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They re out there! You can t see them but they can see you. Right at this very moment they are living on and in your body, and there is nothing you can do about it!

This may sound like the beginning of a horror movie, but it isn t. It is actually a very basic description of a very broad subject: microbiology.

Microbiology is a complex subject that spans out into a variety of areas. I am a person who is entering the health care field, and it is inparitive that I know the subject of microbiology and how if effects the world in which we live.

Part one of this essay will deal with defining bacteria, viruses, fungi, microbes, and pirons. Part two of the essay will focus on indigenous micro flora that is on and in the body, and part three will describe the structure and replication procedure of viruses.

Part one

As stated by Prescott, Harley and Klein (1990) microbiology is the study of organisms that are usually too small to be seen with the naked eye.

According to Jenson and Wright (1989) a pathogen is a disease-producing organism.

They also describe microbes as organisms that are often too small to be seen without the aid of a microscope. Microbes, also known as microorganisms, can be broken down into four classifications that are bacteria, viruses, fungi, and protozoa.

Prescott, Harley & Klein (1990) describe bacteria as prokaryotic cells (cells that lack a true membrane enclosed nucleus). Bacteria are both small and simple in structure; they usually are between o.5 and 5cmm yet they have many characteristic shapes and sizes. Some bacteria are circular or oval shaped, they are known as cocci bacteria. Other bacteria are rod-shaped, they are known as bacilli bacteria, and some bacteria are spiral and coil-shaped and it is know as spirilla bacteria.

Engelkirk & Burton (1979) state that bacteria can reproduce asexually by simple division of cells and some bacteria reproduce sexually by conjunction. A bacterium is a waste producer of products and secretions. This allows pathogens to invade their hosts to cause disease some of these harmful diseases are Scarlet fever, an acute illness, characterized by a reddish skin rash, which is caused by systematic infection with the bacterium streptococcus. St. Anthony s Fire is another bacterial disease. St. Anthony s Fire which is an acute superficial form of celluitus involving the dermal lymphatic, usually caused by infection with streptococci and chiefly characterized by a peripherally spreading hot, bright red, oedematous. It s medical name is Erysipelas (Jenson & Wright, 1989, p. 453). A third disease caused by harmful bacterium is Gonereah. A contagious bacterial infection spread through sexual contact, including vaginal, oral or anal sex. Also called “the clap,” it is one of the most commonly infectious diseases in the world. It is treated with antibiotics (Jenson & Wright, 1989, p. 452)

Viruses, as described by Englekirk & Burton (1979), are a particular type of microbes that are very tiny in design, and they are classified as living cells. Viruses, like bacteria, are classified as prokaryotes. Virus s conceits of a core of nucleic acid (DNA or RNA) surrounded by a protein shell. Some viruses have an outer lipid capsule. Viruses can cause disease and change the genetic make-up of a cell. They do this by injecting its DNA or RNA into the host cell. The host cell is then taken over by the genetic material of the virus. The infected host cell will then burst; thus infecting the surrounding cells. A disease caused by a harmful virus is A.I.D.S. Acquired Immune Deficiency Syndrome which is caused by the human immonodeficiency virus (HIV) (Jenson & Wright, 1989, p. 476) Another disease caused by harmful viruses is Rubella, (German measles) A viral infection which is dangerous to the fetus of pregnant women as it may cause various birth defects (Jenson & Wright, 1989, p. 477). A third viral disease is Influenza, Commonly called “the flu”, influenza is a virus that infects the respiratory tract and may cause fever, headache, and general body aches, runny nose, sore throat, or cough (Jenson & Wright, 1989, p. 477).

According to Englekirk & Burton (1979) the microbe, protozoa can be classified into the eucaryote division (organisms with a true nucleus). They are single-celled microorganisms that can either live in soil, water, living organisms, dead organisms, or decaying organisms. The different classifications of protozoa are divided into groups according to their mode of movement, or the presence or absence of cilia or flagella. Some protozoa can be pathogenic and cause serious diseases such as B. coil (Balantidum coli), malaria, and a diarrhea disease (cryptosporidiosis).

As told by Englekirk & Burton (1979) fungi, like protozoa, is classified as eucaryote organisms that include mushrooms, molds and yeasts. Fungi live on plants, animals, water and soil. Fungi are either harmful or beneficial. The fungi that are beneficial are very significant to the manufacturing of certain foods and beverages as well as some drugs and antibiotics. Fungi get their main source of food from dead or decaying organic substances. They do this by secreting digestive enzymes into the dead organic matter, which then decomposes into nutrients which is then used by the fungi and other living organisms. The fungi that are harmful can cause different types of diseases. Some of them are oral thrush, yeast vaginitis, and ringworm.

They also describe the Piron, (proteinaceaus infectious particle) as an infectious particle that is the cause of slow growing diseases. A Piron contains no nucleic acid, but it is made up of a protein called PrP.

Part Two

Eglenkirk & Burton (1979) describe indigenous microflora as microbes (bacteria, fungi, protozoa, and viruses) that are found normally living on the skin or in mucus membranes, or at all body openings. The growing conditions for indigenous microflora include moisture, pH, temperature, oxygen supply, and nutrients. These growing conditions are different all through the body. This allows for various types of indigenous microflora living from one body site to the another.

