how to idenify bacteria after gram stain?

[Madiha Siddiqui]

hello!!
Im a student of Microbiology and im doing research on food microbiology,The topic is:Isolation of microorganisms from beef burger samples and raw fish.This is the topic of my final project.So, kindly help me. I have inoculated 3 plates of beef burger sample, EMB ,VRB and Nutrient agar.i want to identify that what type of bacteria have grown on these plates.kindly help me.what should i do after staining the colonies and observing them in microscope??I want to know that wether the bacteria is pseudomonas ,enterobacter etc.

[donnahardy2]

Hi Madiha,

The nutrient agar you are using is non-selective and will allow the growth of a wide variety of aerobic bacteria. The eosin methylene blue agar inhibits the growth of Gram-positive bacteria and has dyes that allow differentiation between bacteria like E. coli that ferment lactose, and other organisms like Pseudomonas, that do not. The violet red bile agar is similar to the EMB agar; it inhibits Gram-positive organisms, and differentiates between lactose and non-lactose fermenting Gram-negative bacteria.

Identification of all of the unknown bacteria in your samples would be a major undertaking. Flow charts such as the following help classify bacteria based on Gram Stain results, appearance of colonies on agar, and a variety of biochemical characteristics.

http://www.uiweb.uidaho.edu/micro_biolo ... charts.pdf

It seems to me that identifying all bacteria in the samples would be beyond the scope of a science fair project. Do you have access to a laboratory with the necessary facilities and reagents? If not, then perhaps it would be a good idea to think about the purpose of your project. Perhaps identifying coliform bacteria in the samples would be sufficient. What is the purpose of your project? What are you looking for? That information will help you decide how many bacteria you need to identify.

Donna Hardy