Within the endemic invertebrate faunas of hydrothermal vents, five biogeographic provinces are recognized. Invertebrates at two Indian Ocean vent fields (Kairei and Edmond) belong to a sixth province, despite ecological settings and invertebrate-bacterial symbioses similar to those of both western Pacific and Atlantic vents. Most organisms found at these Indian Ocean vent fields have evolutionary affinities with western Pacific vent faunas, but a shrimp that ecologically dominates Indian Ocean vents closely resembles its Mid-Atlantic counterpart. These findings contribute to a global assessment of the biogeography of chemosynthetic faunas and indicate that the Indian Ocean vent community follows asymmetric assembly rules biased toward Pacific evolutionary alliances.

Background: DNA damage leads to cellular responses that include the increased expression of DNA repair genes, repression of DNA replication and alterations in cellular metabolism. Archaeal information processing pathways resemble those in eukaryotes, but archaeal damage response pathways remain poorly understood.

(optimum at 70 SC). Both strains grew fastest at 2 5 % (w/v) NaCl and at pH 6, although growth was observed from pH 4 7 to pH 7 5. EX-H1 T and EX-H2 T were able to use elemental sulfur, thiosulfate or hydrogen as an electron donor, and oxygen (2-3 %, v/v) or nitrate as an electron acceptor. EX-H1 T was also able to use elemental sulfur as an electron acceptor. EX-H1 T and EX-H2T further differed in their genomic GMC content (38 5 and 37 4 mol %, respectively) and 16S rRNA sequences (4 % difference). Maximum-likelihood analysis of the 16S rRNA phylogeny placed both isolates within the Aquificales as a distinct lineage and showed them to be only about 85 % similar to Aquifex pyrophilus. On the basis of phenotypic and phylogenetic characteristics, it is proposed that EX-H1 T and EX-H2 T belong to a new genus within the Aquificales, namely Persephonella gen. nov. It is further proposed that EX-H1 T be named Persephonella marina sp. nov., the type species of the genus, and that EX-H2 T be named Persephonella guaymasensis sp. nov., a second species in this genus.

Consortia containing a novel coccus-shaped, anaerobic heterotroph together with Pyrobaculum rods were cultivated from geothermal environments in New Zealand. Pure cultures of the cocci were only obtained from one such consortium, despite extensive attempts. Cells of this strain (AQ1.S1 T ) were regular to irregular cocci in morphology and occasionally formed large aggregates, especially when utilizing polysaccharides such as konjac glucomannan as a carbon source. Strain AQ1.S1 T is a hyperthermophile, with an optimal temperature for growth between 92 and 95 6C (range 85-98 6C), and a moderate acidophile, with optimal growth occurring at pH 6?4 (range 5?4-7?0). Growth was inhibited by the addition of sulphur and NaCl (optimal growth occurred without addition of NaCl) and an electron acceptor was not required. Strain AQ1.S1T utilized starch, trypticase peptone, lactose, glucose, konjac glucomannan, mannose, galactose, maltose, glycogen and b-cyclodextrin as carbon sources. The G+C content was 52?9 mol%. Based on 16S rRNA gene sequence analysis and physiological features it is proposed that isolate AQ1.S1 T (=DSM 17230represents the type strain of a novel species of a new genus within the Crenarchaeota, Ignisphaera aggregans gen. nov., sp. nov.

The putative L-haloacid dehalogenase gene (DehRhb) from a marine Rhodobacteraceae family was cloned and overexpressed in Escherichia coli. The DehRhb protein was shown to be an L-haloacid dehalogenase with highest activity towards brominated substrates with short carbon chains ( C3). The optimal temperature for enzyme activity was 55°C, and the V max and K m were 1.75 lMÁmin À1 Ámg À1 of protein and 6.72 mM, respectively, when using monobromoacetic acid as a substrate. DehRhb showed moderate thermal stability, with a melting temperature of 67°C. The enzyme demonstrated high tolerance to solvents, as shown by thermal shift experiments and solvent incubation assays. The DehRhb protein was crystallized and structures of the native, reaction intermediate and substrate-bound forms were determined. The active site of DehRhb had significant differences from previously studied L-haloacid dehalogenases. The asparagine and arginine residues shown to be essential for catalytic activity in other L-haloacid dehalogenases are not present in DehRhb. The histidine residue which replaces the asparagine residue in DehRhb was coordinated by a conformationally strained glutamate residue that replaces a conserved glycine. The His/Glu dyad is positioned for deprotonation of the catalytic water which attacks the ester bond in the reaction intermediate. The catalytic water in DehRhb is shifted by~1.5 A from its position in other L-haloacid dehalogenases. A similar His/Glu or Asp dyad is known to activate the catalytic water in haloalkane dehalogenases. The DehRhb enzyme represents a novel member within the L-haloacid dehalogenase family and it has potential to be used as a commercial biocatalyst. DatabaseThe coordinates and structure factors of the crystal structures have been deposited in the Protein Data Bank with the codes 2yml, 2ymm, 2ymp, 2ymq and 2yn4. Nucleotide sequence data has been deposited in the GenBank database under the accession number JX868516.

