The T-Streak Method

When trying to figure out the cellular morphology and arrangement the T-streak method is used to get isolated colonies from a sample of a bacteria. To begin the process a petri plate which has a layer of agar is divided into three sections in a T form. When preforming an experiment aseptic techniques are used between each step, therefore you flame the loop before and after every step. A sample is taken from a culture with an inoculated loop, then is spread in the top section of the plate in smooth slow action going left to right. Be sure not to press too hard to damage the agar. Flame the loop, then use a portion of the first section to drag the bacteria into the second division following the same technique but instead use the motion up and down. Finally, flame the loop, then drag a part of the …show more content…
It is a selective media because, it kills Gram positives but allows Gram negatives to survive. If there is growth present on the EMB media it means it is a Gram negative rod. The color of the results determine if lactose fermentation is present. If the sample is colorless then there is no lactose fermentation present. If the bacteria is purple then lactose fermentation is present. If the results have purple and green colors then the sample has great amounts of lactose fermentation. The lab manual explains “If a microorganism produces an enzyme called citrate permease, it will be capable of transporting citrate into the cell where it is converted into pyruvate and used as a carbon source” (Cooke 42). The result can vary between the agar turning blue or green. Blue means the results were positive for the bacteria to use citrate as a carbon source. Green means the results are negative and the citrate cannot be used for a carbon source. To test for the citrate utilization flame the loop, then take a sample of the bacteria and scrape it on the top of the Simmons-citrate