Antimicrobial Soil Isolates

Topics: Bacteria, Microorganism, Microbiology Pages: 8 (2612 words) Published: April 17, 2005
Project 1: Antimicrobial Activity of Soil Isolates

John Franklin Farrar

Department of Biology and Microbiology and Biology
Address BOX 22750 BOWEN HALL, RALEIGH, NC, 27607

Isolation and characterization of microorganisms is a practice that aids in
Increasing ones knowledge of a laboratory setting and it helps improve on
Using sterile technique. Isolates of soil microbes can be categorized and
Characterized based on a number of criteria ranging from gram-staining
Which is done for this project to enumeration which is quantitative description
Based on the amount of microbial colonies available. The Antimicrobial
Activity of three different microbes were also tested and results were obtained
For two out of three of the microbes. Two out of three of the tested microbes
Exhibited antimicrobial activity towards the bacteria E. Coli and B. Mycoides
And the results were recorded. Microbes produce various antibiotics and by
Isolating different microbes the antibodies can be tested for. Introduction:
This lab focuses on the isolation and characterization of an unknown organisms expressing interesting properties in relation to Antimicrobial Activity. At the conclusion of this laboratory experience The researcher would be required to describe the isolates obtained from the soil macroscopic and microscopic appearance, Perform the gram stain of the microorganisms in question and to discriminate the organisms from other microbes that could be contained in the soil and to finally make certain that the organisms have not been exposed to outside sources and be isolated in a pure culture. The researcher must first isolate the microbe and try to grow the organism in a pure culture to commence with testing the organism. The isolation of Microbes in a laboratory and clinical settings are of the up most importance and due to the isolation of different microbes from each other various procedures become open for the researcher to use like six fold dilutions that allow for the quarantined microbe to be reduced down in number to ensure that the test are being run are being tested on just a single type of organism. But before dilutions can occur the microbe must first be liberated from the soil and streaked onto an Agar plate to grow. There are various methods that can be used once the organism has grown onto the agar plate to ensure that the sample collected would only contain one pure organism. Streak plate enumerations also occur once the isolation of a particular microbe has occurred and the data that is received if the amount of organisms on the plate are between 30-300 individual colonies can be used because these are accepted values for Cell plate enumerations. After initial isolation a variety of techniques can be implemented to analyze and characterize the various microorganisms. The Gram Stain is a procedure that is performed in order to determine the difference between two main microbial cell wall types. Gram-positive cells have a cell wall made up mostly of a thick, peptidylglycan layer. These cells retain thecrystal violet color and the acetone alcohol acts as a dehydrating agent causing all peptidoglycan pores toclose and preventing the insoluble Crystal violet-Grams iodine complex from decolorizing. These cells appear PURPLE. Gram-negative cells losetheCrystal violet-Gram's iodine complex easily because the acetone-alcohol cannot seal the thin peptidylglycan layer to stop the decolorization. These cells lose the complex, but take up the lipid soluble counterstain, Safranin. These cells appear RED/PINK(laboratory Manual). Observing the types of antibiotics that an organism produces is a tool which could help classify and identify a microorganism also. In contrast to the just mentioned point with the aid of antibacterial disk a researcher could identify what antibiotics hinder the growth of the bacteria could help identify the microorganism. Each of these methods may...

References: -Microbiology Laboratory Manual
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