Why is the 16S rRNA gene a preferred marker for the identifi

Why is the 16S rRNA gene a preferred marker for the identification, classification, and evolutionary history of microbes? Detail your answer based on 5 main characteristics of this gene. In other words, for each of the 5 characteristics listed, provide a reason for why that is important to make this gene a preferred one for this type of study. Lastly, are “functional” genes, such as antibiotic resistant genes not appropriate to study evolutionary history of microbes?

the 5 things may include, its availability, its length, and its conserved and variable regions, and it being acquired by vertical transfer. im hoping for this to be explained in a little more detail because i dont really get the veritcal transder part of the bp (length) part.

thanks

Solution

Several aspects of the 16S rRNA gene make it a preferred marker for the identification, classification, and evolutionary history of microbes. Firstly, because it is widespread among prokaryotes. Secondly, it\'s size (1,550 bp long) and the high degree of functional conservation. It is large enough to provide statistically valid measurements. The clock-like mutation rates throughout prokaryotic evolution are the result of it’s high degree of functional conservation. The Third aspect of the16S rRNA gene is that it is composed of both variable and conserved regions. The conserved regions can be used for designing amplification primers across taxa whereas, the nine hypervariable regions (V1-V9) can be effectively used for the comparative taxonomy. Lastly, it is the most common gene to be used for constructing phylogenetic relationships in prokaryotes as it is acquired by vertical transfer. It is universal in bacteria so relationships can be measured among all bacteria but recently it has been argued that 16s rRNA genes can also be transferred by horizontal gene transfer. It is important to make this gene a preferred one for this type of study because 16S rRNA gene sequences analysis allow better, accurate, robust and reproducible bacterial identification than that obtained by phenotypic testing. The phenotypic test results are less subjective. It can identify poorly described, rarely isolated, aberrant strains, and can also recognize novel pathogens. “Functional” genes, such as antibiotic resistant genes are considered inappropriate to study the evolutionary history of microbes because it is generally acquired by horizontal or lateral gene transfer. Many bacteria become resistant by acquiring genes via horizontal gene transfer. Such genes in the organism may show different rates of evolution or even show different evolutionary history. Often Evolutionists point out the development of antibiotic resistance by bacteria as a validation of evolutionary change but molecular analysis of the genetic events that lead to antibiotic resistance do not support this assumption.