General Principles Of Microbiology.

ASSIGNMENT # 1: GENERAL PRINCIPLES OF MICROBIOLOGY

1. Describe the components of the bacterial cell envelope and the primary function of each.

The innermost layer of the bacteria cell envelope is the cell membrane. It is a typical phospholipid bilayer, as is found in animal cells. The primary function of the cell membrane is energy production and active transport. The next layer is the cell wall. It is made of N-acetyl glucosamine and N-acetyl muramic acid. Amino acids keep the cell wall together by forming cross-bridges. The primary function of the cell wall is to protect the bacteria from its environment. It also acts as an osmotic barrier and provides the shape of the bacteria. The outermost layer of the cell envelope is the outer membrane. The outer membrane contains lipopolysaccharides, which act as an endotoxin. However, only gram-negative bacteria cells contain the outer membrane. Also, found between the cell membrane and the cell wall is the periplasmic space. It is filled with periplasm, which is made of water and proteins. The proteins act in degradation, transport and motility.

(Source:http://www.microbiologytext.com/index.php?module=Book&func=displayarticle&art_id=59)

2. A 62 year old patient was diagnosed with shingles. This is termed a latent infection.

- What category of viruses causes latent infections?

DNA viruses cause latent infections. Retroviruses, such as HIV, also have the ability to become latent after reverse transcriptase enzyme creates DNA.

- There are some bacteria that also cause latent infections. With an example explain the difference between latent viruses and latent bacterial infections.

In latent viruses, such as herpes, the viral genome remains in the host cells, but not the infectious virons...

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8. Why is it important clinically to know the Gram stain and morphology of infecting bacteria?

Without completing the gram stain, it is very difficult to see the bacteria. The gram stain gives a few clues that narrow down what kind of bacteria this could be. First of all, the result of the gram stain (what colour it becomes), helps you identify whether it is a gram-negative or a gram-positive bacteria. The gram stain also allows you to see the shape of the bacteria. Both the staining characteristic and the shape help define which bacteria you are dealing with. Once this is known, it is much easier to treat. For example, there are very few gram-positive bacteria rods that infect humans. If this type of bacteria is found you have a very good idea about what the infection could be, and could use on of the antibiotics that work well on this type of bacteria.