Pansook Sunisa, Incharoensakdi Aran, Phunpruch Saranya
Department of Biology, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand.
Laboratory of Cyanobacterial Biotechnology, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
ScientificWorldJournal. 2019 Jun 27;2019:1030236. doi: 10.1155/2019/1030236. eCollection 2019.
The unicellular halotolerant cyanobacterium is a potential dark fermentative producer of molecular hydrogen (H) that produces very little H under illumination. One factor limiting the H photoproduction of this cyanobacterium is an inhibition of bidirectional hydrogenase activity by oxygen (O) obtained from splitting water molecules via photosystem II activity. 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 production of . under light and dark conditions and on photosynthetic and respiratory activities. The results showed that . treated with CCCP and DCMU produced H at three to five times the rate of untreated cells, when exposed to light. The highest H photoproduction rates, 2.26 ± 0.24 and 3.63 ± 0.26 mol Hg dry weight h, were found in cells treated with 0.5 M CCCP and 50 M DCMU, respectively. Without inhibitor treatment, . incubated in the dark showed a significant increase in H production compared with cells that were incubated in the light. Only CCCP treatment increased H production of . during dark incubation, because CCCP functions as an uncoupling agent of oxidative phosphorylation. The highest dark fermentative H production rate of 39.50 ± 2.13 mol Hg dry weight h was found in cells treated with 0.5 M CCCP after 2 h of dark incubation. Under illumination, CCCP and DCMU inhibited chlorophyll fluorescence, resulting in a low level of O, which promoted bidirectional hydrogenase activity in . cells. In addition, only CCCP enhanced the respiration rate, further reducing the O level. In contrast, DCMU reduced the respiration rate in .
单细胞耐盐蓝细菌是分子氢（H₂）的潜在暗发酵生产者，在光照下产生的H₂很少。限制这种蓝细菌光产H₂的一个因素是通过光系统II活性分解水分子获得的氧气（O₂）对双向氢化酶活性的抑制。本研究旨在研究光系统II抑制剂羰基氰化物间氯苯腙（CCCP）和3-(3,4-二氯苯基)-1,1-二甲基脲（DCMU）对该蓝细菌在光照和黑暗条件下H₂产生以及光合和呼吸活性的影响。结果表明，用CCCP和DCMU处理的该蓝细菌在光照下产生H₂的速率是未处理细胞的三到五倍。在用0.5 M CCCP和50 μM DCMU处理的细胞中，分别发现最高的光产H₂速率，即2.26±0.24和3.63±0.26 μmol H₂ g干重⁻¹ h⁻¹。在没有抑制剂处理的情况下，与在光照下培养的细胞相比，在黑暗中培养的该蓝细菌H₂产量显著增加。只有CCCP处理增加了黑暗培养期间该蓝细菌的H₂产量，因为CCCP作为氧化磷酸化的解偶联剂发挥作用。在黑暗培养2小时后，在用0.5 M CCCP处理的细胞中发现最高的暗发酵H₂产生速率为39.50±2.13 μmol H₂ g干重⁻¹ h⁻¹。在光照下，CCCP和DCMU抑制叶绿素荧光，导致低水平的O₂，这促进了该蓝细菌细胞中的双向氢化酶活性。此外，只有CCCP提高了呼吸速率，进一步降低了O₂水平。相比之下，DCMU降低了该蓝细菌的呼吸速率。
