They exist everywhere, around, on, and inside every single plant, animal, and
human being in the planet. Without them no life would be possible, indeed, life would
never have even flourished on Earth. Bacteria are, without a doubt, the most important
organism in all the kingdoms of life. While the all the good bacteria do is well
documented, their negative effects, especially on humanity, are much more known. By
describing and comparing the most important details of two of the more important
bacteria species, a general overview of the pathogenic (harmful to humans) bacteria will
Bacteria are simple single celled organisms that feature small circular DNA, cell
division by binary fission, lack of internal compartmentalization, singular flagellum, and
metabolic diversity (Raven et al, 2008). They are much simpler than Eukaryotic cells and
differ from the other types of prokaryotes, Archaebacteria in four key areas: Plasma
membranes, cell walls, DNA replication, and gene expression (Raven et al, 2008).
Bacteria have three basic shapes. Bacilli (singular: bacillus) are rod shaped while coccus
are roughly spherical and Spirillum are long and spiral shaped, as the name would imply.
Bacteria have tough cell walls made of peptidoglycan. Depending on the
thickness and arrangement of the wall, the bacteria is either gram-positive or gram-
negative (referring to the ability of the cell walls to retain crystal violet dye). This cell
wall enables bacteria to survive in a variety of environments. Even the stomach whose
gastric juice, because of its acidity, may destroy many types of bacteria may not affect
certain types of pathogenic bacteria, such as
may survive this
acid medium and produce Gastrointestinal or systemic infection (Bellanti, 1978).