Interspecies interaction and diversity of green sulfur bacteria [thesis]

Johannes Müller
2012
The following work is shedding light on the phylogenetic classification on the family of the Chlorobiacea, the members of which are showing signs of preadaptation to symbiosis. Symbioses consisting of purely prokaryotic associations between phylogenetically distinct bacterial species have been widely documented. Only few are available as a laboratory culture to elucidate the molecular basis of their interaction. One of these few model organisms is the phototrophic consortium "Chlorochromatium
more » ... "Chlorochromatium aggregatum". It consists of 12-20 green sulfur bacteria epibionts surrounding a central, Betaproteobacterium in a highly ordered fashion. The phototrophic partner bacterium, belonging to the green sulfur bacteria, is available in pure culture and its physiology has been studied in detail. In this work, novel insights into the physiology of the central bacterium that was previously uncharacterized are provided. The family of the Chlorobiaceae represents a phylogenetically coherent and isolated group within the domain Bacteria. Green sulfur bacteria are obligate photolithoautotrophs that require highly reducing conditions for growth and can utilize only a very limited number of carbon substrates. These bacteria thus inhabit a very narrow ecologic niche. For the phylogenetic studies on green sulfur bacteria, 323 16S rRNA gene sequences, including cultured species as well as environmental sequences were analysed. By rarefaction analysis and statistical projection, it was shown that the data represent nearly the whole spectrum of green sulfur bacterial species that can be found in the sampled habitats. Sequences of cultured species, however, did not even cover half of the biodiversity. In the 16S rDNA gene tree, different clusters were found that in most cases correlated with physiological adaptations of the included species. By combining all sampling sites of green sulfur bacteria in a world map, large, unsampled areas were revealed and it could be shown that in some regions, a non-random distribution of GSB occurred. The wide d [...]
doi:10.5282/edoc.15614 fatcat:cxxocpudbnfsvls6komsnl2d3e