophic organisms use terminal electron acceptors