Microbes do not find the body to be a suitable place for residence, so very few types of normal flora live on and within the body. Yet in addition to the resident microflora found on and within the body, there is also transient microflora, which will live on and within the body temporarily. These transient microflora flourishes in the moist body areas like the mouth. They are only temporary because this transient microflora can be controlled by regular hygiene. They may also be flushed out by regular body functions such as urinating.

The destruction of the resident microflora leaves the body more vulnerable to secondary invaders. These secondary invaders may form in the areas of the body where the resident microflora was destroyed and this may cause harm to the body.

Certain microorganisms may flourish out of control, such as the yeast that is the cause of candidacies (Englekirk & Burton, 1979, p182).

The harmful and beneficial microflora must live together to provide a balance within the body. This is known as a symbiotic relationship. The symbionts (the organisms that live together) are two or more organisms of unlike species (Englekirk & Burton, 1979, p 183)

The balance may shift towards the pathogenic state if the body s defenses are vulnerable.

There are different types of symbiotic relationships. They are mutualism (both of the organisms need each other metabolically), communalism (the body is not harmed or benefited, but the microbe is benefited.), neutralism (organisms live in the same area but they do not affect one another) and parasitism (the microbe benefits at the expense of the body).

Englekirk & Burton (1979) describe microflora of the mouth as numerous and varied. The oral cavity provides shelter for many anaerobic and aerobic bacteria. The anaerobic microorganisms live in the gums, between the teeth, and on the surface of the tonsils. The excellent growing conditions in the mouth and throat provide for the difference and abundance of microflora. Most of the microflora found within the mouth are harmless; these include diphtheroids, lactobacilli, and mircococci. Yet if improper hygiene is practiced certain types of oral diseases may occur; such as tooth decay, gingivitis and peridondits. This disease start due to food that remains on and between the teeth which allows excellent growing conditions for many oral bacteria. These bacteria include Actinomyces, Lactobacillus, Streptococcus, Neisseria, and Villanelle.

According to Burton & Engelkirk (1992), there are helpful and damaging roles of resident microflora. There is also a connection between normal flora and the human host.

Englekirk & Burton (1992) state that there are four types of agreeing associations within the human body. The four types are mutualism, commensatism, neutralism, and parasitism.

Burton & Englekirk (1992) describe mutualism as when organisms are both beneficial and dependent on each other. Some mutualistic relationships have two organisms working together to produce a final result that could not be accomplished with out the aid of each organism.

Burton & Englekirk (1992) also describe communalism as when microorganisms have benefited but the host cells have not. Most normal flora has this relationship with its host.

Burton & Englekirk (1992) state that neutralism dwell only when organisms are in the same area, yet they do not affect one another. Many bacteria that lives within the mouth and inner body, and they do not affect one another.

Burton & Englekirk (1992) also describe parasitism as when an organism benefits at the expense of the host organism. This can be very damaging or fatal.

Part three

According to Englekirk & Burton (1979) viruses are very small and simple in structure. Viruses are distinguished from living cells because five properties. (1) They possess either DNA or RNA, never both; (2) their replication is directed by the viral nucleic acid within a host cell; (3) they do not divide by binary fission or mitosis; (4) they lack the genes and enzymes necessary for energy production; and (5) they depend on the ribosome s, enzymes and nutrients of the infected cells for protein production (Englekirk & Burton, 1979, p 65).

A virus molecule is made up of DNA or RNA and is surrounded by a protein coat that is known as a capsid. Some viruses have a shield made up of fats and polysaccharides that is known as a protective envelope. A virus must take over a host cell so that it may yield new virus particles, because, a virus does not produce protein synthesis because it does not contain ribosome s, nor does it produce energy because it does not contain sites for energy production.

A virus will replicate by injecting either its DNA or RNA into the host cell. When the genetic material from the virus takes over the metabolic machinery of the cell to produce viruses (Englekirk & Burton, 1979, p 67) After the virus has taken over the metabolic machinery of the host cell, it will disassemble the cells DNA and RNA and make viral DNA and RNA. The cell will then burst because the cell is full of virus particles, thus infecting neighboring cells.

Internal and external environmental conditions that can increase the spread of viral illness are heating; such as a fever, ultraviolet light, and certain types of chemicals.

Antibiotics are not recommended to fight off the spread of viruses because antibiotics are used to recognize foreign invaders of the body. A virus works by discussing itself as a normal cell within the body. The antibiotics, therefore, can not recognize the virus.

In this paper I have discussed the various definitions of bacteria, viruses, fungi, microbes and pirons. I have also described the role (beneficial and harmful) of micro flora in and on the body, and I have described the replication of viruses and its structure.

The study of microbiology is a very vast subject. Our whole life and existence relies on microbiology, and a better understanding of how it works for and against our world and bodies will only enhance our existence.







Burton, G. & Englekirk, P. (1992). Microbiology for the health sciences. Philadelphia: Lippincott.

Jenson, M. & Wright, D. (1989). Microbiology for the health sciences. New Jersey: Prentice Hall

Harley, B. & Klien, D. & Prescott, L. (1989). Microbiology.

England: W.C.B.Jenson & Wright (1992)

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