Vyacheslav (Slava) Klimov (1945-2017): A scientist par excellence, a great human being, a friend, and a Renaissance man.

Vyacheslav Vasilevich (V.V.) Klimov (or Slava, as most of us called him) was born on January 12, 1945 and passed away on May 9, 2017. He began his scientific career at the Bach Institute of Biochemistry of the USSR Academy of Sciences (Akademy Nauk (AN) SSSR), Moscow, Russia, and then, he was associated with the Institute of Photosynthesis, Pushchino, Moscow Region, for about 50 years. He worked in the field of biochemistry and biophysics of photosynthesis. He is known for his studies on the molecular organization of photosystem II (PSII). He was an eminent scientist in the field of photobiology, a well-respected professor, and, above all, an outstanding researcher. Further, he was one of the founding members of the Institute of Photosynthesis in Pushchino, Russia. To most, Slava Klimov was a great human being. He was one of the pioneers of research on the understanding of the mechanism of light energy conversion and of water oxidation in photosynthesis. Slava had many collaborations all over the world, and he is (and will be) very much missed by the scientific community and friends in Russia as well as around the World. We present here a brief biography and some comments on his research in photosynthesis. We remember him as a friendly and enthusiastic person who had an unflagging curiosity and energy to conduct outstanding research in many aspects of photosynthesis, especially that related to PSII.

Consequences of ccmR deletion on respiration, fermentation and H2 metabolism in cyanobacterium Synechococcus sp. PCC 7002.

CcmR, a LysR-type transcriptional regulator, represses the genes encoding components of the high-affinity carbon concentration mechanism in cyanobacteria. Unexpectedly, deletion of the ccmR gene was found to alter the expression of the terminal oxidase and fermentative genes, especially the hydrogenase operon in the cyanobacterium Synechococcus sp. PCC 7002. Consistent with the transcriptomic data, the deletion strain exhibits flux increases (30-50%) in both aerobic O2 respiration and anaerobic H2 evolution. To understand how CcmR influences anaerobic metabolism, the kinetics of autofermentation were investigated following photoautotrophic growth. The autofermentative H2 yield increased by 50% in the CcmR deletion strain compared to the wild-type strain, and increased to 160% (within 20 h) upon continuous removal of H2 from the medium ("milking") to suppress H2 uptake. Consistent with this greater reductant flux to H2 , the mutant excreted less lactate during autofermentation (NAD(P)H consuming pathway). To enhance the rate of NADH production during anaerobic metabolism, the ccmR mutant was engineered to introduce GAPDH overexpression (more NADH production) and LDH deletion (less NADH consumption). The triple mutant (ccmR deletion + GAPDH overexpression + LDH deletion) showed 6-8-fold greater H2 yield than the WT strain, achieving conversion rates of 17 nmol 10(8) cells(-1) h(-1) and yield of 0.87 H2 per glucose equivalent (8.9% theoretical maximum). Simultaneous monitoring of the intracellular NAD(P)H concentration and H2 production rate by these mutants reveals an inverse correspondence between these variables indicating hydrogenase-dependent H2 production as a major sink for consuming NAD(P)H in preference to excretion of reduced carbon as lactate during fermentation. Biotechnol. Bioeng. 2016;113: 1448-1459. © 2015 Wiley Periodicals, Inc.

Perspectives and advances of biological H2 production in microorganisms.

The rapid development of clean fuels for the future is a critically important global challenge for two main reasons. First, new fuels are needed to supplement and ultimately replace depleting oil reserves. Second, fuels capable of zero CO2 emissions are needed to slow the impact of global warming. This review summarizes the development of solar powered bio-H2 production processes based on the conversion of photosynthetic products by fermentative bacteria, as well as using photoheterotrophic and photoautrophic organisms. The use of advanced bioreactor systems and their potential and limitations in terms of process design, efficiency, and cost are also briefly reviewed.