What are the types of streaking techniques in microbiology?

There are 4 types of streaking techniques in microbiology. They are differentiated based on the pattern of streaking. The 4 types of streaking techniques include: 

1. Quadrant Streaking: This method involves sequentially streaking 4 equal-sized sections of the agar plate. The first quadrant, which is the section that’s streaked first, has the highest inoculum concentration. The second, third, and fourth quadrants have successively lower concentrations of the inoculum. The fourth quadrant, which is highly diluted, results in isolated colonies following the incubation. Only one specimen can be used per 10cm plate with this streaking technique.   
2. T-Streaking: In the T-streaking technique, the agar Petri plate is divided into 3 sections by drawing the letter T. Each adjacent section is sequentially streaked with the final section diluted to the point of giving rise to isolated colonies following incubation.  This streaking method can be used to culture only one sample in a single 10 cm plate. 
3. Continuous Streaking: This is a quick and easy streaking technique in which an inoculum is evenly distributed from the starting point of the plate to the plate’s center in one single continuous movement. This method can be used only if the inoculum is very diluted. 
4. Radiant Streaking: In the radiant streaking method, the inoculum is streaked at one edge first. It is then spread above the edge in vertical lines, which are later cross streaked diagonally. This technique is suitable for propagating pure culture. It is also suitable for use in case of a dilute specimen. 

Modified forms of streaking include: 

1. Semi-quantitative Streaking – In this modified form of continuous streaking, a certain volume of the liquid specimen that is caught in a calibrated loop, is streaked in a horizontal line in the middle of the Petri plate. A single continuous back and forth movement is used to spread the specimen all over the plate. Semi-quantitative streaking enables researchers to obtain a pure culture and estimate the viable load in a single go. 
2. Zigzag Streaking: Another form of continuous streaking, this technique involves streaking a loopful of the specimen all over the Petri plate in a single continuous zigzag pattern.  It is widely used for propagating the pure culture and culturing it in larger quantities.