Proteomic analysis of natural photoheterotrophic mixed consortium for biohydrogen production under nongrowing conditions.

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 redirected 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.