Handbook of 16S rDNA Sequencing: The Past and the Present

Posted by beauty33 on November 2nd, 2018

The basic concept of 16S rDNA

16S rDNA is one of most useful and most commonly used molecular clocks in the systematic classification of bacteria. It has few species but large content (about 80% of bacterial RNA content). Its molecular size is moderate and exists in all organisms. Its evolution has been smooth and is highly conservative in structure and function. It is known as "bacterial fossil". In most prokaryotes, rDNA has multiple copies, and the copy number of 5S, 16S, and 23S rDNA is the same. 16S rDNA is moderately sized, about 1.5Kb, which can reflect the differences between various strains, and can be easily obtained by sequencing technology, so it is widely accepted by bacteriologists and taxonomists. In short, 16S rDNA is universal, conservative, moderately sized and has variable zone.

To be more specific, this article summarizes its features as follows:

1. 16S rRNA is ubiquitous in prokaryotes. rRNA is involved in the process of protein synthesis. Its function is essential to any organism, and it remains unchanged during the long course of biological evolution. It can be seen as a time clock for biological evolution.

2. In 16S rRNA molecule, it contains both highly conserved sequence regions and moderately conserved and highly variable sequence regions, so it is suitable for the study of various biological phylogenetic relationships with different evolutionary distances.

3. The relative molecular weight of 16S rRNA is moderate, about 1540 nucleotides, which is convenient for sequence analysis.

4. The variable region sequence varies from bacteria to bacteria, and the constant region sequence is basically conserved. Therefore, primers can be designed by using the constant region sequence to amplify the 16S rDNA fragment, and the difference between the variable region sequences can be used for different genus and strains. Based on this, the bacteria were classified and identified.

16S structure

The 16S rRNA gene sequence includes 9 variable regions and 10 conserved regions. The conserved region sequence reflects the genetic relationship between species, while the variable region sequence reflects the differences between species.

Figure 1. 16S rRNA gene sequence

About author:

As a leading provider of NGS services and a partner of Illumina, CD Genomics offers a portfolio of solutions for metagenomics sequencing. 16S/18S/ITS amplicon sequencing is characterized by cost-efficiency, high-speed and practicability to help you identify and investigate the microbial community. With over 10 years of experience, we can totally meet your project requirements and budgets in the exploration of microbial biodiversity.