Heliobacterial photosynthesis

Heinnickel, Mark; Golbeck, John H.

doi:10.1007/s11120-007-9162-4

Cited by 71 publications

(70 citation statements)

References 112 publications

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“…A putative anapleurotic carbon fixation pathway for heliobacteria, in which CO 2 assimilation occurs through phosphoenolpyruvate (PEP) carboxylase activity, was proposed by Pickett et al (44) and recently examined again by Heinnickel and Golbeck (18). A similar mechanism was proposed as a means of mixotrophic growth in the aerobic phototrophic proteobacterium Roseobacter denitrificans (51).…”

Section: Genome Properties H Modesticaldum Strain Ice1mentioning

confidence: 96%

“…No mechanism for autotrophic growth has been identified in any heliobacterial species, in contrast to all other anaerobic anoxygenic phototrophs (18). Consistent with these physiological observations, genes encoding essential enzymes of all known autotrophic pathways were not found in the H. modesticaldum genome, including genes encoding ribulose 1,5-bisphosphate carboxylase and phosphoribulokinase (Calvin cycle), citrate lyase (reverse citric acid cycle), carbon monoxide dehydrogenase (reductive acetyl-CoA pathway), and malylCoA lyase (3-hydroxypropionate pathway).…”

Section: Genome Properties H Modesticaldum Strain Ice1mentioning

confidence: 99%

“…Genes predicted to encode all 14 subunits of NADH:quinone oxidoreductase (nuoA to nuoN) were identified in the H. modesticaldum genome. Presumably, electrons from NADH are transferred to menaquinone through this complex and donated to the cytochrome bc complex, which reduces the Rieske [2Fe-2S] subunit (PetC) and cytochrome b L (18) (Fig. 6).…”

Section: Vol 190 2008 Complete Genome Of H Modesticaldum 4693mentioning

confidence: 99%

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The Genome of Heliobacterium modesticaldum , a Phototrophic Representative of the Firmicutes Containing the Simplest Photosynthetic Apparatus

et al. 2008

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Despite the fact that heliobacteria are the only phototrophic representatives of the bacterial phylum Firmicutes, genomic analyses of these organisms have yet to be reported. Here we describe the complete sequence and analysis of the genome of Heliobacterium modesticaldum, a thermophilic species belonging to this unique group of phototrophs. The genome is a single 3.1-Mb circular chromosome containing 3,138 open reading frames. As suspected from physiological studies of heliobacteria that have failed to show photoautotrophic growth, genes encoding enzymes for known autotrophic pathways in other phototrophic organisms, including ribulose bisphosphate carboxylase (Calvin cycle), citrate lyase (reverse citric acid cycle), and malyl coenzyme A lyase (3-hydroxypropionate pathway), are not present in the H. modesticaldum genome. Thus, heliobacteria appear to be the only known anaerobic anoxygenic phototrophs that are not capable of autotrophy. Although for some cellular activities, such as nitrogen fixation, there is a full complement of genes in H. modesticaldum, other processes, including carbon metabolism and endosporulation, are more genetically streamlined than they are in most other low-G؉C gram-positive bacteria. Moreover, several genes encoding photosynthetic functions in phototrophic purple bacteria are not present in the heliobacteria. In contrast to the nutritional flexibility of many anoxygenic phototrophs, the complete genome sequence of H. modesticaldum reveals an organism with a notable degree of metabolic specialization and genomic reduction.

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Section: Genome Properties H Modesticaldum Strain Ice1mentioning

confidence: 96%

Section: Genome Properties H Modesticaldum Strain Ice1mentioning

confidence: 99%

Section: Vol 190 2008 Complete Genome Of H Modesticaldum 4693mentioning

confidence: 99%

See 1 more Smart Citation

The Genome of Heliobacterium modesticaldum , a Phototrophic Representative of the Firmicutes Containing the Simplest Photosynthetic Apparatus

et al. 2008

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“…1B), because CO 2 is produced through the OTCA cycle. Table 2 shows that over 50% aspartate and 60% glutamate were labeled in the ␤-carboxyl group with [1][2][3][4][5][6][7][8][9][10][11][12][13] C]pyruvate as the carbon source, implying that citrate formation is possibly catalyzed by (Re)-citrate synthase ((Re)-CS) (Fig. 3).…”

Section: Carbon Metabolism In H Modesticaldummentioning

confidence: 99%

Carbon Flow of Heliobacteria Is Related More to Clostridia than to the Green Sulfur Bacteria

