They are able to sense the presence of certain nutrients in their environment and move toward them and they are able to move away from harmful substances. Using flagella, bacteria are able to respond to environmental stimuli. Bacteria can have multiple flagella that surround the cell, a few flagella on one or both ends of the cell, or a single flagella. Bacteria can be divided into several types based on several characteristics such as shape, cell wall composition, mode of respiration, and mode of nutrition. These structures move in a circular motion to propel the bacteria forward. Bacterial Nucleus Endospore of a bacteria Shapes and Arrangement of Bacteria a. Some, but not all, bacteria have one or more flagella. Because it has no cell wall it can have a variety of shapes.ģ) flagella –a whip-like structure used for movement.
Mycoplasma pneumoniae is an example of a cell wall-less bacteria. E.Coli and Salmonella Spiral-shaped bacteria (Spirilla) e.g. Staphylococcus and Streptococcus Rod-shaped bacteria (Bacilli) e.g. Vibrio Cholera Spherical-shaped bacteria (Cocci) e.g. Shapes of bacteria Comma-shaped bacteria e.g. They have, instead, chemical compounds which protect the bacteria against drying out and they usually live in environments in which osmotic pressures are not a problem for survival. Most of the bacteria can be classified into the following shapes. Examples include the streptococcus group. coli (stained pink).Ī few bacteria do not have cell walls. Spherical: Bacteria shaped like a ball are called cocci, and a single bacterium is a coccus. The image at the left as seen through a microscope shows both Gram-positive (stained dark purple) rod-shaped bacteria, Bacillus cereus, and the smaller Gram-negative rod-shaped bacteria E. Are bacteria different shapes Individual bacteria can assume one of three basic shapes: spherical (coccus), rodlike (bacillus), or curved (vibrio, spirillum, or spirochete).
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