The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Gary M. King - One of the best experts on this subject based on the ideXlab platform.
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Chemolithotrohic Bacteria: Distributions, Functions and Significance in Volcanic Environments
Microbes and Environments, 2007Co-Authors: Gary M. KingAbstract:A mosaic of environments comprises most volcanic ecosystems. Whether terrestrial or submarine, many of these environments contain large deposits of reduced minerals, or experience large fluxes of reduced substrates, especially sulfur-containing compounds. These systems, which also are typically characterized by temperature and pH extremes, have yielded a rich variety of Chemolithotrophic bacteria, and contributed much to our understanding of Chemolithotroph ecology and physiology. However, volcanic ecosystems also consist of environments where inorganic and organic substrates are limiting. In these cases, Chemolithotrophs may still play important roles by scavenging carbon monoxide, hydrogen or both. These gases can support metabolism of facultative Chemolithotrophs, a functional group that includes many nitrogen-fixing bacteria. Facultative Chemolithotrophs may not only represent important early colonists on fresh volcanic substrates (e.g., basalts lacking sulfides), they may also contribute significantly to ecosystem succession through nitrogen fixation and interactions with vascular plants. Analyses of CO and hydrogen consumption by recent deposits on Kilauea volcano show that both substrates support significant activity, while molecular approaches show a high diversity of lithotrophs. Collectively, these and other observations indicate that Chemolithotrophic metabolism is more widespread than generally acknowledged, and likely to play fundamental roles in shaping ecosystem dynamics.
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Disparate distributions of Chemolithotrophs containing form IA or IC large subunit genes for ribulose-1,5-bisphosphate carboxylase/oxygenase in intertidal marine and littoral lake sediments.
FEMS microbiology ecology, 2007Co-Authors: Lisa M. Nigro, Gary M. KingAbstract:The distributions of bacterial form IA and form IC ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) were investigated using Lowes Cove intertidal mudflat and Damariscotta Lake littoral sediments by PCR amplification of 492-495 bp fragments of the large subunit RuBisCO gene, cbbL. Genomic extracts for amplification were obtained from lake surface (upper 2 mm), mudflat surface (upper 2 mm), subsurface (5-7 cm), and soft-shell clam (Mya arenaria) burrow-wall sediments, as well as from a sulfide-oxidizing mat. Phylogenetic analyses of cbbL clone libraries revealed that Lowes Cove sediments were dominated by form IA cbbL-containing sequences most closely related to cbbL genes of sulfur-oxidizing bacteria or sulfide-oxidizing mats. In contrast, Damariscotta Lake cbbL clones contained primarily form IC cbbL sequences, which typify aerobic CO- and hydrogen-oxidizing facultative Chemolithotrophs. Statistical analyses supported clear differentiation of intertidal and lake Chemolithotroph communities, and provided evidence for some differentiation among intertidal communities. amova and libshuff analyses of Lowes Cove libraries suggested that M. arenaria burrow-wall sediments did not harbour distinct communities compared with surface and subsurface sediments, but that surface and subsurface libraries displayed moderate differences. The results collectively support a conceptual model in which the relative distribution of form IA- and IC-containing bacterial Chemolithotrophs depends on sulfide availability, which could reflect the role of sulfate reduction in sediment organic matter metabolism, or the presence of geothermal sulfide sources.
Carlos A. Jerez - One of the best experts on this subject based on the ideXlab platform.
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Phosphate‐starvation induced changes in Thiobacillus ferrooxidans
FEMS microbiology letters, 1993Co-Authors: Michael Seeger, Carlos A. JerezAbstract:We have analysed the response of the acidophilic Chemolithotroph Thiobacillus ferrooxidans to phosphate starvation. Cultivation of the bacteria in the absence of added phosphate induced a remarkable filamentation of the cells. Polyacrylamide gel electrophoresis revealed several proteins whose levels increased upon phosphate limitation, as well as some polypeptides that were exclusively synthesized under this growth limitation. One of the proteins whose level increased by the lack of phosphate was apparently an acid phosphatase with a pH optimum of about 3.8, and a molecular mass of 26 kDa, which was located in the periplasm. The N-terminal sequence of a 26 kDa protein derepressed by starvation, which may correspond to the T. ferrooxidans phosphatase, showed 30% and 35% identity with the known sequence of Lysobacter enzymogenes and Escherichia coli alkaline phosphatases, respectively.
