Bacteriology Laboratory Report

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Bacteriology Laboratory Report

By | November 2012
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Observing and Preventing Growth in Bacteria by Streak plates

By Max Livingston

Biology Lab 117
October 31, 2012

The streak plate technique that we used is to isolate/separate one bacterial colony or cell from another. Isolating colonies from one another is important, because characteristics like colony size, shape, and margins are only visible in isolated colonies. We obtained bacteria from our environment and used a cue tip to swab our bacteria on the luria broth agar plates. I then made hypotheses and predictions on how much bacteria growth would be in the specific samples collected and observed them through a microscope. Then we used paper disks (about 2cmradius) and dipped them into an antibiotic, antiseptic, and disinfectant. We then put the paper dipped disks in the bacterial lawn of our luria broth agar plates. We let the experiments sit for one week in order to draw proper conclusions of the zone of inhibition around the bacteria. After one week we observed that some bacteria had bigger zones of inhibition than others which means that some antimicrobial substances where more effective on certain bacteria.

“There are over 300 kinds of bacteria in our mouths, yet we can grow only a handful. Bacteria are everywhere, and they are very numerous.” (Finlay, 2000). Our group wanted to try to find the most bacteria riddled hot spots given our environment so we gathered bacteria with a swab from a local elevator button, the bottom of a water fountain, bottom of a toilet, and basic dirt. I then made hypotheses and predictions on the amount of bacteria that would be at these specific locations. I thought the hot spots for the bacteria would be the elevator button, bottom of toilet, and water fountain. “Few, if any, living organisms can survive under all possible environmental conditions on Earth.” (Dei, 2001).  In order to evaluate the effectiveness of various antibacterial agents, we needed to expose bacteria to the agent,...

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