Streaking Technique and Isolating Pure Culture

Title: streaking technique and isolating pure culture

Objective

1) To understand the procedure of preparing a nutrient agar medium

2) To observe the physical appearance of microorganism that culture in a nutrient agar

3) To obtain single colony of microorganism

Introduction

In the field of microbiology, aseptic technique is a fundamental and important laboratory skill. A variety of procedures need the use of aseptic technique such as transferring cultures, inoculating media, isolation of pure cultures, and for performing microbiological tests. Proper aseptic technique prevents contamination of cultures from foreign bacteria inherent in the environment. Using proper aseptic technique can greatly minimize or even eliminate the risk of contamination. Isolation of a single species of microorganism from a mixed culture to obtain a pure culture is essential when applying aseptic technique.

Mueller-Hinton Agar is recognized by all experts as being the reference medium for the study of the susceptibility of bacteria to antibiotics and sulfamides. The medium can be used with complete confidence because it is rich in nutrients, able to grow fastidious organisms and cultivate microorganisms in large quantity. It is also recommended for testing most commonly encountered aerobic and facultative anaerobic bacteria.

According to Louis Pasteur, "Life would not long remain possible in the absence of microbes." A pure culture theoretically contains a single bacterial species. The most common method for isolation for a pure culture is to prepare a streak plate. The modern streak plate procedure has evolved from attempts by Robert Koch and other early microbiologists. The streak plate method is a way to physically separate the microbial population, and is done by spreading inoculate back and forth with an inoculating loop over the solid agar plate. Upon incubation, colonies will arise and single cells will have been isolated from the biomass.

To obtain a source...