The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Helge Niemann - One of the best experts on this subject based on the ideXlab platform.
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occurrence of unusual steroids and hopanoids derived from aerobic methanotrophs at an active Marine Mud volcano
Organic Geochemistry, 2008Co-Authors: Marcus Elvert, Helge NiemannAbstract:Surface sediment samples from two microbial habitats (centre and adjacent Beggiatoa mats) at an active CH4-emitting Mud volcano on the Norwegian margin of the Barents Sea (Haakon Mosby Mud Volcano – HMMV) were analyzed for their steroid and hopanoid biomarker distributions and associated stable carbon isotopic composition. Substantial abundances of a suite of six steroids (four 4α-methyl sterols and two 4α-methyl steroid diols) and three hopanoids (diploptene, diplopterol and Δ2-diplopterol) were found, together with biomarkers from anaerobic methanotrophic consortia (ANME-3/Desulfobulbus aggregates) at the surface sediment of the mats. All of the steroid and hopanoid biomarkers, some not been described before, were substantially depleted in 13C (δ13C between −77‰ and −68‰), proving biosynthesis by an organism involved in methane consumption. Molecular analysis (16S rRNA sequencing and fluorescence in situ hybridisation) performed in a parallel study showed that, besides ANME-3/Desulfobulbus consortia, aerobic methanotrophs of the order Methylococcales are also abundant with high cell numbers. These independent findings suggest a spatially close vicinity of active aerobic and anaerobic methanotrophic communities on the order of millimetres, not reported before for the Marine environment. At the centre location, where methane oxidation is performed solely by Methylococcales species, predominantly 4α-methyl-3β-sterols, together with high abundances of specific fatty acids (i.e. C16:1ω9c and C16:1ω8c), were detected. The additional presence of new and unusual biomarkers for aerobic methanotrophy at the Beggiatoa mats seems to indicate either varying strains of Methylococcales types or an energy stress adaptation of the dominant species at the latter sampling site. Moreover, consideration is given to the new biomarkers being intermediates in the biosynthetic formation of steroids and hopanoids in methanotrophic bacteria.
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Novel microbial communities of the Haakon Mosby Mud volcano and their role as a methane sink.
Nature, 2006Co-Authors: Helge Niemann, Marcus Elvert, Tina Lösekann, Dirk De Beer, Thierry Nadalig, Katrin Knittel, Rudolf Amann, Eberhard J Sauter, Michael Schlüter, Michael KlagesAbstract:Mud volcanism is an important natural source of the greenhouse gas methane to the hydrosphere and atmosphere. Recent investigations show that the number of active subMarine Mud volcanoes might be much higher than anticipated (for example, see refs 3-5), and that gas emitted from deep-sea seeps might reach the upper mixed ocean. Unfortunately, global methane emission from active subMarine Mud volcanoes cannot be quantified because their number and gas release are unknown. It is also unclear how efficiently methane-oxidizing microorganisms remove methane. Here we investigate the methane-emitting Haakon Mosby Mud Volcano (HMMV, Barents Sea, 72 degrees N, 14 degrees 44' E; 1,250 m water depth) to provide quantitative estimates of the in situ composition, distribution and activity of methanotrophs in relation to gas emission. The HMMV hosts three key communities: aerobic methanotrophic bacteria (Methylococcales), anaerobic methanotrophic archaea (ANME-2) thriving below siboglinid tubeworms, and a previously undescribed clade of archaea (ANME-3) associated with bacterial mats. We found that the upward flow of sulphate- and oxygen-free Mud volcano fluids restricts the availability of these electron acceptors for methane oxidation, and hence the habitat range of methanotrophs. This mechanism limits the capacity of the microbial methane filter at active Marine Mud volcanoes to
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novel microbial communities of the haakon mosby Mud volcano and their role as a methane sink
