Motile bacteria move through the function of flagella. These appendages rotate, which propels an organism forwards. This is a little like the propellers on a boat. Some bacteria have one flagellum, others have many, and some possess none at all. Some of the bacteria regarded as human pathogens have flagella. An example of a flagellate bacterium is the ulcer-causing Helicobacter pylori, which uses multiple flagella to propel itself through the mucus lining to reach the stomach epithelium. Some flagella also serve a function in environmental detection, sensing different conditions and signalling to a bacterium to move to or away from a given niche.
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Although bacterial and fungi colonies have many characteristics and some can be rare, there are a few basic elements that you can identify for all colonies:
- Form - What is the basic shape of the colony? For example, circular, filamentous, etc.
- Elevation - What is the cross sectional shape of the colony? Turn the Petri dish on end.
- Margin - What is the magnified shape of the edge of the colony?
- Surface - How does the surface of the colony appear? For example, smooth, glistening, rough, dull (opposite of glistening), rugose (wrinkled), etc.
- Opacity - For example, transparent (clear), opaque, translucent (almost clear, but distorted vision, like looking through frosted glass), iridescent (changing colors in reflected light), etc.
- Chromogenesis (pigmentation) - For example, white, buff, red, purple, etc.