Download I2323222007

Abstract
Bacteriophages are viruses that infect and lyse bacteria. They were discovered and described
twice, first in 1915 then in 1917. Bacteriophages are widely distributed in nature and have been
isolated from air, water, and soil food products. The abundance of phages in the aquatic
environment highlights their potential use for control of pathogenic bacteria in food and animal.
It's been known that most of the bacterial species have specific bacteriophages, and some
bacteria have even more than one type of phage infecting them. The main objective of this study
involved to investigate the bacterial host specificity of bacteriophages found in sewage effluents
with the specific aims being to isolate bacteriophage from the sewage, to observe the
bacteriophage effect on E. coli and Staphylococcus aureus and to find out the distribution of
bacteriophages in sewage effluents. 10 ml of the sewage-bacteriophage culture was centrifuged
and the supernatant which contained the bacteriophage was collected and mixed with overnight
bacterial cultures of Escherichia coli and Staphylococcus aureus. Incubation was done at 37°C
for 20 minutes for the phage to be adsorbed (attach) to the bacterium host. The contents of
cellphage tubes were poured semi-solid nutrient agar plates (molten, at 55°C), allowed to cool
and solidify for 20 minutes then incubated inverted, at 3rC overnight. Clear zones were spotted
on the lawn culture of both E. coli and S. aureus indicating lysis in both bacterial species. In both
species of bacteria it was clear that there was a significant decrease in the number of plaques
formed as the concentrations of sewage supernatant decreased. E.coli bacteriophage culture plate
1 found to have about 74% plaque dominance, decreasing to about 3% plaques in the plate with
the highest dilution. S.aureus culture plate A was found to have about 0.8% plaque dominance,
decreasing to about 0.2% plaques in the plate B. Reasons for inconsistent results could have
arisen from errors in the dilution process and influence of the assay. There still is so much left
undone and this is a wake up call for Microbiologists around the globe to delve into this area that
still remains largely unexploited but seemingly with a lot of potential.
Key words: Bacteriophages, plaque, Escherichia coli, lysis, Staphylococcus aureus