Tang

Feng

Zhuang

et al. 2010

Journal of Biological Chemistry

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The recently discovered heliobacteria are the only Gram-positive photosynthetic bacteria that have been cultured. One of the unique features of heliobacteria is that they have properties of both the photosynthetic green sulfur bacteria (containing the type I reaction center) and Clostridia (forming heat-resistant endospores). Most of the previous studies of heliobacteria, which are strict anaerobes and have the simplest known photosynthetic apparatus, have focused on energy and electron transfer processes. It has been assumed that like green sulfur bacteria, the major carbon flow in heliobacteria is through the (incomplete) reductive (reverse) tricarboxylic acid cycle, whereas the lack of CO 2 -enhanced growth has not been understood. Here, we report studies to fill the knowledge gap of heliobacterial carbon metabolism. We confirm that the CO 2 -anaplerotic pathway is active during phototrophic growth and that isoleucine is mainly synthesized from the citramalate pathway. Furthermore, to our surprise, our results suggest that the oxidative (forward) TCA cycle is operative and more active than the previously reported reductive (reverse) tricarboxylic acid cycle. Both isotopomer analysis and activity assays suggest that citrate is produced by a putative (Re)-citrate synthase and then enters the oxidative (forward) TCA cycle. Moreover, in contrast to (Si)-citrate synthase, (Re)-citrate synthase produces a different isomer of 2-fluorocitrate that is not expected to inhibit the activity of aconitase.Heliobacteria are a relatively newly discovered group of anaerobic photosynthetic bacteria. All of the cultured heliobacteria require organic carbon for anoxygenic growth, and several of the species can fix nitrogen (1, 2). Heliobacteria are the only cultured Gram-positive photosynthetic bacteria and are phylogenetically related to the bacterial phylum Firmicutes, such as the aerobic Bacillus and anaerobic Clostridia (1). Among 10 cultured heliobacteria (2), Heliobacterium modesticaldum is the only one that can grow at temperatures of Ͼ50°C. Madigan and co-workers (1, 3) reported that pyruvate, lactate, acetate (ϩHCO 3 Ϫ ), or yeast extract can support the phototrophic growth of H. modesticaldum, and our recent studies demonstrated that D-sugars can also support the growth of H. modesticaldum (4).An unusual feature of heliobacteria is that they have properties of both green sulfur bacteria (containing the type I reaction center) and Clostridia (forming heat-resistant endospores) (1). Heliobacteria have the simplest photosynthetic apparatus among the photosynthetic organisms (5), and most of the research on them has been focused on understanding the photosynthetic machinery and energy transfer processes (1, 6 -8).In contrast, our knowledge of phototrophic carbon metabolism by heliobacteria is still poorly developed.Only two reported studies have experimentally probed the carbon metabolism of heliobacteria; one is our recent study with H. modesticaldum (4), and the other is the 1994 report by Kelly and co-workers (9) on Hel...

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“…Heliobacteriaceae with PSItype reaction centres are strict anaerobes that can grow photo-organotrophically in the light and fermentatively in the dark (Gest & Blankenship 2004, Heinnickel & Golbeck 2007, Sattley et al 2008. Their inability to bring about autotrophic inorganic carbon assimilation is attributable to the absence of ATP-citrate lyase; the other reactions of the reductive tricar-boxylic acid cycle (RTCAC) occur in these organisms (Pickett et al 1994, Sattley et al 2008.…”

Section: Organisms With Energy-transforming Photochemistry But Not Camentioning

confidence: 99%

Contributions of anoxygenic and oxygenic phototrophy and chemolithotrophy to carbon and oxygen fluxes in aquatic environments

Raven¹

2009

Aquat. Microb. Ecol.

156

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Estimates of aquatic primary productivity at local, regional or global scales commonly concentrate on oxygenic photolithotrophy. The analysis presented here briefly considers the occurrence and metabolism of other autotrophs sensu lato, i.e. not just the organisms with an autotrophic inorganic carbon assimilation machinery. These other autotrophs include chemolithotrophs and anoxygenic photolithotrophs, of which some use the photosynthetic carbon reduction cycle as do oxygenic photolithotrophs, while others use one of 4 other pathways. The category of other autotrophs also includes organisms that possess photochemical energy transduction machinery but lack autotrophic carbon assimilation; light stimulates the growth rates of these autotrophs and/or increases the fraction of the organic carbon substrate used that is converted into cell material when using light energy. Organisms lacking autotrophic inorganic carbon assimilation influence food webs by increasing the rate, or efficiency, of conversion of dissolved organic carbon ultimately derived from autotrophic inorganic carbon assimilation into particulate organic carbon. Chemolithotrophs and anoxygenic autotrophs today depend on the activities of oxygenic chemolithotrophs for one or more of their growth substrates, and thus contribute to global net primary productivity but not to global gross primary productivity. Global net aquatic primary productivity by oxygenic photolithotrophs is at least 50 Pg C yr . Before the occurrence of oxygenic photolithotrophs in the Archaean, chemolithotrophs and anoxygenic photolithotrophs had a net primary productivity of about 3.4 Pg C yr -1 , which is higher than the present values largely because anoxygenic photolithotrophs were able to inhabit the euphotic zone worldwide.KEY WORDS: Archaean · 3-hydroxypropionate pathway · Inorganic carbon concentrating mechanisms · Photosynthetic carbon reduction cycle · Reductive tricarboxylic acid cycle · Resource use · Ribulose bisphosphate carboxylase-oxygenase Resale or republication not permitted without written consent of the publisherContribution to AME Special 2 'Progress and perspectives in aquatic primary productivity'

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Heliobacterial photosynthesis

Cited by 71 publications

References 112 publications

The Genome of Heliobacterium modesticaldum , a Phototrophic Representative of the Firmicutes Containing the Simplest Photosynthetic Apparatus

The Genome of Heliobacterium modesticaldum , a Phototrophic Representative of the Firmicutes Containing the Simplest Photosynthetic Apparatus

Carbon Flow of Heliobacteria Is Related More to Clostridia than to the Green Sulfur Bacteria

Contributions of anoxygenic and oxygenic phototrophy and chemolithotrophy to carbon and oxygen fluxes in aquatic environments

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