SummaryThe nucleotide excision repair (NER) pathway removes bulky lesions such as photoproducts from DNA. In both bacteria and eukarya, lesions located in transcribed strands are repaired significantly faster than those located in non-transcribed strands due to damage signalling by stalled RNA polymerase molecules: a phenomenon known as transcriptioncoupled repair (TCR). TCR requires a mechanism for coupling the detection of stalled RNA polymerase molecules to the NER pathway, provided in bacteria by the Mfd protein. In the third domain of life, archaea, the pathway of NER is not well defined, there are no Mfd homologues and the existence of TCR has not been investigated. In this report we looked at rates of removal of photoproducts in three different operons of the crenarchaeon Sulfolobus solfataricus following UV irradiation. We found no evidence for significantly faster repair in the transcribed strands of these three operons. The rate of global genome repair in S. solfataricus is relatively rapid, and this may obviate the requirement for a specialized TCR pathway. Significantly faster repair kinetics were observed in the presence of visible light, consistent with the presence of a gene for photolyase in the genome of S. solfataricus.

Stable carbon isotopes can provide insight into carbon cycling pathways in natural environments. We examined carbon isotope fractionations associated with a hyperthermophilic fermentative bacterium, Thermotoga maritima, and a thermophilic chemolithoautotrophic bacterium Persephonella marina. In T. maritima, phospholipid fatty acids (PLFA) are slightly enriched in 13C relative to biomass (epsilon = 0.1-0.8 per thousand). However, PLFA and biomass are depleted in 13C relative to the substrate glucose by approximately 8 per thousand. In P. marina, PLFA are 1.8-14.5 per thousand enriched in 13C relative to biomass, which suggests that the reversed tricarboxylic acid (TCA) cycle or the 3-hydroxypropionate pathway may be used for CO2 fixation. This is supported by small fractionation between biomass and CO2 (epsilon = -3.8 per thousand to -5.0 per thousand), which is similar to fractionations reported for other organisms using similar CO2 fixation pathways. Identification of the exact pathway will require biochemical assay for specific enzymes associated with the reversed TCA cycle or the 3-hydroxypropionate pathway.

We review and update the work on genetic elements, e.g., viruses and plasmids (exluding IS elements and transposons) in the kingdom Crenarchaeota (Thermoproteales and Sulfolobales) and the orders Thermococcales and Thermoplasmales in the kingdom Euryarchaeota of the archael domain, including unpublished data from our laboratory. The viruses of Crenarchaeota represent four novel virus families. The Fuselloviridae represented by SSVI of S. shibatae and relatives in other Sulfolobus strains have the form of a tailed spindle. The envelope is highly hydrophobic. The DNA is double-stranded and circular. Members of this group have also been found in Methanococcus and Haloarcula. The Lipothrivciridae (e.g., T TV1 to 3) have the form of flexible filaments. They have a core containing linear double-stranded DNA and DNA-binding proteins which is wrapped into a lipid membrane. The "Bacilloviridae" (e.g., TTV4 and SIRV) are stiff rods lacking this membrane, but also featuring linear double-stranded DNA and DNA-binding proteins. Both virus types carry on both ends structures involved in the attachment to receptors. Both types are represented in Thermoproteus and Sulfolobus. The droplet-formed novel Sulfolobus virus SNDV represents the "Guttaviridae" containing circular double-stranded DNA. Though head and tail viruses distantly resembling T phages or lambdoid phages were seen electronmicroscopically in solfataric water samples, no such virus has so far been isolated. SSV1 is temperate, TTV1 causes lysis after induction, the other viruses found so far exist in carrier states. The hosts of all but TTV1 survive virus production. We discuss the implications of the nature of these viruses for understanding virus evolution. The plasmids found so far range in size from 4.5 kb to about 40 kb. Most of them occur in high copy number, probably due to the way of their detection. Most are cryptic, pNOB8 is conjugative, the widespread pDL10 alleviates in an unknown way autotrophic growth of its host Desulfurolobus by sulfur reduction. The plasmid pTIK4 appears to encode a killer function. pNOB8 has been used as a vector for the transfer of the lac S (beta-galactosidase) gene into a mutant of S. solfataricus.