Microbiology Lab Report Example | Topics and Well Written Essays - 1500 words

Microbiology - Lab Report Example respectively. Introduction: Bacteria are ubiquitous in nature. They are beneficial and harmful to the human beings and animals. Bacteria are present in the food. Probiotics supplements contain specific strains of bacteria such as Lactobacillus and Bifidobacteria to increase the gut flora. Beneficial bacteria are present in the food and produce many important biological molecules. In the mozzarella cheese, Lactobacillus bulgaricus and Streptococcus thermophilus are present. Camembert cheese contains lactococcus and penicillium species are present. (Waites et al. 2009). Bacteria can be differentiated based on the enzymes secreted by them. Some enzymes are secreted out by the micro organisms enabling simple biochemical tests. The major exo enzymes present in bacteria are amylases, caseinase, gelatinase (hydrolytic enzymes), oxidase and catalase. (Gunasekaran 2007). Since most of the exoenzymes are hydrolytic enzymes which break down complex substances into simpler molecules, they are us ed as identifiers for the bacteria. (Sharma 2007). Catalase converts hydrogen peroxide into oxygen and water and oxidase oxidizes dichlorophenol indophenols from colorless to blue or red. (Benson 2001). The microorganisms present in the given samples can be isolated using the serial dilution technique and plated in the culture medium. The organisms are either gram positive or gram negative. The results obtained from the biochemical tests are used for the identification of the bacteria up to the genus level. (Reed et al. 2007). The number of bacteria present in the given sample is identified as the number of colony forming units. Colony forming units are then used to identify the number of bacteria present in the given diluted sample (Reed et al, 2007). The number of bacteria present in the given sample is calculated using the formula: Number of cells per gram = (Number of colonies (CFUs)) / (dilution x amount plated). The main objectives of this study are 1. Isolation of individual colonies from the given Probiotics, mozzarella cheese and camembert cheese samples. 2. Identification of the bacteria present in the given samples using the biochemical tests. Results: Table 1: food type and the morphological characteristics: Food type characteristics Probiotics 10-6 Circular, cream, raised and undulate Camembert 10-5 Pink, circular, convex and entire Camembert 10-4 Cream, punkiform , entire and convex Mozzarella 10-4 Brown, entire , circular Table 2: Colony count data Sample x10-3 x10-4 x10-5 x10-6 x10-7 probiotic - Greater than 300 Greater than 300 246 - Final count - 3 x 10^8 CFU / ml 3 x 10^9 CFU / ml 2.49 x 10^9 CFU / ml - Camembert 210 104 44 - - Final count 2.1 x 10^6 CFU /g 1.04 x 10^7 CFU / g 4.4 x 10^6 CFU / g - - Mozzarella 3 1 0 - - Final count 3 x 10^4 CFU / g 1x 10^5 CFU / g - - - Figure 1: The number of cells present in the given samples versus the dilution factor: Sample Colony characteristics Food characteristics Catalase Oxidase Gram stain String t est Agglutination Probiotics 10-6 Soured , acidic Circular, cream, raised and undulate x x Positive (blue colored rod shaped cells) v X ( no agglutination was formed ) Probiotics 10-5, Soured , acidic C