Inoculating Needle Essay

To demonstrate the variation in growth of Serratia marcescens in different growth media. Hypothesis the growth of Serratia marcescens varies in different growth media.

Procedure

An inoculating needle was sterilized by placing it over a flame until it became red hot. It was allowed to cool for 20 seconds. The needle was used to pick a sample from a broth tube with Serratia marcescens. The needle with the sample was carefully placed on the nutrient agar slant and drawn lightly in a zigzag line. After this process, the inoculating needle was sterilized, allowed to cool and immersed in the broth tube to collect a sample of Serratia marcescens. The needle with the sample was inserted in a straight line into the nutrient agar deep tube and rapidly withdrawn along the path it was inserted. The needle was again sterilized, allowed to cool, and used to collect a sample from the broth tube. It was inserted into the nutrient broth tube and shaken softly to dislodge the microorganisms. After the process, the inoculating loop, as well as the necks of tubes, was flamed and their respective caps replaced.

Observation/Results

Turbid growth was observed in the nutrient broth. Similarly, an irregular growth was observed spreading from the point where the inoculating needle was placed. Unlike in the nutrient agar broth and nutrient agar slant, small traces of growth in nutrient agar deep were observed.

Conclusion

Oxygen contributed significantly to the growth of bacteria in the growth media. The tubes with enough supply of oxygen, nutrient agar broth and nutrient agar slant, experienced growth of Serratia marcescens whereas the tube with a little amount of oxygen, nutrient agar deep, did not experience the growth of Serratia marcescens (Ramaswamy and Marcotte 73).

Work Cited

Ramaswamy, Hosahali and Marcotte Michele. Food Processing: Principles and Applications.   New York: CRC Press, 2005. Print.