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Research paperPhosphate-starvation induced changes in Thiobacillus ferrooxidans
Fems Microbiology Letters, 1993Co-Authors: Michael Seeger, Carlos A. JerezAbstract:We have analysed the response of the acidophilic Chemolithotroph Thiobacillus ferrooxidans to phosphate starvation. Cultivation of the bacteria in the absence of added phosphate induced a remarkable filamentation of the cells. Polyacrylamide gel electrophoresis revealed several proteins whose levels increased upon phosphate limitation, as well as some polypeptides that were exclusively synthesized under this growth limitation. One of the proteins whose level increased by the lack of phosphate was apparently an acid phosphatase with a pH optimum of about 3.8, and a molecular mass of 26 kDa, which was located in the periplasm. The N-terminal sequence of a 26 kDa protein derepressed by starvation, which may correspond to the T. ferrooxidans phosphatase, showed 30% and 35% identity with the known sequence of Lysobacter enzymogenes and Escherichia coli alkaline phosphatases, respectively.
Michael Seeger - One of the best experts on this subject based on the ideXlab platform.
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Phosphate‐starvation induced changes in Thiobacillus ferrooxidans
FEMS microbiology letters, 1993Co-Authors: Michael Seeger, Carlos A. JerezAbstract:We have analysed the response of the acidophilic Chemolithotroph Thiobacillus ferrooxidans to phosphate starvation. Cultivation of the bacteria in the absence of added phosphate induced a remarkable filamentation of the cells. Polyacrylamide gel electrophoresis revealed several proteins whose levels increased upon phosphate limitation, as well as some polypeptides that were exclusively synthesized under this growth limitation. One of the proteins whose level increased by the lack of phosphate was apparently an acid phosphatase with a pH optimum of about 3.8, and a molecular mass of 26 kDa, which was located in the periplasm. The N-terminal sequence of a 26 kDa protein derepressed by starvation, which may correspond to the T. ferrooxidans phosphatase, showed 30% and 35% identity with the known sequence of Lysobacter enzymogenes and Escherichia coli alkaline phosphatases, respectively.
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Research paperPhosphate-starvation induced changes in Thiobacillus ferrooxidans
Fems Microbiology Letters, 1993Co-Authors: Michael Seeger, Carlos A. JerezAbstract:We have analysed the response of the acidophilic Chemolithotroph Thiobacillus ferrooxidans to phosphate starvation. Cultivation of the bacteria in the absence of added phosphate induced a remarkable filamentation of the cells. Polyacrylamide gel electrophoresis revealed several proteins whose levels increased upon phosphate limitation, as well as some polypeptides that were exclusively synthesized under this growth limitation. One of the proteins whose level increased by the lack of phosphate was apparently an acid phosphatase with a pH optimum of about 3.8, and a molecular mass of 26 kDa, which was located in the periplasm. The N-terminal sequence of a 26 kDa protein derepressed by starvation, which may correspond to the T. ferrooxidans phosphatase, showed 30% and 35% identity with the known sequence of Lysobacter enzymogenes and Escherichia coli alkaline phosphatases, respectively.
Lisa M. Nigro - One of the best experts on this subject based on the ideXlab platform.
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Disparate distributions of Chemolithotrophs containing form IA or IC large subunit genes for ribulose-1,5-bisphosphate carboxylase/oxygenase in intertidal marine and littoral lake sediments.
FEMS microbiology ecology, 2007Co-Authors: Lisa M. Nigro, Gary M. KingAbstract:The distributions of bacterial form IA and form IC ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) were investigated using Lowes Cove intertidal mudflat and Damariscotta Lake littoral sediments by PCR amplification of 492-495 bp fragments of the large subunit RuBisCO gene, cbbL. Genomic extracts for amplification were obtained from lake surface (upper 2 mm), mudflat surface (upper 2 mm), subsurface (5-7 cm), and soft-shell clam (Mya arenaria) burrow-wall sediments, as well as from a sulfide-oxidizing mat. Phylogenetic analyses of cbbL clone libraries revealed that Lowes Cove sediments were dominated by form IA cbbL-containing sequences most closely related to cbbL genes of sulfur-oxidizing bacteria or sulfide-oxidizing mats. In contrast, Damariscotta Lake cbbL clones contained primarily form IC cbbL sequences, which typify aerobic CO- and hydrogen-oxidizing facultative Chemolithotrophs. Statistical analyses supported clear differentiation of intertidal and lake Chemolithotroph communities, and provided evidence for some differentiation among intertidal communities. amova and libshuff analyses of Lowes Cove libraries suggested that M. arenaria burrow-wall sediments did not harbour distinct communities compared with surface and subsurface sediments, but that surface and subsurface libraries displayed moderate differences. The results collectively support a conceptual model in which the relative distribution of form IA- and IC-containing bacterial Chemolithotrophs depends on sulfide availability, which could reflect the role of sulfate reduction in sediment organic matter metabolism, or the presence of geothermal sulfide sources.
Wriddhiman Ghosh - One of the best experts on this subject based on the ideXlab platform.
