Breakthrough in classification of new bacteria

Researchers in Germany looked at the minimum standards used to compare the genetic material of new bacteria to well-known types and found that increasing the threshold for one genomic test could remove the need to carry out a second, more difficult test.

“Describing new bacterial species is a highly demanding process,” says Professor Erko Stackebrandt of the German Collection of Micro-organisms and Cell Cultures in Braunschweig, Germany. “It involves a broad range of tests set by international committees and only a few labs have access to all of the methods needed.”

Two of these standard tests look specifically at the genome of an organism and compare it to that of other known bacteria. It is these genomic tests that Professor Stackebrandt and his colleagues concentrated on to help speed up the process of identifying new species.

To study how different bacteria relate to each other, microbiologists use 16S rRNA gene analysis. This can be helped by using an additional technique called DNA-DNA hybridisation to show how closely related two species are.

“We found that by raising the threshold of 16S rRNA from the current level of 97.5% to 98.7% could have prevented nearly two-thirds of the more difficult DNA-DNA hybridisations that were carried out”, explains Professor Stackebrandt. “And if the 16S rRNA threshold was increased further, to 99%, then nine out of 10 DNA-DNA hybridisations could have been avoided, without any loss of scientific accuracy in the classifications of the new species.”

There are 400-600 descriptions of new bacteria every year, but it is estimated that up to one billion new species are still waiting to be isolated and named. These bacteria could be holding the keys to speeding up industrial processes, cleaning up the environment, or creating new drugs for human diseases. By reducing the work needed to describe a new species, microbiologists could significantly increase the number of new microbiological products.

Other features in the November 2006 issue of Microbiology Today include:

· ‘Species’ (page 148)
· Virus systematics: taxonomy for the tiny (page 156)
· How many yeasts? (page 160)
· Protozoa: the most abundant predators on earth (page 166)
· Disentangling the trails of evolution (page 170)
· Comment: MicrobiologyBytes (page 192)
These are just some of the articles that appear, together with all the regular features and reports of Society activities.