Saran's Learn Microbiology

STREAK PLATE TECHNIQUE AIM         To isolate the pure strains of bacteria by Streak plate technique (Quadrant streaking method). PRINCIPLE              The Streak plate technique is a rapid qualitative isolation method used for the isolation of a pure culture of the bacteria from the mixed population.  Streaking method was first developed by Loeffler and Gaffky in Robert Koch’s laboratory, which involves the dilution of bacteria by systematically streaking them over the exterior of the agar in a Petridish to obtain isolated colonies which will then grow into the number of cells or isolated colonies. The inoculum is streaked over the agar surface in such a way that it “thins out” the bacteria. Some individual bacterial cells are separated and well-spaced from each other. Aseptic techniques are used to maintain microbiological cultures and to prevent contamination of the...

  DIFFERENCE BETWEEN SPREAD PLATE METHOD AND POUR PLATE METHOD Features Spread plate method Pour plate method Definition A technique used to count or isolate bacterial colonies on the surface of the agar. A plate prepared by mixing the inoculum with the cooled but still molten medium before pouring the latter into the Petri dish. Preparation Inoculum is spread on the solidified agar on a plate by a spreader. Molten agar is poured on the inoculum in a Petri dish and gently swirled. Amount of Inoculum 0.1 ml 1 ml Use of Glass L - Rod Uses a Glass L – Rod  to spread the sample evenly on the surface. Not used. Colony growth Only on the surface of the medium. In and on the medium. Area of Growth Less area to grow. More area to grow. Purpose ...

POUR PLATE TECHNIQUE AIM           To isolate and enumerate the bacteria present in Soil sample by Pour plate method. PRINCIPLE                Pour plate technique is the method of choice for counting the number of bacteria present in a sample.  In this method, fixed amount of inoculum (generally 1 ml) from a sample is placed in the center of sterile Petridish using a sterile pipette. Sterile Nutrient agar (approximately 20 ml) is then poured into the Petridish containing the inoculum and mixed well.  After the solidification of the Nutrient agar, the plate is inverted and incubated at 37 °C for 24 hours. Microorganisms will grow both on the surface and within the medium. Colonies that grow within the medium generally are small in size and may be confluent; the few that grow on the agar surface are of the same size and appearance as those on a streak plate. Each (both larg...

SPREAD PLATE TECHNIQUE AIM            To isolate and enumerate the bacteria present in Water sample by Spread plate method. PRINCIPLE              Spread plate technique is the method of isolation and enumeration of microorganisms in a mixed culture and distributing it evenly. The technique makes it easier to quantify bacteria in various samples. A perfect spread plate technique will results visible and isolated colonies of bacteria that are evenly distributed in the plate and are countable. The technique is most commonly applied for microbial testing of foods or any other samples and to isolate and identify variety of microbial flora present in the environmental samples e.g., water and soil. MATERIALS REQUIRED Water sample Erlenmeyer flask Pipettes Test tubes Glass L – rod Distilled water Nutrient agar plates Incubator PROCEDURE I.  Serial Dilution Technique a)      Prepare a series of ...

GERM TUBE TEST AIM        To identify and differentiate Candida albicans from other Yeasts by Germ Tube Test or Reynold’s Brande Phenomena. PRINCIPLE         Germ Tube Test is the Confirmatory test which is used to differentiate  Candida albicans  from other yeast. Germ tube formation was first reported by Reynolds and Braude in 1956 so it is also called as Reynold’s - Brande Phenomenon. Germ tubes are short outgrowth, non-septate germinating hyphae. They are half the width and 3 – 4 times the length of the cell from which they arise. When Candida albicans is grown in human or sheep serum at 37 °C for 3 hrs, they forms a Germ tubes, which can be detected with a Wet films as filamentous outgrowth extending from yeast cells. It is positive for  Candida albicans  and  Candida dubliniensis (produce Germ tube after 3 hrs) .  Approximately 95 – 97 % of  Candida albicans  isolated develop Germ tub...

SLIDE CULTURE TECHNIQUE AIM        To identify the Fungi morphology without any disturbance by Slide culture technique. PRINCIPLE       Fungi are the group of Eukaryotic microorganisms and they are identified mostly by close examination of its morphology and the characteristics it possess. Identification of Fungi is often difficult by tease mount method because of the dislodgement of conidia and spores from the Conidiogenous cell. To overcome this, Slide cultures technique is considered best for preserving and observing the actual structure of a fungus without any disturbances. The method was first developed by Riddel in 1950 and currently, several modifications are in use.      In Slide cultures technique, fungi are inoculated in small blocks of Nutrient deficient agar medium (Cornmeal agar or Potato dextrose agar) (Fungi when grown in nutrition deficient medium develop spores rapidly and adhere to th...