Lab 3: Streak Plate, Culture Transfer Instruments and Techniques,

Isolation and Maintenance of Pure Culture

Introduction

Microorganisms are the foundation of life and it is critical for us to understand their behaviors as individuals versus a heterogeneous, mixed community, and cultivate supplementary. There are processes in order to ensure benign growth and maintenance of pure cultures. Such techniques to accomplish this task are through plate streaking with additional removal of a single colony to LB broth. Once you are able to successful isolated a colony from the pack, it’s crucial to provide a nutrient rich environment for the new colony to thrive in, at which you may store for later use.

Method and Materials

           In order to successfully preform this experiment, the immediate work space had to be sterile for safety purposes.  Using a 70% mixture of ethanol, students were to apply to their gloves and lab countertop.  Once the area is sterile, student were to use a streak technique with frozen E.coli cells on to a previously prepared LB broth petri dish. Student were to grab the non-sterile end of the toothpick and swirl the sterile side in the frozen stock of E.coli. Then gently create long dense streaks of the E.coli sample on about a third of the petri dish. After the initial streaks, students were to create more streaks on another third of the petri dish. Only this time, the toothpick was to overlap the initial streaks a couple times before continuing with more streaks. This task was repeated a third time, but the streaks were to have a bigger gap in between each streak. Allow for a bigger gap space enhances the possibility to isolate a span of colonies. When the streaking process was completed, the petri dishes would then be incubated at 37 degrees C, same temperature as the human gut.

                After 24 hours of incubation in LB broth, the E.coli cells became abundantly visible and allowed for student to select a lone colony. Using a sterile toothpick, the subject was appraised and extracted. The colony was then transferred to a sterile flask of new LB broth and again incubated at 37 degrees C for 24 hours.

Figure1: Me Creating a streak pattern

Figure2: Up close of creating a streak pattern

Figure3: More 

Figure4: professional material holder

Figure5: Sterilizing gloves

Figure6: Container of  semi-frozen E.coli

Results

         There were no quantitative results from this lab but qualitative instead. Student walked out of that lab with new knowledge on growing and maintaining pure cultures.

Discussion

         This lab was very eye opening in the real world applications and process for culturing pure samples. It was really awesome to get hands on experience with an array of techniques. Plus the essence of danger made the lab a little more exciting. Also, seeing that the class used our group’s petri dishes made the experience that much more exciting.  Cannot wait to see how my streak pattern came out.