Nature, 2006Co-Authors: Marcus Elvert, Helge Niemann, Tina Lösekann, Dirk De Beer, Thierry Nadalig, Katrin Knittel, Rudolf AmannAbstract:SubMarine Mud volcanoes may be major players in the emission of the greenhouse gas methane. A select group of microorganisms, called methanotrophs, can consume this gas, but their impact on methane emission in this environment is not well understood. A study of the waters around a Mud volcano in the Barents Sea has identified three key methanotrophic communities: aerobic bacteria, anaerobic archaea living beneath tubeworms, and previously undescribed archaea associated with bacterial mats. A natural cap on the capacity of the microbial methane filter was also discovered: the upward flow of sulphate- and oxygen-free volcanic fluids restricts the efficiency of methane oxidation, allowing much of the methane to escape to the hydrosphere and potentially the atmosphere. Mud volcanism is an important natural source of the greenhouse gas methane to the hydrosphere and atmosphere1,2. Recent investigations show that the number of active subMarine Mud volcanoes might be much higher than anticipated (for example, see refs 3–5), and that gas emitted from deep-sea seeps might reach the upper mixed ocean6,7,8. Unfortunately, global methane emission from active subMarine Mud volcanoes cannot be quantified because their number and gas release are unknown9. It is also unclear how efficiently methane-oxidizing microorganisms remove methane. Here we investigate the methane-emitting Haakon Mosby Mud Volcano (HMMV, Barents Sea, 72° N, 14° 44′ E; 1,250 m water depth) to provide quantitative estimates of the in situ composition, distribution and activity of methanotrophs in relation to gas emission. The HMMV hosts three key communities: aerobic methanotrophic bacteria (Methylococcales), anaerobic methanotrophic archaea (ANME-2) thriving below siboglinid tubeworms, and a previously undescribed clade of archaea (ANME-3) associated with bacterial mats. We found that the upward flow of sulphate- and oxygen-free Mud volcano fluids restricts the availability of these electron acceptors for methane oxidation, and hence the habitat range of methanotrophs. This mechanism limits the capacity of the microbial methane filter at active Marine Mud volcanoes to <40% of the total flux.
Elisabeth M Brown - One of the best experts on this subject based on the ideXlab platform.
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Geoacoustic Inversion for a New England Mud Patch Sediment Using the Silt-Suspension Theory of Marine Mud
IEEE Journal of Oceanic Engineering, 2020Co-Authors: Elisabeth M Brown, Jason D. Chaytor, William L SiegmannAbstract:This article provides an application of the silt-suspension theory to a Bayesian-inference inversion for the geo-acoustic parameters in Marine Mud. The theory, with consequences that have been developed recently, postulates a suspension of water and clay mineral card-houses that supports moderately dilute concentrations of silt particles. The approach is an example of a physically based model inversion, in which parameters representing physical Mud-layer properties are obtained by inversion and used to produce estimates of geoacoustic properties, including their frequency dependence. The acoustic data are from a combustive source signal propagated along a track, located over several meters of fine-grained Mud in the New England Mud Patch, to a single hydrophone on a receiver array during the 2017 Seabed Characterization Experiment. Data extracted from a nearby piston core inform the physical modeling, with selections of inversion parameters guided by both sensitivity analyses and bounds from archival and core measurements. Results show the feasibility of this inversion approach. The estimates of Mud density and sound speed are close to values obtained independently. The frequency dependence of attenuation is estimated over the full low-frequency source band and has an approximate power exponent of 1.72.
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influence of sand silt particle size distributions on compressional wave attenuation in Marine Mud sediments
Journal of the Acoustical Society of America, 2017Co-Authors: Elisabeth M Brown, Allan D Pierce, William L SiegmannAbstract:High porosity Marine Mud from different sites typically contains different amounts of clay, sand, and silt particles, along with other material. A recent talk [Pierce et al., ASA Honolulu, 5aAO1 (2016)] explored a mechanism for why sand and silt particles in suspension can provide the dominant contributions to the frequency dependence of compressional wave attenuation. The card-house structure of the clay is critical in supporting the particles and keeping them separated. Example calculations for spherical particles of the same size showed physically reasonable attenuation behavior at low and high frequencies. This presentation considers extensions of the approach, particularly accounting for distributions of particle sizes, and emphasizes comparisons of attenuation predictions with available field data. Using reasonable assumptions about the clay volume and the sand and silt distributions, it is possible to estimate the numbers of sand and silt particles, and consequently the attenuation, from the sedime...
