Biological Questions

The methylene no-count in the medium inhibits the growth of Gram-positive bacterium. The mechanism by which the prohibition era works is not well- belowstood, but small amounts of methylene blue successfully inhibit the growth of most Gram-positive bacteria. The colour eosin responds to changes in pH, changing from colorless to black under acidic conditions. EMB- agar-agar medium contains both lactose and sucrose as energy sources, but no glucose. Lactose-fermenting bacteria, which are generally enteral bacteria, such as Escherichia coli, Klebsiella, and Enterobacter acidify the medium, and the colonies appear black with a greenish sheen. Colonies which do not ferment lactose, such as Salmvirtuosolla, Shigella, and Pseudomonas appear translucent or pink.

Vogel-Johnson agar nookie be used to selectively grow coagulase-positive, mannitol-positive Staphylococcus aureus from clinical specimens and foods (Biol, 2004). Triple sugar press agar is a derived function medium for differentiating between different intestinal bacteria (lactose and non-lactose fermenting).

numerous different biochemical reactions toilette be measured in growth media to identify organisms (Growth, 2004). Tests can measure the presence or absence of enzymes involved in catabolism of substrates added to differential media. The hullabaloo of sugars can be identified by incorporating pH indicators in the medium, as in EMB-agar. The production of hydrogen spatter and/or carbon dioxide during sugar fermentation can be assay

Little is currently cognise some how biocides are taken up into bacterial cells (Russell, 2002, 599). Targeted drug lecture may be the only way to get biocides into bacteria cells effectively. More study is needed urgently because the current manner of avoiding resistance problems in hospitals is to rotate the use of disinfectants, replacing one with another which acts in a different way. Until more is known about how biocides act on bacterial cells, effective disinfectants pass on not be found.

Qu. 3.

Gram-negative bacteria appear to be more resistant to biocides than Gram-positive bacteria because of the impermeability of their outer(a) membranes or cell walls (Russell, 2002, 599). Efflux systems may also be responsible for removing toxic drugs and molecules of biocide from the cells. Biocides are used mainly for international purpose at concentrations much higher than the minimum bactericidal concentrations of antibiotics, and such concentrations are unlikely to be effluxed from cells. However, "low remnant concentrations could act could act as a focus for pick of organisms containing efflux genes or for the rapid or gradual using of biocide-resistant bacteria" (599).

Biol 207 Microbiology. (2004). Retrieved at:

ed by using gas collection vials or can be measured in agar. Hydrogen sulfide production by bacteria can be identified by observing growth in a medium containing ferric iron. If sulfide is produced, ferric iron complexes with H2S and forms a black precipitate of iron sulfide. The utilization of citric acid by bacteria causes a pH pinch and the incorporation of a dye in the medium causes a color change to occur which identifies the presence of these bacteria. Xylose lysine deoxycholate agar is a differential medium for the isolation of gram-negative enteric patho
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