Isolation essay

The isolation of independent bacterial species from various environmental sources is important in all ranches of microbiology since bacteria are ubiquitous and live in microbial communities of mixed populations. Populations in microbial communities or ecosystems may interact and cooperate in their efforts to obtain nutrients from the environment with the waste products from one group Of microorganisms serving as nutrients for another. Alternatively, the metabolic wastes from fermentation processes of some bacteria in a population (for example acid production) may provide a favorable ecological niche for bacteria that prefer to grow at low PH.This exercise is designed to teach you owe to use solid media and streak plate techniques to isolate pure bacterial colonies from a mixed population of bacteria.

The instructor will provide TTS plates (Tropic Soy Broth mixed with 15% agar, heated to sterilize media and melt agar then poured into a Petri dish) and a culture containing Escherichia coli and/or Bacillus subsists and/or Staphylococcus erasures and/or Seriate mercenaries. Isolation of bacteria using the streak plate technique: Label the bottom of a Petri dish (side containing the agar) (Why? ) with your initials, date and lab section.Your instructor will provide you with a test tube intonating two or more bacterial species. Mix the contents in the test tube by gently shaking the test tube.

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This will ensure that all of the bacteria are in suspension. Aseptically remove some of the culture from the test tube with a sterile cotton tipped applicator. Your instructor will demonstrate this before you start your exercise. Aseptically transfer the contents of the applicator to a small section of the plate (approve. 10% of total plate surface area) as shown by your instructor and in the diagram below. (The cover of the Petri dish must never come in contact with the laboratory bench)Flame your inoculating loop and allow the loop to cool in the air or by dipping the loop in a sterile section Of the media.

Turn the plate 90 degrees and sample some of the bacteria from the initial streak and drag the loop across the surface of the bacteria in a gig-gag fashion. Make certain that you never re-gig over a gag. Also make certain that you do not enter the previous sector more than twice. (WHY? ) Turn the plate another 90 degrees and sample some of the bacteria from the second streak and isolate as above. Third streak as above. Incubate the plates upside down (WHY? Or 24 hours at CHIC for 24 to 48 hours, remove and refrigerate plates. Observe the plates for individual colonies during the next lab section.

Observation of individual colonies: In terms of colony characteristics, morphology, size, opacity and color completely describe the bacterial colonies that you have isolated. (See page 3. ) Escherichia coli Staphylococcus erasures Bacillus subsists Seriate mergansers Second Lab Period Analysis of bacterial colony characteristics: Bacteria have different colony morphologies and characteristics that are specific to the menus and species Of the organism.Colonies can be classified by size, form, elevation, margins, color, texture, and opacity. With respect to opacity one can identify a given colony as opaque (cannot see through the colony), translucent (can see through the colony but cannot clearly see objects through that colony) or transparent (can see through the colony and can clearly see objects through that colony as if looking through glass). For example Bacillus subsists produces colonies that are large with irregular borders, slightly raised with undulate margins, off white.

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