The adherence-associated Fdp fasciclin I domain protein of the biohydrogen producer is regulated by the global Prr pathway.

Expression of encoding a fasciclin I domain protein important for adherence in the hydrogen-producing bacterium was investigated under a range of conditions to gain insights into optimization of adherence for immobilization strategies suitable for H production. The promoter was linked to a reporter and expressed in wild type and in PRRB and PRRA mutant strains of the Prr regulatory pathway. Expression was significantly negatively regulated by Prr under all conditions of aerobiosis tested including anaerobic conditions (required for H production), and aerobically regardless of growth phase, growth medium complexity or composition, carbon source, heat and cold shock and dark/light conditions. Negative regulation by Prr was reflected in cellular levels of translated Fdp protein. Since Prr is required directly for nitrogenase expression, we propose optimization of Fdp-based adherence in for immobilized biohydrogen production by inactivation of the PrrA binding site(s) upstream of .