Bacteria and Viruses

Bacteria are unicellular organisms called prokaryotes. Viruses are pieces of biomolecules that cannot reproduce independently. Both groups may be pathogens, or may be beneficial- sometimes, the same species or variety may be both, depending on circumstances (Starr, C., and Taggart, R., 2004.) Throughout history, pathogens and more helpful species have played vital roles in the development of humanity as a species and of the human social arrangement.

Prokaryotes are divided into eubacteria and archaebacteria. Eubacteria are considered bacteria, and will be henceforth referred to as such. Archaebacteria lived in more extreme environments, are older than eubacteria, and have sufficient chemical differences to be distinct from bacteria. Prokaryotes are unicellular organisms that reproduce through fission and conjugation, have great metabolic diversity, have a single chromosome arranged in a circle called a plasmid with no nuclear membrane, and tend to have cell walls. One of the most notable characteristics is the lack of membrane-bound organelles, such as lysosomes or the endoplasmic reticulum. Bacteria have three types of shapes: coccus, bacillus, and spirillum (Starr, C., et al, 2004). Cocci are sphere-like and are around .5 to 1 µm long, bacilli are rod-like and 0.5-1.0 µm wide by 1.0-4.0 µm long, and spirilli are spiral-shaped and vary from 1 µm to over 100 µm in length (Elert, G, 2006.) Designations of this type may be made more precise through addition of morphemes to the front of the word, such as in the case of diplococcus, which means a pair of spherical bacteria. Gram-negative bacteria have an additional coating beyond the cell wall, called a capsule. These capsules have lipopolysaccharide in them, which is toxic and caus...

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