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Influence of sand/silt particle size distributions on compressional wave attenuation in Marine Mud sediments
Journal of the Acoustical Society of America, 2017Co-Authors: Elisabeth M Brown, Allan D Pierce, William L SiegmannAbstract:High porosity Marine Mud from different sites typically contains different amounts of clay, sand, and silt particles, along with other material. A recent talk [Pierce et al., ASA Honolulu, 5aAO1 (2016)] explored a mechanism for why sand and silt particles in suspension can provide the dominant contributions to the frequency dependence of compressional wave attenuation. The card-house structure of the clay is critical in supporting the particles and keeping them separated. Example calculations for spherical particles of the same size showed physically reasonable attenuation behavior at low and high frequencies. This presentation considers extensions of the approach, particularly accounting for distributions of particle sizes, and emphasizes comparisons of attenuation predictions with available field data. Using reasonable assumptions about the clay volume and the sand and silt distributions, it is possible to estimate the numbers of sand and silt particles, and consequently the attenuation, from the sedime...
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effect of sand and silt particles on the attenuation of compressional waves in Marine Mud sediments
Journal of the Acoustical Society of America, 2016Co-Authors: Allan D Pierce, William L Siegmann, Elisabeth M BrownAbstract:Mud in Marine sediments is a mixture of clay, sand, and silt particles. Present paper follows up on a suggestion by Holland and Dosso (JASA, 2013) that the variability of the measured frequency-dependent compressional wave attenuation may be caused by the variability of the amounts of sand and silt particles. The premise is that the porosity for the Mud is high and that the sand and silt particles are in suspension. They do not settle out to the bottom of the layer because the card-house fabric of the clay particles tends to hold them in place. This supposition leads to a theory where the clay configuration gives a base-line attenuation, and the contribution from the individual sand and silt particles is additive. The estimation of the latter is distinguished from the existing theories of attenuation of sound in sandy/silty sediments in that the particles are presumed not to touch each other. Particles are assumed to be spherical and there is no slip between particle surfaces and the surrounding water. Ea...
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suspension theory for the effect of silt particles on attenuation of compressional waves in Marine Mud sediments
171st Meeting of the Acoustical Society of America, 2016Co-Authors: Allan D Pierce, William L Siegmann, Elisabeth M BrownAbstract:Mud in Marine sediments is a mixture of clay and silt particles. Paper follows a suggestion by Holland and Dosso (JASA, 2013) that the variability of the measured frequency-dependent compressional wave attenuation may be caused by the variability of the amounts of silt particles. The premise is that the silt particles are in suspension. They do not settle out to the bottom of the layer because the card-house fabric of the clay particles tends to hold them in place. This theory leads to a supposition where the clay configuration gives a negligible base-line attenuation, and the contribution from the individual silt particles is additive. The estimation of the latter is distinguished from the existing theories of attenuation of sound in sandy/silty sediments in that the particles are presumed not to touch each other. Particles are assumed to be spherical and there is no slip between particles and the surrounding water. Earlier formulations of attenuation in suspensions by Lamb (Hydrodynamics) and Urick (JAS...
Marcus Elvert - One of the best experts on this subject based on the ideXlab platform.
