| dc.description.abstract | Escherichia coli (E.coli) hardiness, versatility, broad use and ease of handling have made it the
most intensively studied and best understood organism worldwide. However, research on
E.coli has primarily examined it as a model organism, one that is abstracted from any natural
history. It is a highly diverse organism with a complex, multi-faceted niche in the wild. Recent
studies of ‘wild’ E.coli has, for example, revealed a great deal about its presence in the
environment, its diversity and genomic evolution, as well as its role in the human micro biome
and disease. E.coli is the best indicator of bacteriological quality of water. This, coupled with
availability of affordable, fast, sensitive, specific and easier to perform detection methods,
makes water analysis simple. University of Embu dams are surrounded by various agricultural
practices and human habitats. Such occurrences could lead to contamination of surrounding
waters through surface run offs. This experiment intends to determine the comparative load of
E. coli between dams 3 and 5 of the University of Embu. Water was collected and tested using
the Most Probable Number (MPN). MPN is a method used to estimate the concentration of
viable microorganisms in a sample by serial dilution. It is commonly used in estimating
microbial populations in soils, water and agricultural products. MPN is most commonly applied
for quality testing of water i.e. to ensure whether the water is safe or not in terms of bacteria
present in it. A group of bacteria commonly referred as fecal coliforms act as an indicator for
fecal contamination of water. The presence of very few fecal coliform bacteria would indicate
that water probably contains no disease-causing organisms, while the presence of large
numbers of fecal coliforms would indicate a very high probability that the water could contain
disease-producing organisms making the water unsafe for consumption. Water being tested
was diluted serially and inoculated in MacConkey agar which is both a selective and
differential media. It contains bile salts and the dye crystal violet, which inhibit the growth of
gram-positive bacteria and select for gram-negative bacteria. It also contains the carbohydrate
lactose, which allows differentiation of gram-negative bacteria based on their ability to ferment
lactose. Organisms which ferment lactose produce acid end product which reacts with the pH
indicator neutral red, and produce a pink color. Both dams have high number of E.coli loads
though the greatest number was observed in dam 3.E.coli grows in a number of substrates like
skimmed milk ,xylose and cellulose and stains negative during gram staining due to the
presence of peptidoglycan in their cell wall. Regular water quality analysis should be done and
agricultural activities within water bodies avoided to reduce microbial runoffs and
contamination of water bodies. | en_US |
