Normally I avoid writing about discoveries in non Open Access journals. But I cannot help myself here. On Friday a wickedly cool paper was published in a journal that I will not name here. In this paper they describe a new bacterium: “Candidatus Chloracidobacterium thermophilum.” It is REALLY rare for a new bacteria to be described in a journal like this one. How did they get it in this journal? Well this organism represents the first new photosynthetic lineage of organisms discovered in many many many years. The bacterium is in the phylum Acidobacteria and can carry out aerobic photosynthesis. Prior to this discovery, photosynthesis was only known in five evolutionary lineages – all of them bacteria: Cyanobacteria, Chlorobi, Chloroflexi, Proteobacteria and Firmicutes. Photosynthesis in plants, algae and other eukaryotes all came from symbioses with cyanobacteria to these five groups represented the only “primary” photosynthetic lineages. Thus it is a big deal to find a sixth lineage having photosynthesis.
And – here is the fun part. How did they find this? With the help of metagenomics.
Only five bacterial phyla with members capable of chlorophyll (Chl)–based phototrophy are presently known. Metagenomic data from the phototrophic microbial mats of alkaline siliceous hot springs in Yellowstone National Park revealed the existence of a distinctive bacteriochlorophyll (BChl)–synthesizing, phototrophic bacterium. A highly enriched culture of this bacterium grew photoheterotrophically, synthesized BChls a and c under oxic conditions, and had chlorosomes and type 1 reaction centers. “Candidatus Chloracidobacterium thermophilum” is a BChl-producing member of the poorly characterized phylum Acidobacteria.
That is, they saw the first hints of this through analysis of metagenomic data which was generated by isolating DNA from a Yellowstone hot spring and sequencing the snot out of it. Anyway – as some might have guessed – my only lament about this paper is that it is in a non Open Access journal (I tried to convince the lead author to submit elsewhere but was not convincing enough I guess). It really is too bad – it would be nice to post some of their figures here for others to look at and it this paper would make a great one to use for educating the public about metagenomics. But alas the public cannot get this from Science for at least 1 year and bloggers and other news sources cannot really run with the story because of the copyright limitations. So – great science and great example of the power of metagenomics but restricted public use.
Jonathan Eisen's Lab 