Petri Dish Lab Report

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In microbiology, bacterial identification relies on isolating individual bacterial colonies of different species. The streaking for isolation technique is a tool used to obtaining a pure culture. The technique consists of taking an original inoculum that contains a mixed culture and spreading the bacteria into four quadrants on a solid medium. The purpose of spreading the mixed culture on a petri dish is to reduce the number of bacteria in each subsequent quadrant to one parent cell of each type of bacteria. One isolated bacterial is called a colony; which consist of thousands or even millions of individual replicates of the original parent cell with the same DNA. Identification of these parent cell will be isolated further into individual bacterial colonies used in subculturing. …show more content…

One type of bacteria from the mixed culture plate is placed on a separate plate of media for testing. That one parent cell will multiply itself through a process called binary fission producing bacteria with the same DNA. The pure culture will be used for further study of the bacteria. The unknown species KK appeared to contain a pure culture because all of the colonies on the petri dish were similar in color and shape after incubation.

Gram stain is one of the most important stains in determine the morphology and cell wall composition of the bacteria. The stain is positively charged and is attracted to the negatively charged surface of the bacteria; which produces the purple or red color of the gram stain. The gram stain results of unknown KK revealed that the bacteria species were gram-negative, red/pink, and rod shaped. Therefore, a MacConkey agar test will be conducted in order to differentiate two classes of gram negative

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