Scientific Lab - Research Paper Example

nown B: It was likely to be Salmonella Typhimurium bacteria which is a typical nonspore-forming rods, facultative anaerobic, motile and negative, They ferment glucose and utilize citrate as carbon source and are lactose and sucrose non fermenters. These tests have been fully explored in the next section. With regards to the aim of the experiment, which is to identify unknown bacteria from mixed culture #18 using biochemical and morphological test, the two organisms identified had distinct characteristics which were looked for following laboratory tests.

Normally, Gram staining is employed to differentiate 2 bacteria groups with different cell wall constituent. The method has the ability to differentiate Gram negative and Gram positive bacteria group; thus the bacterial cells are either colored red or violet. Gram positive bacteria is shown by Violet staining due to a thick layer of peptidoglycan existing in the cell wall of the bacteria, thus the crystal violet is retained by these cells on a slide. Consequently, Gram negative bacteria is shown by red staining due to a thin layer of peptidoglycan existing in the bacteria cell wall, hence crystal violet is not retained by bacterial cells.

(Winn et al,2006) MacConkey Agar is used to distinguish Gram- negative, lactose-fermenting organisms from organisms that are non-fermentative .It is an inhibitory and differential medium that contains Crystal violets, bile salts, inhibitory agent and neutral red. Neutral red acts as a pH indicator. Klebsiella pneumoniae bacteria is known to be lactose fermenters hence unknown A while Salmonella Typhimurium bacteria is not lactose fermentor thus unknown B. The orinithine decarboxylase test is important for Enterobacteriaceae differentiation.

(MacFaddin, 2000).  MR-VP broth for Methyl Red test consists of peptone, phosphate buffer and glucose. The unknown bacterium that is able to perform mixed-acid fermentation generates enough acid that overcame the broth buffering