Unknown Bacteria Lab Report

The purpose of this lab report is to employ a myriad of skills, tools and, methods learned throughout this semester to perform the appropriate tests for the identification of the assigned unknown bacteria. Add more background information here!!! The most important tools and techniques used during this identification include aseptic technique, microscopic examination and, the use of selective and differential media.

Aseptic technique is an important tool for microbiologists. It is imperative that aseptic technique is maintained throughout the length of any test to avoid any cross-contamination that may lead to inaccurate results. This method requires the use of a micro incinerator to sterilize any tool that may encounter the bacteria, along

Differential media allows for the differentiation between two similar micro-organisms through how the bacteria may handle certain compounds found in the media or the different reactions that may take place when the bacteria is exposed to the medium (3). Selective media on the other hand allow only certain microbes to grow. This is due to the plate containing a limited amount of nutrients, compounds and chemicals that will deter the growth of certain bacteria (3). Dyes, antimicrobial substances, salts, certain growth inhibitors and, antibiotics are also found on this type of medium (3). The differential and selective media mentioned in this lab are as follows: Mannitol Salt Agar (MSA) plate, MacConkey agar (MC) plate, Eosin Methylene Blue agar (EMB), and Hektoen Enteric Agar (HEA) (3). The MacConkey agar plate and the Mannitol Salt agar plate are both used in the identification of the unknown. The MC plate is a selective and differential medium. It is considered a selective medium because the bile salts and crystal violet aspect of the medium prevent the growth of gram positive bacteria (3). This medium is differential because of the lactose and neutral red. Neutral red acts as a pH indicator, it remains colorless when the pH is above 6.8 and becomes red when the pH falls lower than 6.8 (3). The gram-negative coliform type bacteria would turn this medium red, while bacteria that do not ferment lactose will not incur a color change. The MSA plate is also considered a selective and differential medium. MacConkey is commonly used to differentiate between different species in the Enterobacteriaceae family. MSA is considered selective because it contains 7.5% NaCl and only bacteria that can survive the high osmotic pressure due to the sodium chloride will be able to grow on this plate. This medium is considered differential because of mannitol and phenol red. Mannitol is a sugar alcohol