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occurrence of unusual steroids and hopanoids derived from aerobic methanotrophs at an active Marine Mud volcano
Organic Geochemistry, 2008Co-Authors: Marcus Elvert, Helge NiemannAbstract:Surface sediment samples from two microbial habitats (centre and adjacent Beggiatoa mats) at an active CH4-emitting Mud volcano on the Norwegian margin of the Barents Sea (Haakon Mosby Mud Volcano – HMMV) were analyzed for their steroid and hopanoid biomarker distributions and associated stable carbon isotopic composition. Substantial abundances of a suite of six steroids (four 4α-methyl sterols and two 4α-methyl steroid diols) and three hopanoids (diploptene, diplopterol and Δ2-diplopterol) were found, together with biomarkers from anaerobic methanotrophic consortia (ANME-3/Desulfobulbus aggregates) at the surface sediment of the mats. All of the steroid and hopanoid biomarkers, some not been described before, were substantially depleted in 13C (δ13C between −77‰ and −68‰), proving biosynthesis by an organism involved in methane consumption. Molecular analysis (16S rRNA sequencing and fluorescence in situ hybridisation) performed in a parallel study showed that, besides ANME-3/Desulfobulbus consortia, aerobic methanotrophs of the order Methylococcales are also abundant with high cell numbers. These independent findings suggest a spatially close vicinity of active aerobic and anaerobic methanotrophic communities on the order of millimetres, not reported before for the Marine environment. At the centre location, where methane oxidation is performed solely by Methylococcales species, predominantly 4α-methyl-3β-sterols, together with high abundances of specific fatty acids (i.e. C16:1ω9c and C16:1ω8c), were detected. The additional presence of new and unusual biomarkers for aerobic methanotrophy at the Beggiatoa mats seems to indicate either varying strains of Methylococcales types or an energy stress adaptation of the dominant species at the latter sampling site. Moreover, consideration is given to the new biomarkers being intermediates in the biosynthetic formation of steroids and hopanoids in methanotrophic bacteria.
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Novel microbial communities of the Haakon Mosby Mud volcano and their role as a methane sink.
Nature, 2006Co-Authors: Helge Niemann, Marcus Elvert, Tina Lösekann, Dirk De Beer, Thierry Nadalig, Katrin Knittel, Rudolf Amann, Eberhard J Sauter, Michael Schlüter, Michael KlagesAbstract:Mud volcanism is an important natural source of the greenhouse gas methane to the hydrosphere and atmosphere. Recent investigations show that the number of active subMarine Mud volcanoes might be much higher than anticipated (for example, see refs 3-5), and that gas emitted from deep-sea seeps might reach the upper mixed ocean. Unfortunately, global methane emission from active subMarine Mud volcanoes cannot be quantified because their number and gas release are unknown. It is also unclear how efficiently methane-oxidizing microorganisms remove methane. Here we investigate the methane-emitting Haakon Mosby Mud Volcano (HMMV, Barents Sea, 72 degrees N, 14 degrees 44' E; 1,250 m water depth) to provide quantitative estimates of the in situ composition, distribution and activity of methanotrophs in relation to gas emission. The HMMV hosts three key communities: aerobic methanotrophic bacteria (Methylococcales), anaerobic methanotrophic archaea (ANME-2) thriving below siboglinid tubeworms, and a previously undescribed clade of archaea (ANME-3) associated with bacterial mats. We found that the upward flow of sulphate- and oxygen-free Mud volcano fluids restricts the availability of these electron acceptors for methane oxidation, and hence the habitat range of methanotrophs. This mechanism limits the capacity of the microbial methane filter at active Marine Mud volcanoes to
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novel microbial communities of the haakon mosby Mud volcano and their role as a methane sink
