Genomic insights of an uncultivated Candidate phylum TM6 genome

Genomic insights of an uncultivated Candidate phylum TM6 genome

In an article entitled, ‘Candidate phylum TM6 genome recovered from a hospital sink biofilm provides genomic insights into this uncultivated phylum,’ published in June 25, 2013, issue of PNAS (vol. 110 no. 26; E2390-E2399), the lead author Jeffrey S. McLean with nineteen other associates affiliated to seven different institutes have successfully sequenced the genome of the elusive “Candidate Phylum TM6,” a large group of globally distributed bacteria that have evaded growth in the laboratory. Vast numbers of microbes and entire divisions of bacterial phyla resist cultivation, and, as such, remain poorly understood. One such group known as TM6, first identified in 1996, is a common member of microbial communities that are low in abundance but found in many aqueous environments including domestic drinking water. Using an automated technique that can capture genomes from single cells, Jeffrey S. McLean and colleagues collected TM6 cells from a biofilm in a hospital restroom sink drain and amplified the DNA. The authors then reconstructed a TM6 genome from the DNA fragments (so-called “mini-metagenomes”) with a method that can piece together a genome from sets of overlapping DNA sequences. After a good deal of effort, the team was able to piece together roughly 90 percent of the bacteria’s genome. In so doing they found that the bacteria is not capable of making its own amino acids, which means it likely needs a host to survive. The team theorizes that the bacteria likely live on an amoeba of some sort, or possibly even another kind of bacteria. They still don’t know if TM6 cause problems for humans but suggest that the possibility exists. They might be harmful in ways that have not yet been unraveled, like other bacteria that use an amoeba as a host have been found to be harmful. The findings might guide future cultivation efforts aimed at better understanding the function and ecology of this and similar organisms. Apparently, that development would of course lead to a much better understanding of the bacteria and hopefully to learning whether it’s something we should be worried about or not. [Summarized by Samsad Raqqaque, a Research Associate in]

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