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Research Articles

India - Andaman Islands, India
Cesiribacter andamanensis

South Tonga Arc
Fe-oxidizing bacteria - metabolize Iron (Fe)
Fe-rich hydrothermal sediments at two South Tonga Arc submarine volcanoes.

New Zealand: Kermadec Arc.
Fe-oxidizing bacterium 'Mariprofundus ferrooxydans'
iron-containing flocculent mats associated with submarine volcanoes along the Kermadec Arc

Eastern Mediterranean
(Nile Deep Sea Fan, Eastern Mediterranean).
iron sulfur
related to 'Ca. Arcobacter sulfidicus'
similar neutrophilic Fe(II)-oxidizing betaproteobacterium Leptothrix ochracea
Biogeochemistry and community composition of iron- and sulfur-precipitating microbial mats at the Chefren mud volcano (Nile Deep Sea Fan, Eastern Mediterranean).

Prokaryotic active submarine mud volcano (Kazan mud volcano, East Mediterranean Sea).
Gammaproteobacteria
anaerobic oxidation of methane

methane oxidizers at the underwater Haakon Mosby Mud Volcano, Barents Sea.
Methylobacter and Methylophaga species in the active volcano
tubeworms (Siboglinidae, formerly known as Pogonophora)
Beggiatoa species
The HMMV 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)

Cesiribacter andamanensis gen. nov., sp. nov., a novel bacterium isolated from a soil sample of a mud volcano, Andaman Islands, India.
[Int J Syst Evol Microbiol. 2010 Jul 23. [Epub ahead of print] ]
Srinivas TN, Kumar PA, Madhu S, Sunil B, Sharma TV, Shivaji S.

A novel Gram-staining-negative, rod shaped, non-motile bacterium, strain AMV16T, was isolated from a soil sample collected from a mud volcano located in the Andaman Islands, India. The cell suspension was pale orange. Cells of the strain AMV16T were positive for catalase, oxidase, lipase, ornithine decarboxylase and lysine decarboxylase and negative for gelatinase and urease. The fatty acids were dominated by saturated fatty acids (62.3%), with a high abundance of saturated fatty acids of C15:0 (28.7%), anteiso-C14:0 (15.1%), and unsaturated fatty acids of C16:1 omega9c (23.9%) and C18:1 omega9c (13.8%). Strain AMV16T contained MK-4 and MK-7 as the major respiratory quinones and diphosphatidylglycerol and phosphatidylethanolamine make up the phospholipid composition. The G + C content of DNA of the strain AMV16T was 50.9 mol%. The BLAST sequence similarity search based on 16S rRNA gene sequence indicated that species of the genus 'Marivirga' were the nearest phylogenetic neighbors with a pairwise sequence similarity ranging from 89.9 to 90.0%. The phylogenetic analyses indicated that the strain AMV16T clustered with 'Marivirga tractuosa' along with 'Marivirga sericea' with a phylogenetic distance of 85.4% respectively, distinct from the clades represented by the other genera of the family 'Flammeovirgaceae'. Based on the above mentioned phenotypic and phylogenetic characteristics, strain AMV16T is proposed as the representative of a novel genus and a new species, Cesiribacter andamanensis gen. nov., sp. nov. The type strain of Cesiribacter andamanensis gen. nov., sp. nov., is AMV16T (=DSM 22818T = CCUG 58431T).. Read more ...

South Tonga Arc submarine volcanoes
Zetaproteobacteria - iron (Fe) oxidizers

Bacterial diversity in Fe-rich hydrothermal sediments at two South Tonga Arc submarine volcanoes.
[Geobiology. 2010 Jun 1. [Epub ahead of print]]
Forget NL, Murdock SA, Juniper SK.
Department of Biology, University of Victoria, Petch Building 116, 3800 Finnerty Rd, Victoria, BC, Canada V8P 5C2.