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Two pathways for thiosulfate oxidation in the alphaproteobacterial Chemolithotroph Paracoccus thiocyanatus SST
Microbiological research, 2019Co-Authors: Moidu Jameela Rameez, Prosenjit Pyne, Subhrangshu Mandal, Sumit Chatterjee, Masrure Alam, Sabyasachi Bhattacharya, Nibendu Mondal, Jagannath Sarkar, Wriddhiman GhoshAbstract:Abstract Chemolithotrophic bacteria oxidize various sulfur species for energy and electrons, thereby operationalizing biogeochemical sulfur cycles in nature. The best-studied pathway of bacterial sulfur-Chemolithotrophy involves direct oxidation of thiosulfate (S2O32−) to sulfate (SO42−) without any free intermediate. This pathway mediated by SoxXAYZBCD is apparently the exclusive mechanism of thiosulfate oxidation in facultatively Chemolithotrophic alphaproteobacteria. Here we explore the molecular mechanisms of sulfur oxidation in the thiosulfate- and tetrathionate(S4O62−)-oxidizing alphaproteobacterium Paracoccus thiocyanatus SST, and compare them with the prototypical Sox process of Paracoccus pantotrophus. Our results reveal a unique case where an alphaproteobacterium has Sox as its secondary pathway of thiosulfate oxidation converting ∼10% of the thiosulfate supplied, whilst ∼90% of the substrate is oxidized via a pathway that produces tetrathionate as an intermediate. Sulfur oxidation kinetics of a deletion mutant showed that thiosulfate-to-tetrathionate conversion, in SST, is catalyzed by a thiosulfate dehydrogenase (TsdA) homolog that has far-higher substrate-affinity than the Sox system of this bacterium, which in turn is also less efficient than the P. pantotrophus Sox. Deletion of soxB abolished sulfate-formation from thiosulfate/tetrathionate, while thiosulfate-to-tetrathionate conversion remained unperturbed. Physiological studies revealed the involvement of glutathione in SST tetrathionate oxidation. However, zero impact of the insertional mutation of a thiol dehydrotransferase (thdT) homolog, together with the absence of sulfite as an intermediate, indicated that SST tetrathionate oxidation is mechanistically novel, and distinct from its betaproteobacterial counterpart mediated by glutathione, ThdT, SoxBCD and sulfite:acceptor oxidoreductase. The present findings highlight extensive functional diversification of sulfur-oxidizing enzymes across phylogenetically close, as well as distant, bacteria.
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Two pathways for thiosulfate oxidation in the alphaproteobacterial Chemolithotroph Paracoccus thiocyanatus SST
2019Co-Authors: Moidu Jameela Rameez, Prosenjit Pyne, Subhrangshu Mandal, Sumit Chatterjee, Masrure Alam, Sabyasachi Bhattacharya, Nibendu Mondal, Jagannath Sarkar, Wriddhiman GhoshAbstract:Abstract Chemolithotrophic bacteria oxidize various sulfur species for energy and electrons, thereby operationalizing biogeochemical sulfur cycles in nature. The best-studied pathway of bacterial sulfur-Chemolithotrophy, involving direct oxidation of thiosulfate to sulfate (without any free intermediate) by the SoxXAYZBCD multienzyme system, is apparently the exclusive mechanism of thiosulfate oxidation in facultatively Chemolithotrophic alphaproteobacteria. Here we explore the molecular mechanisms of sulfur oxidation in the thiosulfate- and tetrathionate-oxidizing alphaproteobacterium Paracoccus thiocyanatus SST, and compare them with the prototypical Sox process characterized in Paracoccus pantotrophus. Our results revealed the unique case where, an alphaproteobacterium has Sox as its secondary pathway of thiosulfate oxidation, converting ∼10% of the thiosulfate supplied whilst 90% of the substrate is oxidized via a Tetrathionate-Intermediate pathway. Knock-out mutation, followed by the study of sulfur oxidation kinetics, showed that thiosulfate-to-tetrathionate conversion, in SST, is catalyzed by a thiosulfate dehydrogenase (TsdA) homolog that has far-higher substrate-affinity than the Sox system of this bacterium, which, remarkably, is also less efficient than the P. pantotrophus Sox. soxB-deletion in SST abolished sulfate-formation from thiosulfate/tetrathionate while thiosulfate-to-tetrathionate conversion remained unperturbed. Physiological studies revealed the involvement of glutathione in SST tetrathionate oxidation. However, zero impact of the knock-out of a thiol dehydrotransferase (thdT) homolog, together with no production of sulfite as an intermediate, indicated that tetrathionate oxidation in SST is mechanistically novel, and distinct from its betaproteobacterial counterpart mediated by glutathione, ThdT, SoxBCD and sulfite:acceptor oxidoreductase. All the present findings collectively highlight extensive functional diversification of sulfur-oxidizing enzymes across phylogenetically close, as well as distant, bacteria.