scholarly journals Redirection of Metabolism for Biological Hydrogen Production

2007 ◽  
Vol 73 (5) ◽  
pp. 1665-1671 ◽  
Author(s):  
Federico E. Rey ◽  
Erin K. Heiniger ◽  
Caroline S. Harwood
Keyword(s):  
Nitrogen Fixation ◽  
Hydrogen Production ◽  
Photosynthetic Bacteria ◽  
Rhodopseudomonas Palustris ◽  
Photosynthetic Bacterium ◽  
Selection Strategy ◽  
Wild Type ◽  
Purple Photosynthetic Bacteria ◽  
Mutant Strains ◽  
Different Strains

ABSTRACT A major route for hydrogen production by purple photosynthetic bacteria is biological nitrogen fixation. Nitrogenases reduce atmospheric nitrogen to ammonia with the concomitant obligate production of molecular hydrogen. However, hydrogen production in the context of nitrogen fixation is a rather inefficient process because about 75% of the reductant consumed by the nitrogenase is used to generate ammonia. In this study we describe a selection strategy to isolate strains of purple photosynthetic bacteria in which hydrogen production is necessary for growth and independent of nitrogen fixation. We obtained four mutant strains of the photosynthetic bacterium Rhodopseudomonas palustris that produce hydrogen constitutively, even in the presence of ammonium, a condition where wild-type cells do not accumulate detectable amounts of hydrogen. Some of these strains produced up to five times more hydrogen than did wild-type cells growing under nitrogen-fixing conditions. Transcriptome analyses of the hydrogen-producing mutant strains revealed that in addition to the nitrogenase genes, 18 other genes are potentially required to produce hydrogen. The mutations that caused constitutive hydrogen production mapped to four different sites in the NifA transcriptional regulator in the four different strains. The strategy presented here can be applied to the large number of diverse species of anoxygenic photosynthetic bacteria that are known to exist in nature to identify strains for which there are fitness incentives to produce hydrogen.

scholarly journals Expression of Uptake Hydrogenase and Molybdenum Nitrogenase in Rhodobacter capsulatus Is Coregulated by the RegB-RegA Two-Component Regulatory System

2000 ◽  
Vol 182 (10) ◽  
pp. 2831-2837 ◽  
Author(s):  
Sylvie Elsen ◽  
Wanda Dischert ◽  
Annette Colbeau ◽  
Carl E. Bauer
Keyword(s):  
Photosynthetic Bacteria ◽  
Rhodobacter Capsulatus ◽  
Regulatory System ◽  
Photosynthetic Bacterium ◽  
Uptake Hydrogenase ◽  
Carbon And Nitrogen ◽  
Cellular Energy ◽  
Purple Photosynthetic Bacteria ◽  
Two Component

ABSTRACT Purple photosynthetic bacteria are capable of generating cellular energy from several sources, including photosynthesis, respiration, and H2 oxidation. Under nutrient-limiting conditions, cellular energy can be used to assimilate carbon and nitrogen. This study provides the first evidence of a molecular link for the coregulation of nitrogenase and hydrogenase biosynthesis in an anoxygenic photosynthetic bacterium. We demonstrated that molybdenum nitrogenase biosynthesis is under the control of the RegB-RegA two-component regulatory system in Rhodobacter capsulatus. Footprint analyses and in vivo transcription studies showed that RegA indirectly activates nitrogenase synthesis by binding to and activating the expression of nifA2, which encodes one of the two functional copies of the nif-specific transcriptional activator, NifA. Expression of nifA2 but notnifA1 is reduced in the reg mutants up to eightfold under derepressing conditions and is also reduced under repressing conditions. Thus, although NtrC is absolutely required fornifA2 expression, RegA acts as a coactivator ofnifA2. We also demonstrated that in regmutants, [NiFe]hydrogenase synthesis and activity are increased up to sixfold. RegA binds to the promoter of the hydrogenase gene operon and therefore directly represses its expression. Thus, the RegB-RegA system controls such diverse processes as energy-generating photosynthesis and H2 oxidation, as well as the energy-demanding processes of N2 fixation and CO2 assimilation.

Immobilization and Ammonia Removal of Photosynthetic Bacteria

2012 ◽  
Vol 610-613 ◽  
pp. 311-314 ◽  
Author(s):  
Pei Rong Zhan ◽  
Wei Liu
Keyword(s):  
Electron Microscopy ◽  
Amino Acids ◽  
Photosynthetic Bacteria ◽  
Rhodopseudomonas Palustris ◽  
Carbon Sources ◽  
Water Environment ◽  
Photosynthetic Bacterium ◽  
Ammonia Removal ◽  
Fish Pond ◽  
Immobilized Microorganisms

The photosynthetic bacteria have been widely used in improving the water environment, especially for pollutant purification. A photosynthetic bacterium was isolated from fish pond sludge using various methods. The bacterium is rod-shaped and slightly curved, and they reproduce by budding. It grew anaerobically when exposed to light and aerobically in darkness. Based on electron microscopy, utilization of carbon sources and amino acids, and factors required for growth, the bacterium is identified as Rhodopseudomonas palustris. The R. palustris was immobilized using different carriers to increase its concentration and its targeted use. The results show that immobilization of the bacteria stabilized the ammonia removal and protected the bacteria from predation by plankton. The method is also easy to use and prolonged the purification effect in the reactor. The immobilized microorganisms are 30%–40% more effective than free bacteria in removing ammonia.

scholarly journals Investigating and modelling the effect of light intensity on Rhodopseudomonas palustris growth

2021 ◽  
Author(s):  
Brandon Ross ◽  
Robert William McClelland Pott
Keyword(s):  
Experimental Data ◽  
Light Intensity ◽  
Photosynthetic Bacteria ◽  
Rhodopseudomonas Palustris ◽  
Photosynthetic Bacterium ◽  
Light Penetration ◽  
Tubular Photobioreactor ◽  
Photobioreactor Design ◽  
High Purity Hydrogen ◽  
Effect Of Light

Photosynthetic bacteria can be useful biotechnological tools – they produce a variety of valuable products, including high purity hydrogen, and can simultaneously treat recalcitrant wastewaters. However, while photobioreactors have been designed and modelled for photosynthetic algae and cyanobacteria, there has been less work on understanding the effect of light in photosynthetic bacterial fermentations. In order to design photobioreactors, and processes using these organisms, robust models of light penetration, utilisation and conversion are needed. This article uses experimental data from a tubular photobioreactor designed to focus in on light intensity effects, to model the effect of light intensity on the growth of Rhodopseudomonas palustris, a model photosynthetic bacterium. The work demonstrates that growth is controlled by light intensity, and that this organism does experience photoinhibition above 600 W/m2, which has implications for outdoor applications. Further, the work presents a model for light penetration in circular photobioreactors, which tends to be the most common geometry. The work extends the modelling tools for these organisms, and will allow for better photobioreactor design, and the integration of modelling tools in designing processes which use photosynthetic bacteria.

Hydrogen production system using purple photosynthetic bacteria

2004 ◽  
Vol 2004.10 (0) ◽  
pp. 135-136
Author(s):  
Makoto YOSHIDA ◽  
Shoichiro KAWAYOKE ◽  
Junpei KAMICHI ◽  
Masahiro OTA
Keyword(s):  
Hydrogen Production ◽  
Production System ◽  
Photosynthetic Bacteria ◽  
Purple Photosynthetic Bacteria
Sign in / Sign up

Export Citation Format

Share Document