What is the streak technique for bacteria?
In microbiology, streaking is a technique used to isolate a pure strain from a single species of microorganism, often bacteria. Samples can then be taken from the resulting colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested.
What are the steps of streak plate technique?
Procedure for Streaking a Plate for Isolation:
- Flame the loop and wire and streak a loopful of broth as at A in the diagram.
- Reflame the loop and cool it.
- Streak as at B to spread the original inoculum over more of the agar.
- Reflame the loop and cool it.
- Streak as at C.
- Reflame the loop and cool it.
- Streak as at D.
What is the streak plate technique used for?
The purpose of the streak plate is to obtain isolated colonies from an inoculum by creating areas of increasing dilution on a single plate. Isolated colonies represent a clone of cells, being derived from a single precursor cell.
What are the 3 main purposes for creating a streak plate?
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 are the different types of streaking technique?
Based on the pattern of streaking, the streak plate method can be classified into 4 types, viz.: Quadrant Streaking, T-Streaking, Continuous Streaking, and Radiant Streaking.
How do bacteria spread on agar plates?
One method of distributing bacteria evenly over the surface of an agar plate medium is commonly referred to as the spread plate method. Classically a small volume of a bacterial suspension is spread evenly over the agar surface using a sterile bent glass rod as the spreading device.
How many types of streaking plates are there in microbiology?
Many different streaking patterns can be used to separate individual bacterial cells on the agar surface. There are four basic types of streaking methods; Quadrant streaking.
What are the 3 categories of bacteria morphology?
The three basic bacterial shapes are coccus (spherical), bacillus (rod-shaped), and spiral (twisted), however pleomorphic bacteria can assume several shapes. What is this? Cocci (or coccus for a single cell) are round cells, sometimes slightly flattened when they are adjacent to one another.
What type of media is used for streak plate method?
With the streak-plate procedure, a mixture of cells is spread over the surface of a semi-solid, agar-based nutrient medium in a Petri dish such that fewer and fewer bacterial cells are deposited at widely separated points on the surface of the medium and, following incubation, develop into colonies.
What is streak plate test?
The streak plate technique is used to isolate the organisms (mostly bacteria) from a mixed population into a pure culture. The inoculum is streaked over the agar surface to “thin out” the bacteria. Some individual bacterial cells are separated and well-spaced from each other.
What unit is CFU?
colony forming unit
The colony forming unit (CFU) is a measure of viable colonogenic cell numbers in CFU/mL. These are an indication of the number of cells that remain viable enough to proliferate and form small colonies.
What are the types of streaking?
Types of Streak Plate Method
- Quadrant Streaking. It is the most commonly used and the most preferred method where four equal-sized sections of the agar plate are streaked.
- T-Streaking.
- Continuous Streaking.
- Radiant Streaking.
- Semi-quantitative Streaking.
- Zigzag Streaking.
- Quadrant Streaking Procedure.
- T-Streaking Procedure.
How many types of streaking methods in microbiology?
4 types
Based on the pattern of streaking, the streak plate method can be classified into 4 types, viz.: Quadrant Streaking, T-Streaking, Continuous Streaking, and Radiant Streaking.
How is CFU calculated?
To find out the number of CFU/ ml in the original sample, the number of colony forming units on the countable plate is multiplied by 1/FDF. This takes into account all of the dilution of the original sample. For the example above, the countable plate had 200 colonies, so there were 200 CFU, and the FDF was 1/4000.
How do you put bacteria on agar?
How To Grow Bacteria – YouTube
What are the 4 types of bacteria?
Bacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes).
What are the 4 common shapes of bacteria?
There are four common forms of bacteria-coccus,bacillus,spirillum and vibrio.
- Coccus form:- These are spherical bacteria.
- Bacillus form:- These are rod-shaped bacteria.
- Spirilla form:- These are spiral-shaped bacteria that occur singly.
- Vibrio form:- These are comma-shaped bacteria.
What characteristics does a good streak plate have?
Tips for the best results
Use only a small amount of inoculum. Streak lightly so that you do not gouge the agar. Flame the loop after you streak each quadrant. Make sure the surface of the plate is free of droplets of condensed moisture.
Why do we calculate CFU?
In microbiology, colony-forming unit (CFU, cfu or Cfu) is a unit which estimates the number of microbial cells (bacteria, fungi, viruses etc.) in a sample that are viable, able to multiply via binary fission under the controlled conditions.
How is CFU count calculated?
- To find out the number of CFU/ ml in the original sample, the number of colony forming units on the countable plate is multiplied by 1/FDF. This takes into account all of the dilution of the original sample.
- 200 CFU x 1/1/4000 = 200 CFU x 4000 = 800000 CFU/ml = 8 x 10.
- CFU/ml in the original sample.
How do you do a 4 quadrant streak?
How to properly streak a Petri plate for isolated colonies – YouTube
What is the difference between colony and CFU?
CFU stands for Colony Forming Units. What this means is the number of alive and active microorganisms in one serving of a probiotic dietary supplement. These are typically measured in CFUs per gram or per milliliter. A colony refers to the individual colonies of bacteria, yeast or mold growing together.
What is CFU per mL?
The final reported CFU per mL essentially represents the number of bacterial colonies observed on culture plates, multiplied by the level of dilution from the original sample to obtain a standard reporting of CFU per mL.
Why do we grow bacteria on agar?
Agar, which is a polysaccharide derived from red seaweed (Rhodophyceae) is preferred because it is an inert, non-nutritive substance. The agar provides a solid growth surface for the bacteria, upon which bacteria reproduce until the distinctive lumps of cells that we call colonies form.
How long can bacteria live on agar?
| Table 1. Approximate time bacterial cultures remain viable in different storage conditions. | ||
|---|---|---|
| Condition | Temp (°C) | Time (approx.) |
| Agar plates | 4 | 4 – 6 weeks |
| Stab cultures | 4 | 3 weeks – 1 year |
| Standard freezer | -20 | 1 – 3 years |