Abstract Seafloor iron oxide deposits are a common feature of submarine hydrothermal systems. Morphological study of these deposits has led investigators to suggest a microbiological role in their formation, through the oxidation of reduced Fe in hydrothermal fluids. South Tonga Arc submarine volcanoes, have been isolated from a few of these deposits but generally little is known about the microbial diversity associated with this habitat. In this study, we characterized bacterial diversity in two Fe oxide samples collected on the seafloor of Volcanoes 1 and 19 on the South Tonga Arc. We were particularly interested in confirming the presence of Zetaproteobacteria at these two sites and in documenting the diversity of groups other than Fe oxidizers. Our results (small subunit rRNA gene sequence data) showed a surprisingly high bacterial diversity, with 150 operational taxonomic units belonging to 19 distinct taxonomic groups. Both samples were dominated by Zetaproteobacteria Fe oxidizers. This group was most abundant at Volcano 1, where sediments were richer in Fe and contained more crystalline forms of Fe oxides. Other groups of bacteria found at these two sites include known S- and a few N-metabolizing bacteria, all ubiquitous in marine environments. The low similarity of our clones with the GenBank database suggests that new species and perhaps new families were recovered. The results of this study suggest that Fe-rich hydrothermal sediments, while dominated by Fe oxidizers, can be exploited by a variety of autotrophic and heterotrophic micro-organisms.

Kermadec Arc north of New Zealand
Fe-oxidizing bacterium Mariprofundus ferrooxydan

Molecular comparison of bacterial communities within iron-containing flocculent mats associated with submarine volcanoes along the Kermadec Arc.
[Appl Environ Microbiol. 2009 Mar;75(6):1650-7. Epub 2008 Dec 29.]
Hodges TW, Olson JB.
Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA.

Iron oxide sheaths and filaments are commonly found in hydrothermal environments and have been shown to have a biogenic origin. These structures were seen in the flocculent material associated with two submarine volcanoes along the Kermadec Arc north of New Zealand. Molecular characterization of the bacterial communities associated with the flocculent samples indicated that no known Fe-oxidizing bacteria dominated the recovered clone libraries. However, clones related to the recently described Fe-oxidizing bacterium Mariprofundus ferrooxydans were obtained from both the iron-containing flocculent (Fe-floc) and sediment samples, and peaks corresponding to Mariprofundus ferrooxydans, as well as the related clones, were observed in several of our terminal restriction fragment length polymorphism profiles. A large group of epsilonproteobacterial sequences, for which there is no cultured representative, dominated clones from the Fe-floc libraries and were less prevalent in the sediment sample. Phylogenetic analyses indicated that several operational taxonomic units appeared to be site specific, and statistical analyses of the clone libraries found that all samples were significantly different from each other. Thus, the bacterial communities in the Fe-floc samples were not more closely related to each other than to the sediment communities..

Chefren mud volcano (Nile Deep Sea Fan, Eastern Mediterranean).
sulfide-oxidizing epsilonproteobacterium "Candidatus Arcobacter sulfidicus."
Fe(II)-oxidizing betaproteobacterium Leptothrix ochracea.

Biogeochemistry and community composition of iron- and sulfur-precipitating microbial mats at the Chefren mud volcano (Nile Deep Sea Fan, Eastern Mediterranean).
[Appl Environ Microbiol. 2008 May;74(10):3198-215. Epub 2008 Mar 31.]
Omoregie EO, Mastalerz V, de Lange G, Straub KL, Kappler A, Røy H, Stadnitskaia A, Foucher JP, Boetius A.
Max Planck Institute for Marine Microbiology, Bremen, Germany.

