Viruses & Bacteria

Topics: Bacteria, DNA, Virus Pages: 5 (1009 words) Published: October 2, 2014


Viruses
&
Bacteria
Title: Kirby-Bauer Method of Antibiotic Effectiveness
Purpose: The purpose of this lab was to determine the effectiveness of certain antibiotics and determine their zone of inhibition Data:
Name of Antibiotic
Zone of inhibition (mm)
Effectiveness
Streptomycin
15mm
Sensitive
Chloramphenicol
29mm
Sensitive
Novobiocin
20mm
Intermediate
Neomycin
13.5mm
Intermediate
Tetracycline
22mm
Sensitive

Analysis:
1. Which antibiotic was the most effective? The most effective antibiotic was Chloramphenicol. Chloramphenicol is used against serious infections such as typhoid fever. This antibiotic produced a zone of inhibition of 29 millimeters. This demonstrates that chloramphenicol is the most effective antibiotic because the bacteria were the most sensitive to it. 2. Will the most effective antibiotic work well for all types of bacteria? Why or why not? Chloramphenicol will not necessarily work well with all types of bacteria. There are millions of bacteria and each has a different characteristic and serves a different purpose. Many bacteria overtime become resistant to the antibiotic and multiply. For example, pseudomonas putida KT2440 is a chloramphenicol-resistant bacterium that is able to grow in the presence of this antibiotic at a concentration of up to 25ml. 3. What are three aseptic techniques you used in this lab activity? Aseptic technique is a procedure used by medical staff to prevent the spread of infection. The goal is to reach an environment that is free of harmful microorganisms. In the lab activity, examples of aseptic techniques used include sterilizing your work area (before and after), “dipping and flaming” the inoculating loop (after every use), and using a sterile disc to add to the center of the plate. 4. Give two reasons why we are seeing an increase in antibiotic resistant bacteria. The dramatic increase in antibiotic resistant bacteria is a result of evolution. Once an antibiotic is used against a bacterium, it in time evolves through the process of natural selection. Another reason why there is an increase is antibiotic resistant bacteria is the spontaneous mutation in the bacterium’s DNA. Many antibiotics work by disabling a bacterial protein, but in some cases genetic change can remove that protein. As more bacterium become resistant to an antibiotic, it transfers it’s resistant genes to other bacterium 5. Do antibiotics work for viruses? Antibiotics don not work against infections caused by viruses. All colds and most coughs and sore throats are caused by viruses but these will get better on their own. Antibiotics do not work on viruses because viruses do not have organelles or metabolism and they do not produce on their own. This means they are not living things. A virus reproduces by injecting its DNA into a host cell. The host cell replicates the DNA and makes new viruses.

History of Viruses
A virus is an infectious particle made only of a strand of DNA or RNA surrounded by a protein coat. It is non-living! It can only exist within a “host,” it has no cellular structure, and it has no cytoplasm, organelles, or phospholipid membranes. No one knows really where viruses originated, but the concept of a virus as a distinct entity dates back to the late 1800s. A virus can spread from someone coughing or sneezing, or it can be transmitted through physical contact such as shaking hands. Once a virus is within your body, it finds a host cell and attach to it. Its base plate locks onto the cell and the virus begins to release its nucleic acid (DNA/RNA). Once the DNA/RNA is in the cell, the cell is tricked into making copies of the DNA or RNA. New viruses now begin to form and leave the cell to attach to a new host. The cell will then burst. Though, when our immune system recognizes the virus, it attacks and destroys it and our body will eventually get better. So, even though the viruses are rapidly replicating, our immune system destroys them at an...
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