![]() Gather the YPD cultures of the parent strains to be propagated, a platinum inoculation loop, and an agar plate with fresh YPD media. The stock strains that you will use have been grown to a high density in liquid YPD medium. Your team will be assigned three different S.The third streak in each sector contains well-separated colonies that can be used for genetics experiments. Three streaks were used to spread the cells in each sector. Plate has been divided into three clearly labeled sectors. As you streak your strains, pay careful attention to detail to avoid cross-contamination or confusion about the identities of individual strains. (See the figure below.) The streak plates that you prepare will contain the stocks for future experiments. In our experiments, we will use a multi-streak protocol, which allows us to culture multiple strains on a single plate of culture medium. Is done with a freshly sterilized loop that picks up cells by crossing over the tracks of the previous streak, before beginning a new series of zig-zags. Because it may be difficult to resolve colonies from a single streak, many labs use a series of streaks on the same plate to separate colonies. Consequently, streaks appear thickest at their starting points, and the streak thickness decreases until it is possible to detect well-isolated single colonies near the end of the streak. The number of cells on the loop or toothpick decreases as the streak progresses. They then spread the culture by making a series of zig-zag strokes across the surface of the plate. Researchers begin a streak by picking up a small sample of yeast or another microorganism with a sterile instrument, which could be a platinum loop, a toothpick or micropipette tip. A streak plate is actually a serial dilution of an existing culture on solid media. Researchers commonly use streak plates to isolate single colonies. A colony, which has hundreds of millions of cells, is therefore a population of genetically very similar, but not completely identical, organisms. cerevisiae, with a genome of 12 Mbp, most cells will have accumulated at least one mutation by the time that they have undergone 9-10 divisions. Spontaneous mutations arise constantly in all cells, with a rate of approximately 10-8/base/ generation. A concern in all genetic experiments is unknown mutations that arise spontaneously and may affect the phenotype being studied. Microbiologists like to begin their experiments with a single colony, because the cells in a colony are the progeny of a single cell. Using the SFIC technique bacteria can be diluted until individual colonies are formed.\) Plates are particularly helpful in isolating a specific species of bacteria, which is not possible in a liquid medium. Can be made in Petri dishes of various sizes. PLATE: solid medium made with agar and various nutrients and indicators. Bacteria are inoculated into a broth+Durham tube using a loop. The tube is initially filled with the medium and then collects gas as the bacteria grow, creating a bubble. Durham tubes are used to detect the production of gases, such as CO2 or N2, by microorganisms. Bacteria are inoculated into a broth using a loop.īROTH+DURHAM TUBE: liquid medium made with various nutrients and indicators in which an upside-down smaller tube, called a Durham tube, is placed. Allows for the growth of large volumes of bacteria, the level of growth can be assessed based on the turbidity (cloudiness) of the culture. This type of culture is used for the growth of anaerobic bacteria which grow in the absence of oxygen and are inoculated by stabbing the media with a needle.īROTH: liquid medium made with various nutrients and indicators. Slant/deeps are inoculated by stabbing a needle into the butt and then immediately streaking across the surface of the slant.ĭEEP: solid medium made with agar and various nutrients and indicators. This type of culture medium gives the ability to grow bacteria in both an aerobic, oxygen-rich, environment (surface of the slant) and an anaerobic, oxygen deficient, environment (butt of slant). Similar to a slant but creates a deep zone, commonly called the ‘butt’. SLANT/DEEP: solid medium made with agar and various nutrients and indicators. Bacteria are inoculated onto a slant using a loop and grow in the surface of the agar. Multiple cultures are easily placed into test tube racks and stored under refrigeration. Agar slants are also useful in maintaining bacterial cultures, more so than stacks of Petri dishes. Slanting gives the bacteria a greater surface area on which to grow in a tube. SLANT: solid medium made with agar and various nutrients and indicators. ![]() \)ĭifferent Types Of Media For Bacterial Growth:
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