- Microbiology
The types of Prokaryotic cells (Kingdom Monera) we are most familiar with are the Bacteria. When most of us think of bacteria, we picture disease, infection, pus,
rotting
or even death. However,
not all bacteria cause disease. In fact, most bacterial species cannot cause
disease. Many species even play beneficial roles in, say, producing antibiotics
and foodstuffs. The soil teems with free- living bacteria that perform many
essential functions in the biosphere. Our bodies are covered with
bacteria (called our
normal flora). Even among bacteria that are
capable of causing disease, few, if any, species are
always pathogenic. The different types of micro-
organisms found in the human body are not uniformly distributed throughout
the body as each site constitutes a unique ecological niche and is characterized
by a unique variety of normal flora. It has been estimated
that there are more bacterial cells associated with the average
human body than there
are human ones and one of the most important functions of our normal
flora is to protect us from highly pathogenic organisms.
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It is important to realize that there is a balance between ourselves as host and our indigenous flora, (that we casually call good health). Chronic or acute disease conditions may result if this balance is disturbed due to diet variations, antibiotic therapy, personal hygiene, use of antimicrobial soaps, feminine hygiene products, contraception methods or mechanical damage. In addition, the normal microflora usually contain small numbers of pathogenic microorganisms, which are able to cause disease, held in check by the competitive and predominantly beneficial microflora.
A few of our normal flora produce essential nutrients (e. g. vitamin K is produced by gut flora) and our normal flora may prevent pathogenic microorganisms from getting a foothold on our body surfaces. Antibiotics can have an effect on the normal flora as well as the bad ones and can result in their being replaced with pathogenic organisms, such as fungal or bacterial infections.
Like it or not, we have many large amounts of many types of bacteria growing almost everywhere in and on our bodies. About 10 percent of human body weight and 50 percent of the content of the human colon is made up of bacteria, primarily the species known as Escherichia coli, or E. coli. Bacteria and Archaea service their human hosts by handling a variety of gut functions, such as metabolizing sugars and amino acids and synthesizing essential vitamins, according to a recently published metagenomic analysis. Billions of bacteria also inhabit human skin, each square centimeter hosting an average of 100,000 organisms.
The
image on the left shows bacteria growing inside a human's mouth. The
small
red and green dots are different types of bacteria. The large red ovals
are cheek cell nuclei.
Bacteria are found on our: |
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Skin -Staphylococcus epidermidis, S.aureus, Streptococci
pyogenes, S. pneumoniae, and Neisseria. Mouth & throat - Streptococci mitis and S. salivarius, S. epidermidis, and Spirochaetes. Small intestines - Lactobacilli, Enterococci, and Mycobacteria. Large intestines - Bacteroides and Enterobacteriaceae (mainly E. coli). |
on to Pathogenic (disease-causing) Bacteria. 