In contrast, DCMU reduced the respiration rate in A. In addition, only CCCP enhanced the respiration rate, further reducing the O 2 level. Under illumination, CCCP and DCMU inhibited chlorophyll fluorescence, resulting in a low level of O 2, which promoted bidirectional hydrogenase activity in A. The highest dark fermentative H 2 production rate of μmol H 2 g −1 dry weight h −1 was found in cells treated with 0.5 μM CCCP after 2 h of dark incubation. halophytica during dark incubation, because CCCP functions as an uncoupling agent of oxidative phosphorylation. Only CCCP treatment increased H 2 production of A. halophytica incubated in the dark showed a significant increase in H 2 production compared with cells that were incubated in the light. The highest H 2 photoproduction rates, and μmol H 2 g −1 dry weight h −1, were found in cells treated with 0.5 μM CCCP and 50 μM DCMU, respectively. halophytica treated with CCCP and DCMU produced H 2 at three to five times the rate of untreated cells, when exposed to light. halophytica under light and dark conditions and on photosynthetic and respiratory activities. The present study aimed to investigate the effects of the photosystem II inhibitors carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) on H 2 production of A. One factor limiting the H 2 photoproduction of this cyanobacterium is an inhibition of bidirectional hydrogenase activity by oxygen (O 2) obtained from splitting water molecules via photosystem II activity. The unicellular halotolerant cyanobacterium Aphanothece halophytica is a potential dark fermentative producer of molecular hydrogen (H 2) that produces very little H 2 under illumination.

What is cccp treated cells