Nature, 2006Co-Authors: Marcus Elvert, Helge Niemann, Tina Lösekann, Dirk De Beer, Thierry Nadalig, Katrin Knittel, Rudolf AmannAbstract:SubMarine Mud volcanoes may be major players in the emission of the greenhouse gas methane. A select group of microorganisms, called methanotrophs, can consume this gas, but their impact on methane emission in this environment is not well understood. A study of the waters around a Mud volcano in the Barents Sea has identified three key methanotrophic communities: aerobic bacteria, anaerobic archaea living beneath tubeworms, and previously undescribed archaea associated with bacterial mats. A natural cap on the capacity of the microbial methane filter was also discovered: the upward flow of sulphate- and oxygen-free volcanic fluids restricts the efficiency of methane oxidation, allowing much of the methane to escape to the hydrosphere and potentially the atmosphere. Mud volcanism is an important natural source of the greenhouse gas methane to the hydrosphere and atmosphere1,2. Recent investigations show that the number of active subMarine Mud volcanoes might be much higher than anticipated (for example, see refs 3–5), and that gas emitted from deep-sea seeps might reach the upper mixed ocean6,7,8. Unfortunately, global methane emission from active subMarine Mud volcanoes cannot be quantified because their number and gas release are unknown9. It is also unclear how efficiently methane-oxidizing microorganisms remove methane. Here we investigate the methane-emitting Haakon Mosby Mud Volcano (HMMV, Barents Sea, 72° N, 14° 44′ E; 1,250 m water depth) to provide quantitative estimates of the in situ composition, distribution and activity of methanotrophs in relation to gas emission. The HMMV hosts three key communities: aerobic methanotrophic bacteria (Methylococcales), anaerobic methanotrophic archaea (ANME-2) thriving below siboglinid tubeworms, and a previously undescribed clade of archaea (ANME-3) associated with bacterial mats. We found that the upward flow of sulphate- and oxygen-free Mud volcano fluids restricts the availability of these electron acceptors for methane oxidation, and hence the habitat range of methanotrophs. This mechanism limits the capacity of the microbial methane filter at active Marine Mud volcanoes to <40% of the total flux.
William L Siegmann - One of the best experts on this subject based on the ideXlab platform.
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Geoacoustic Inversion for a New England Mud Patch Sediment Using the Silt-Suspension Theory of Marine Mud
IEEE Journal of Oceanic Engineering, 2020Co-Authors: Elisabeth M Brown, Jason D. Chaytor, William L SiegmannAbstract:This article provides an application of the silt-suspension theory to a Bayesian-inference inversion for the geo-acoustic parameters in Marine Mud. The theory, with consequences that have been developed recently, postulates a suspension of water and clay mineral card-houses that supports moderately dilute concentrations of silt particles. The approach is an example of a physically based model inversion, in which parameters representing physical Mud-layer properties are obtained by inversion and used to produce estimates of geoacoustic properties, including their frequency dependence. The acoustic data are from a combustive source signal propagated along a track, located over several meters of fine-grained Mud in the New England Mud Patch, to a single hydrophone on a receiver array during the 2017 Seabed Characterization Experiment. Data extracted from a nearby piston core inform the physical modeling, with selections of inversion parameters guided by both sensitivity analyses and bounds from archival and core measurements. Results show the feasibility of this inversion approach. The estimates of Mud density and sound speed are close to values obtained independently. The frequency dependence of attenuation is estimated over the full low-frequency source band and has an approximate power exponent of 1.72.
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influence of sand silt particle size distributions on compressional wave attenuation in Marine Mud sediments
Journal of the Acoustical Society of America, 2017Co-Authors: Elisabeth M Brown, Allan D Pierce, William L SiegmannAbstract:High porosity Marine Mud from different sites typically contains different amounts of clay, sand, and silt particles, along with other material. A recent talk [Pierce et al., ASA Honolulu, 5aAO1 (2016)] explored a mechanism for why sand and silt particles in suspension can provide the dominant contributions to the frequency dependence of compressional wave attenuation. The card-house structure of the clay is critical in supporting the particles and keeping them separated. Example calculations for spherical particles of the same size showed physically reasonable attenuation behavior at low and high frequencies. This presentation considers extensions of the approach, particularly accounting for distributions of particle sizes, and emphasizes comparisons of attenuation predictions with available field data. Using reasonable assumptions about the clay volume and the sand and silt distributions, it is possible to estimate the numbers of sand and silt particles, and consequently the attenuation, from the sedime...
