Phylogenetic and functional diverse ANME-1 thrive in Arctic hydrothermal vents.

The methane-rich areas, the Loki's Castle vent field and the Jan Mayen vent field at the Arctic Mid Ocean Ridge (AMOR), host abundant niches for anaerobic methane-oxidizers, which are predominantly filled by members of the ANME-1. In this study, we used a metagenomic-based approach that revealed the presence of phylogenetic and functional different ANME-1 subgroups at AMOR, with heterogeneous distribution. Based on a common analysis of ANME-1 genomes from AMOR and other geographic locations, we observed that AMOR subgroups clustered with a vent-specific ANME-1 group that occurs solely at vents, and with a generalist ANME-1 group, with a mixed environmental origin. Generalist ANME-1 are enriched in genes coding for stress response and defense strategies, suggesting functional diversity among AMOR subgroups. ANME-1 encode a conserved energy metabolism, indicating strong adaptation to sulfate-methane-rich sediments in marine systems, which does not however prevent global dispersion. A deep branching family named Ca. Veteromethanophagaceae was identified. The basal position of vent-related ANME-1 in phylogenomic trees suggests that ANME-1 originated at hydrothermal vents. The heterogeneous and variable physicochemical conditions present in diffuse venting areas of hydrothermal fields could have favored the diversification of ANME-1 into lineages that can tolerate geochemical and environmental variations.

Discovery of a Thermostable GH10 Xylanase with Broad Substrate Specificity from the Arctic Mid-Ocean Ridge Vent System.

A two-domain GH10 xylanase-encoding gene (amor_gh10a) was discovered from a metagenomic data set, generated after in situ incubation of a lignocellulosic substrate in hot sediments on the sea floor of the Arctic Mid-Ocean Ridge (AMOR). AMOR_GH10A comprises a signal peptide, a carbohydrate-binding module belonging to a previously uncharacterized family, and a catalytic glycosyl hydrolase (GH10) domain. The enzyme shares the highest sequence identity (42%) with a hypothetical protein from a Verrucomicrobia bacterium, and its GH10 domain shares low identity (24 to 28%) with functionally characterized xylanases. Purified AMOR_GH10A showed thermophilic and halophilic properties and was active toward various xylans. Uniquely, the enzyme showed high activity toward amorphous cellulose, glucomannan, and xyloglucan and was more active toward cellopentaose than toward xylopentaose. Binding assays showed that the N-terminal domain of this broad-specificity GH10 binds strongly to amorphous cellulose, as well as to microcrystalline cellulose, birchwood glucuronoxylan, barley ß-glucan, and konjac glucomannan, confirming its classification as a novel CBM (CBM85).IMPORTANCE Hot springs at the sea bottom harbor unique biodiversity and are a promising source of enzymes with interesting properties. We describe the functional characterization of a thermophilic and halophilic multidomain xylanase originating from the Arctic Mid-Ocean Ridge vent system, belonging to the well-studied family 10 of glycosyl hydrolases (GH10). This xylanase, AMOR_GH10A, has a surprisingly wide substrate range and is more active toward cellopentaose than toward xylopentaose. This substrate promiscuity is unique for the GH10 family and could prove useful in industrial applications. Emphasizing the versatility of AMOR_GH10A, its N-terminal domain binds to both xylans and glycans, while not showing significant sequence similarities to any known carbohydrate-binding module (CBM) in the CAZy database. Thus, this N-terminal domain lays the foundation for the new CBM85 family.

Examination of the Metamax I and II oxygen analysers during exercise studies in the laboratory.

The performance of the Metamax I and the Metamax II portable analysers for measuring the O2 uptake has been examined during exercise. Healthy subjects ran on the treadmill or bicycled on ergometers while the O2 uptake was measured by the Metamaxes and also by the Douglas bag technique or the Vmax 29 instrument. In the first series of experiments, O2 uptake was measured by each instrument in turn. In later experiments two or more breathing valves were connected in a series, thus enabling measurement of the O2 uptake simultaneously by more than one instrument. The O2 uptake measured by the Metamax analysers rose linearly by the value given by the control methods. However, there were variations of approximately 5% because the relationships differed between subjects. When the data from each subject were examined separately, the error of regression was 0.5-1 micromol s(-1) kg(-1) (2-3%), and the error of regression when relating the O2 uptake to the exercise intensity was similar to that found when using the Douglas bag technique alone. In most cases the lung ventilation reported by the Metamaxes was a few percent less than that given by the control methods, while the fractional extraction of O2 was higher for the Metamaxes. The respiratory exchange ratios (R-value) reported by the Metamaxes were in good agreement with those of the control methods in the range 0.9-1.0 only; for this parameter, the Metamaxes do not seem to be reliable for exercise testing. The O2 uptake and the R-value were also calculated from the raw data reported by the Metamaxes. The calculated values differed somewhat from those reported by the instruments, and the calculated values were more in agreement with those obtained by the Douglas bag technique than those reported by the instrument. This study suggests that the O2 uptake reported by the Metamaxes is precisely measured within subjects but that there are some systematic errors as well as variations between subjects.