Project description:We cultivated two halo-alkaliphilic cyanobacteria consortia in chemostats at pH 10.2-11.4. One consortium was dominated by Ca. Sodalinema alkaliphilum, the other by a species of Nodosilinea. These two cyanobacteria dominate natural communities in Canadian and Asian alkaline soda lakes. We show that increasing the pH decreased biomass yield. This decrease was caused, in part, by a dramatic increase in carbon transfer to heterotrophs. At pH 11.4, cyanobacterial growth became limited by bicarbonate uptake, which was mainly ATP-dependent. In parallel, the higher the pH, the more sensitive cyanobacteria became to light, resulting in photoinhibition and upregulation of DNA repair systems.
Project description:A biohydrogen and polyhydroxyalkanoates(PHA)-producing natural photoheterotrophic mixed culture composed mainly by Rhodopseudomonas palustris and Clostridium sp was studied by a proteomic analysis under non-growth conditions (nitrogen-absence and organic acids). Proteins in C. pasteurianum were upregulated, particularly those related to stress response. In contrast, C. pasteurianum in the consortium did not present such proteins, showing the advantage of being part of it. Both cultures showed proteins involved in organic acid metabolism and biohydrogen production, such as lactate dehydrogenase, ferredoxins, and hydrogenases. Proteomes of R. palustris as single culture and in consortium showed that organic acids were redirect into central carbon pathways to generate reduced equivalents for biohydrogen production. Light-harvesting proteins and fatty acid metabolism linked to PHA accumulation were also upregulated. This study provides insights into how the proteomes of individual organisms and their consortium counterparts adapt to non-growth conditions, shedding light on how microbial interactions influence protein expression.