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Influence of sand/silt particle size distributions on compressional wave attenuation in Marine Mud sediments
Journal of the Acoustical Society of America, 2017Co-Authors: Elisabeth M Brown, Allan D Pierce, William L SiegmannAbstract:High porosity Marine Mud from different sites typically contains different amounts of clay, sand, and silt particles, along with other material. A recent talk [Pierce et al., ASA Honolulu, 5aAO1 (2016)] explored a mechanism for why sand and silt particles in suspension can provide the dominant contributions to the frequency dependence of compressional wave attenuation. The card-house structure of the clay is critical in supporting the particles and keeping them separated. Example calculations for spherical particles of the same size showed physically reasonable attenuation behavior at low and high frequencies. This presentation considers extensions of the approach, particularly accounting for distributions of particle sizes, and emphasizes comparisons of attenuation predictions with available field data. Using reasonable assumptions about the clay volume and the sand and silt distributions, it is possible to estimate the numbers of sand and silt particles, and consequently the attenuation, from the sedime...
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effect of sand and silt particles on the attenuation of compressional waves in Marine Mud sediments
Journal of the Acoustical Society of America, 2016Co-Authors: Allan D Pierce, William L Siegmann, Elisabeth M BrownAbstract:Mud in Marine sediments is a mixture of clay, sand, and silt particles. Present paper follows up on a suggestion by Holland and Dosso (JASA, 2013) that the variability of the measured frequency-dependent compressional wave attenuation may be caused by the variability of the amounts of sand and silt particles. The premise is that the porosity for the Mud is high and that the sand and silt particles are in suspension. They do not settle out to the bottom of the layer because the card-house fabric of the clay particles tends to hold them in place. This supposition leads to a theory where the clay configuration gives a base-line attenuation, and the contribution from the individual sand and silt particles is additive. The estimation of the latter is distinguished from the existing theories of attenuation of sound in sandy/silty sediments in that the particles are presumed not to touch each other. Particles are assumed to be spherical and there is no slip between particle surfaces and the surrounding water. Ea...
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suspension theory for the effect of silt particles on attenuation of compressional waves in Marine Mud sediments
171st Meeting of the Acoustical Society of America, 2016Co-Authors: Allan D Pierce, William L Siegmann, Elisabeth M BrownAbstract:Mud in Marine sediments is a mixture of clay and silt particles. Paper follows a suggestion by Holland and Dosso (JASA, 2013) that the variability of the measured frequency-dependent compressional wave attenuation may be caused by the variability of the amounts of silt particles. The premise is that the silt particles are in suspension. They do not settle out to the bottom of the layer because the card-house fabric of the clay particles tends to hold them in place. This theory leads to a supposition where the clay configuration gives a negligible base-line attenuation, and the contribution from the individual silt particles is additive. The estimation of the latter is distinguished from the existing theories of attenuation of sound in sandy/silty sediments in that the particles are presumed not to touch each other. Particles are assumed to be spherical and there is no slip between particles and the surrounding water. Earlier formulations of attenuation in suspensions by Lamb (Hydrodynamics) and Urick (JAS...
Lixin Zhang - One of the best experts on this subject based on the ideXlab platform.
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amphibacillus marinus sp nov a member of the genus amphibacillus isolated from Marine Mud
International Journal of Systematic and Evolutionary Microbiology, 2013Co-Authors: Na Yang, Jian Wang, Qian Wang, Benoit Pugin, Lixin ZhangAbstract:A Gram-positive, spore-forming, rod-shaped bacterium, designated J1T was isolated from deep-sea Mud collected from the South China Sea and subjected to polyphasic taxonomic investigation. Phylogenetic analysis based on 16S rRNA gene sequences revealed that J1T clustered with the type strains of Amphibacillus cookii , Amphibacillus sediminis and Amphibacillus jilinensis and exhibited a range of similarity of 93.9–97.0 % to members of the genus Amphibacillus . The DNA G+C content was 36.7 mol%. Chemotaxonomic analysis showed no quinones, and the cell wall contained meso-diaminopimelic acid as the diagnostic diamino acid for strain J1T. The major cellular fatty acids were iso-C15 : 0 and anteiso-C15 : 0. Strain J1T was positive for catalase activity and negative for oxidase activity. On the basis of phylogenetic position and phenotypic properties, strain J1T represents a novel species of the genus Amphibacillus and the name Amphibacillus marinus sp. nov. is proposed. The type strain is J1T ( = CGMCC 1.10434T = JCM 17099T).