In this study we determined the composition and biogeochemistry of novel, brightly colored, white and orange microbial mats at the surface of a brine seep at the outer rim of the Chefren mud volcano. These mats were interspersed with one another, but their underlying sediment biogeochemistries differed considerably. Microscopy revealed that the white mats were granules composed of elemental S filaments, similar to those produced by the sulfide-oxidizing epsilonproteobacterium "Candidatus Arcobacter sulfidicus." Fluorescence in situ hybridization indicated that microorganisms targeted by a "Ca. Arcobacter sulfidicus"-specific oligonucleotide probe constituted up to 24% of the total the cells within these mats. Several 16S rRNA gene sequences from organisms closely related to "Ca. Arcobacter sulfidicus" were identified. In contrast, the orange mat consisted mostly of bright orange flakes composed of empty Fe(III) (hydr)oxide-coated microbial sheaths, similar to those produced by the neutrophilic Fe(II)-oxidizing betaproteobacterium Leptothrix ochracea. None of the 16S rRNA gene sequences obtained from these samples were closely related to sequences of known neutrophilic aerobic Fe(II)- oxidizing bacteria. The sediments below both types of mats showed relatively high sulfate reduction rates (300 nmol x cm(- 3) x day(-1)) partially fueled by the anaerobic oxidation of methane (10 to 20 nmol x cm(-3) x day(-1)). Free sulfide produced below the white mat was depleted by sulfide oxidation within the mat itself. Below the orange mat free Fe(II) reached the surface layer and was depleted in part by microbial Fe(II) oxidation. Both mats and the sediments underneath them hosted very diverse microbial communities and contained mineral precipitates, most likely due to differences in fluid flow patterns.

iron-reducing bacteria

Environmental processes mediated by iron-reducing bacteria.
[Curr Opin Biotechnol. 1996 Jun;7(3):287-94.]
Fredrickson JK, Gorby YA.
Pacific Northwest National Laboratory, Washington 99352, USA. jk-

Considerable progress has been made towards enhancing our understanding of the phylogeny, ecology and biogeochemical role of dissimilatory iron-reducing bacteria. The known phylogenetic range of iron-reducing bacteria has expanded considerably, as has the known range of iron minerals that serve as a source of Fe(III) for anaerobic respiration. In addition, the number of biotechnological applications of iron-reducing bacteria, including remediation of soils and sediments contaminated with metals, radionuclides and organics, is rapidly expanding.

Kazan mud volcano, East Mediterranean Sea
Gammaproteobacteria

methane oxidizers at the underwater Haakon Mosby Mud Volcano, Barents Sea.
Methylobacter and Methylophaga species in the active volcano
tubeworms (Siboglinidae, formerly known as Pogonophora)
Beggiatoa species

Prokaryotic community structure and diversity in the sediments of an active submarine mud volcano (Kazan mud volcano, East Mediterranean Sea).
[FEMS Microbiol Ecol. 2010 Jun;72(3):429-44. Epub 2010 Mar 3.]
Pachiadaki MG, Lykousis V, Stefanou EG, Kormas KA.
Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Voutes-Heraklion, Greece.

We investigated 16S rRNA gene diversity at a high sediment depth resolution (every 5 cm, top 30 cm) in an active site of the Kazan mud volcano, East Mediterranean Sea. A total of 242 archaeal and 374 bacterial clones were analysed, which were attributed to 38 and 205 unique phylotypes, respectively (> or = 98% similarity). Most of the archaeal phylotypes were related to ANME-1, -2 and -3 members originating from habitats where anaerobic oxidation of methane (AOM) occurs, although they occurred in sediment layers with no apparent AOM (below the sulphate depletion depth). Proteobacteria were the most abundant and diverse bacterial group, with the Gammaproteobacteria dominating in most sediment layers and these were related to phylotypes involved in methane cycling. The Deltaproteobacteria included several of the sulphate-reducers related to AOM. The rest of the bacterial phylotypes belonged to 15 known phyla and three unaffiliated groups, with representatives from similar habitats. Diversity index H was in the range 0.56-1.73 and 1.47-3.82 for Archaea and Bacteria, respectively, revealing different depth patterns for the two groups. At 15 and 20 cm below the sea floor, the prokaryotic communities were highly similar, hosting AOM-specific Archaea and Bacteria. Our study revealed different dominant phyla in proximate sediment layers.

Novel microbial communities of the Haakon Mosby mud volcano and their role as a methane sink.
[Nature. 2006 Oct 19;443(7113):854-8.]
Niemann H, Lösekann T, de Beer D, Elvert M, Nadalig T, Knittel K, Amann R, Sauter EJ, Schlüter M, Klages M, Foucher JP, Boetius A.
Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany.

