Re: Article: Bacterial Evolution Down in the Depths


"Robert Karl Stonjek" <rstonjek@xxxxxxxxxxxxxx> wrote in message news:dcmakm$2bh4$1@xxxxxxxxxxxxxxxxxxxxxx
> Down in the depths
> Sheilagh Molloy
>
> An obligate photosynthetic anaerobe found in deep-sea hydrothermal vents
> might photosynthesize by harnessing geothermal light rather than solar
> energy, according to recently published results.
>
> Scientists have been exploring the microbiology of deep-sea hydrothermal
> vents - geysers that form along volcanic mid-ocean ridges - using
> submersible vessels for almost 30 years. Until now, life in this environment
> was thought to depend on chemotrophic bacteria, although the identification
> of low-level illumination in the form of 'vent glow' gave a tantalizing hint
> that photosynthesis was a possibility.
>
> Beatty et al. investigated whether geothermal illumination could support
> photosynthesis by analysing samples taken from the effluent plume of a type
> of vent known as a black smoker located at the East Pacific rise. Enrichment
> culturing yielded a non-motile bacterium that has been named GSB1. Analysis
> of the absorption and emission spectra of intact GSB1 cells isolated in pure
> culture - with major peaks at 750 nm and 775 nm, respectively - indicated
> the presence of light-harvesting bacteriochlorophyll c.
>
> Further analysis by electron microscopy revealed the presence of
> light-harvesting chlorosomes, structures that are commonly found in green
> sulphur bacteria. Light energy is transferred to the chlorosome reaction
> centre through the Fenna?Matthews?Olson (FMO) protein; PCR using
> FMO-specific primers amplified a 970-bp FMO segment from GSB1, and sequence
> analysis led the authors to conclude that GSB1 is a green sulphur bacterium
> related to the Chlorobium and Prosthecochloris genera. For growth, GSB1
> requires anaerobic growth conditions, sulphur in the form of elemental
> sulphur or H2S, CO2 and light.
>
> This identification of a green sulphur bacterium in a sample taken from a
> deep-sea hydrothermal vent not only suggests that photosynthesis can take
> place in the absence of sunlight but also once again illustrates the maxim
> that bacteria are the ultimate survivors.
>
> Full Text at Nature
> http://www.nature.com/nrmicro/journal/v3/n8/full/nrmicro1220_fs.html

It seems we still don't have a proof that these bacteria are actually
receiving and utilizing light. All we know is that they have some of the
machinery for doing so.

A speculation: Isn't it possible that the chlorosomes are simply acting
as intermediate carriers in a non-photo-assisted electron transport chain?
ISTM that the environment in which these bacteria are found should be
rich enough in CO, CO2, and H2S to support reductive carbon fixation
even without a photo-assist. Building the chlorosomes when some simpler
electron carrier would do does seem wasteful, but then mother nature only
economizes when she is forced to.


.

Relevant Pages

  • Article: Bacterial Evolution Down in the Depths
    ... An obligate photosynthetic anaerobe found in deep-sea hydrothermal vents ... was thought to depend on chemotrophic bacteria, ... photosynthesis by analysing samples taken from the effluent plume of a type ... analysis led the authors to conclude that GSB1 is a green sulphur bacterium ...
    (sci.bio.evolution)
  • Re: Article: Bacterial Evolution Down in the Depths
    ... >> An obligate photosynthetic anaerobe found in deep-sea hydrothermal vents ... >> was thought to depend on chemotrophic bacteria, ... >> that photosynthesis was a possibility. ... >> light-harvesting chlorosomes, structures that are commonly found in green ...
    (sci.bio.evolution)
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