LSM3232 Medicinal Microbiology Lab Report Essay

1989 Words Oct 12th, 2014 8 Pages
INTRODUCTION
Many infectious diseases caused by infectious agents, including bacteria, fungi, viruses and parasites, have plagued human existence CITATION Kon97 \l 1033 (Koneman, 1997). Thus the identification of bacteria becomes all the more important in the search for medicines and cure. Identification of bacteria is a multistep process because while some preliminary guesses can be made from the morphology of microbes on various differential agars, various other tests need to be done to differentiate and confirm their identity.
RESULTS
Bacteriology – When grown on MacConkey agar, A had abundant growth of pink punctiform colonies that are circular and moist. Microbes A are gram-negative cocci. B had moderate growth of yellow
…show more content…
Oxidation-fermentation (OF) tubes – OF test is important in differentiating members of the family Enterobacteriaceae, glucose fermenters, from the aerobic pseudomonads and similar gram-negative negative bacteria, because the latter are non-fermenters (Mahon et al., 2011). Glucose fermentation undergoes the glycolytic pathway, resulting in a colour change in the medium from yellow to green. C fermented glucose both in the absence and presence of air, resulting in yellow agar. E was only able to ferment glucose in the presence of air, so green agar was observed under anaerobic conditions.
Triple sugar iron tubes – This test is a used to determine if a gram-negative rod is a glucose-fermenter or not, in addition to testing if the microbe can ferment sucrose and/or lactose, gas production during glucose fermentation and H2S production – all of which are useful in differentiating gram-negative rods from the Enterobacteriaceae family (Mahon et al., 2011). Acid is produced when sugars are fermented, resulting in a drop in pH. Phenol red turns yellow once the pH drops below 6.8. Moreover, because of the slanted shape of the agar, microbes are exposed to anaerobic and aerobic environments in varying degrees.
Since only the butt of E is yellow while the slant is red, it can be deduced that E only ferments glucose such that the acid produced is not enough to turn the slant yellow. If the tube had been observed between the first 8-24 hours of

Related Documents