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 <40% of the total flux.

Haakon Mosby Mud Volcano, Barents Sea

methane oxidizers at the underwater Haakon Mosby Mud Volcano, Barents Sea.
Methylobacter and Methylophaga species in the active volcano
tubeworms (Siboglinidae, formerly known as Pogonophora)
Beggiatoa species

Diversity and abundance of aerobic and anaerobic methane oxidizers at the Haakon Mosby Mud Volcano, Barents Sea.
[Appl Environ Microbiol. 2007 May;73(10):3348-62. Epub 2007 Mar 16.]
Lösekann T, Knittel K, Nadalig T, Fuchs B, Niemann H, Boetius A, Amann R.
Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany.

Submarine mud volcanoes are formed by expulsions of mud, fluids, and gases from deeply buried subsurface sources. They are highly reduced benthic habitats and often associated with intensive methane seepage. In this study, the microbial diversity and community structure in methane-rich sediments of the Haakon Mosby Mud Volcano (HMMV) were investigated by comparative sequence analysis of 16S rRNA genes and fluorescence in situ hybridization. In the active volcano center, which has a diameter of about 500 m, the main methane-consuming process was bacterial aerobic oxidation. In this zone, aerobic methanotrophs belonging to three bacterial clades closely affiliated with Methylobacter and Methylophaga species accounted for 56%+/-8% of total cells. In sediments below Beggiatoa mats encircling the center of the HMMV, methanotrophic archaea of the ANME-3 clade dominated the zone of anaerobic methane oxidation. ANME-3 archaea form cell aggregates mostly associated with sulfate-reducing bacteria of the Desulfobulbus (DBB) branch. These ANME-3/DBB aggregates were highly abundant and accounted for up to 94%+/-2% of total microbial biomass at 2 to 3 cm below the surface. ANME-3/DBB aggregates could be further enriched by flow cytometry to identify their phylogenetic relationships. At the outer rim of the mud volcano, the seafloor was colonized by tubeworms (Siboglinidae, formerly known as Pogonophora). Here, both aerobic and anaerobic methane oxidizers were found, however, in lower abundances. The level of microbial diversity at this site was higher than that at the central and Beggiatoa species-covered part of the HMMV. Analysis of methyl-coenzyme M-reductase alpha subunit (mcrA) genes showed a strong dominance of a novel lineage, mcrA group f, which could be assigned to ANME-3 archaea. Our results further support the hypothesis of Niemann et al. (54), that high methane availability and different fluid flow regimens at the HMMV provide distinct niches for aerobic and anaerobic methanotrophs.

Observational evidence for volcanic impact on sea level and the global water cycle. [Proc Natl Acad Sci U S A. 2007 Dec 11;104(50):19730-4. Epub 2007 Dec 3.]
Grinsted A, Moore JC, Jevrejeva S.
Arctic Centre, University of Lapland, PL122, 96101 Rovaniemi, Finland.

It has previously been noted that there are drops in global sea level (GSL) after some major volcanic eruptions. However, observational evidence has not been convincing because there is substantial variability in the global sea level record over periods similar to those at which we expect volcanoes to have an impact. To quantify the impact of volcanic eruptions we average monthly GSL data from 830 tide gauge records around five major volcanic eruptions. Surprisingly, we find that the initial response to a volcanic eruption is a significant rise in sea level of 9 +/- 3 mm in the first year after the eruption. This rise is followed by a drop of 7 +/- 3 mm in the period 2-3 years after the eruption relative to preeruption sea level. These results are statistically robust and no particular volcanic eruption or ocean region dominates the signature we find. Neither the drop nor especially the rise in GSL can be explained by models of lower oceanic heat content. We suggest that the mechanism is a transient disturbance of the water cycle with a delayed response of land river runoff relative to ocean evaporation and global precipitation that affects global sea level. The volcanic impact on the water cycle and sea levels is comparable in magnitude to that of a large El Niño-La Niña cycle, amounting to approximately 5% of global land precipitation.