Table of Contents
Why do we use spread plate?
The spread plate method is a technique to plate a liquid sample containing bacteria so that the bacteria are easy to count and isolate. A successful spread plate will have a countable number of isolated bacterial colonies evenly distributed on the plate.
How do you use a spreader in microbiology?
Drop cells or bacteria at the center of the dish. Researchers can then place the spreader on top of the dish and, without applying much pressure, swirl the spreader around on the dish to evenly distribute the cells or bacteria.
What is a streak plate used for?
Agar streak plates are an essential tool in microbiology. They allow bacteria and fungi to grow on a semi-solid surface to produce discrete colonies. These colonies can be used to help identify the organism, purify the strain free of contaminants, and produce a pure genetic clone.
What is pour plate method?
Pour plate method is usually the method of choice for counting the number of colony-forming bacteria present in a liquid specimen. Because the sample is mixed with the molten agar medium, a larger volume can be used than with the spread plate. Each colony represents a “colony-forming unit” (CFU).
How do you do a standard plate count?
The standard plate count method consists of diluting a sample with sterile saline or phosphate buffer diluent until the bacteria are dilute enough to count accurately. That is, the final plates in the series should have between 30 and 300 colonies.
Why is it important that the agar plates are incubated upside down?
Petri dishes need to be incubated upside-down to lessen contamination risks from airborne particles landing on them and to prevent the accumulation of water condensation that could disturb or compromise a culture.
Why are plates incubated upside down?
What is standard plate count in microbiology?
The Standard Plate Count (SPC) means the colony count of the mesophilic bacteria growing under aerobic condition on standard methods agar (Plate Count Agar), and SPC becomes the representative index indicating the degree of the microbial contamination of the food.
How do you calculate CFU?
Calculate the number of bacteria (CFU) per milliliter or gram of sample by dividing the number of colonies by the dilution factor The number of colonies per ml reported should reflect the precision of the method and should not include more than two significant figures.
What is the purpose of the spread plate technique?
Spread plate technique is a viable counting method employed to plate a liquid sample for the purpose of isolating or counting the bacteria present in that sample. A perfect spread plate technique will result in visible and isolated colonies of bacteria that are evenly distributed in the plate and are countable.
How do you spread liquid in a plate spreader?
Immediately move on to spreading the liquid; do not let it sit on the plate while you dispense other samples. Sterilize a plate spreader and touch it to the surface of the agar, away from the dispensed liquid, to cool. To spread the dispensed liquid around the plate, gently push the plate spreader back and forth.
How are cells deposited in a spread plate?
The principle behind this method is that when the Media plate is spun, at some stage, single cells will be deposited with the bent glass rod (Spreader) onto the surface of the Agar media.
What are the precautions for a spread plate?
PRECAUTIONS TO BE TAKEN….. ⇒ The protocol should be followed under all aseptic conditions preferably in Laminar Air Flow (Safety cabinet) to avoid any contamination. ⇒ Accurately measure the quantity while preparing the serial dilutions of the specimen.