Question

Background

Bacteria in the environment must be controlled to reduce the chance of spreading the bacteria and possible infectious disease. There are many methods of controlling bacterial numbers; heat, chemicals, drugs and radiation are a few. Each control method targets something within the cell either structurally or metabolically that leads to cellular death. Microbes are most vulnerable during the exponential growth phase, when there is a high level of metabolism and cellular structures are being created. Many control methods reduce the number of microbes and others are designed to completely eliminate all forms of microbes. A common method to determine the effectiveness of a chemical or drug is called the Kirby Bauer disc test. For this test, small disks of paper impregnated with different concentrations and different types of antibiotics or chemicals are placed on a lawn of bacteria on an agar plate. The antibiotic or chemical then diffuses through the agar over time. Susceptibility of the bacteria to that chemical is determined by measuring the zone of inhibition, or lack of bacterial growth, surrounding each disk. Basically, the bigger the zone of no bacterial growth the more susceptible the microbe is to that specific chemical. In addition, any resistant bacteria will appear as colonies within the zone of inhibition. This laboratory exercise will investigate the effectiveness of using chemicals to control bacterial growth

Questions

Answer 1

1. The chemicals which were most effective are :-

- Alcohol

- Household cleaner

- Control

Because there were lack of bacterial growth surrounding each disc containing these chemicals.

2. The chemicals which were least effective are :-

- Hydrogen peroxide

- Bleach

Because there were presence of bacterial growth surrounding the disc containing these chemicals .

3.No,it is a not fair test as it is checked practically that whether there is a bacterial growth surrounding the disc or not using ecah chemical ,but particular to a type of bacterial only . Its possible that hydrogen peroxide and bleach restricts or inhibit the growth of other bacteria and viruses. I won't determine these chemicals as antimicrobial as these chemicals should be analysed for other types of bacteria too.

4. The purpose of control group is to assess or compare the cause and effect relation with experimental group. The control groups are not provided any intervention , experimental group is provided the intervention .