Role of Chloroflexus-like bacteria in cycling of organic compounds in benthic microbial ecosystems
Final Report Abstract
Chloroflexus-like bacteria are filamentous phototrophic bacteria, and these were found to play a major role in the oxygen cycling in a hypersaline microbial mat ecosystem in Northeastern Spain. In this research project a new technique was developed which enabled the discrimination and quantification of aerobic respiration of this group of bacteria in intact communities. This technique, shortly called the 'VIS/NIR light-dark shift technique, utilizes the characteristic that aerobic respiration in Chloroflexus-like bacteria is inhibited by light of the near-infrared (NIR) region. By independently manipulating the visible (VIS) and the NIR light spectrum and simultaneous measurement of oxygen dynamics in the intact microbial mat, the contribution of Chhroflexus-like bacteria could be distinguished from other respiring community members. Striking result was that the present population of Chloroflexus-like bacteria appeared almost fully responsible for the aerobic respiration in the investigated mats, what lead to the conclusion that the role of Chloroflexus-like bacteria and aerobic heterotrophic community members in the microbial mats oxygen cycling was strongly under- and overestimated respectively. These findings are expected to trigger further investigations on the importance of anoxygenic phototrophs in oxygen and carbon cycling in other microbial mats and phototrophic ecosystems. Besides the quantification of their metabolism in intact communities, the diversity of Chhroflexus-like bacteria present was established by molecular techniques. Members of one out of six known Chloroflexus-related genera ('Candidates Chlorothrix') appeared to dominate clone libraries of different mats, what suggests that related species may in fact be the key players of the Chloroflexus community. It is therefore recommended that future studies should specifically focus on the role of 'Candidatus Chlorothrix' relatives and more generally on the importance of anoxygenic phototrophy in the microbial mats oxygen-, carbon- and sulfur-cycling.
Publications
- (2007) Contribution of Chloroflexus respiration to oxygen cycling in a hypersaline microbial mat from Lake Chiprana, Spain. Environmental Microbiology 9(8):2007-2024
Polerecky L, Bachar A, Schoon R, Grinstein M, Jørgensen BB, de Beer D, Jonkers HM
- (2007) Diversity and function of Chloroflexus-like, bacteria in a hypersaline microbial mat: phylogenetic characterization and impact on aerobic respiration. Applied and Environmental Microbiology 73(12):3975-3983
Bachar A, Omoregie E, DeWit R, Jonkers HM
