Newly discovered Asgard archaea Hermodarchaeota potentially degrade alkanes and aromatics via alkyl/benzyl-succinate synthase and benzoyl-CoA pathway.

Asgard archaea are widely distributed in anaerobic environments. Previous studies revealed the potential capability of Asgard archaea to utilize various organic substrates including proteins, carbohydrates, fatty acids, amino acids and hydrocarbons, suggesting that Asgard archaea play an important role in sediment carbon cycling. Here, we describe a previously unrecognized archaeal phylum, Hermodarchaeota, affiliated with the Asgard superphylum. The genomes of these archaea were recovered from metagenomes generated from mangrove sediments, and were found to encode alkyl/benzyl-succinate synthases and their activating enzymes that are similar to those identified in alkane-degrading sulfate-reducing bacteria. Hermodarchaeota also encode enzymes potentially involved in alkyl-coenzyme A and benzoyl-coenzyme A oxidation, the Wood-Ljungdahl pathway and nitrate reduction. These results indicate that members of this phylum have the potential to strictly anaerobically degrade alkanes and aromatic compounds, coupling the reduction of nitrate. By screening Sequence Read Archive, additional genes encoding 16S rRNA and alkyl/benzyl-succinate synthases analogous to those in Hermodarchaeota were identified in metagenomic datasets from a wide range of marine and freshwater sediments. These findings suggest that Asgard archaea capable of degrading alkanes and aromatics via formation of alkyl/benzyl-substituted succinates are ubiquitous in sediments.

Human activities can drive sulfate-reducing bacteria community in Chinese intertidal sediments by affecting metal distribution.

Sulfate-reducing bacteria (SRB), which are ubiquitous in intertidal sediments, play an important role in global sulfur and carbon cycles, and in the bioremediation of toxic metalloids/metals. Pollution from human activities is now a major challenge to the sustainable development of the intertidal zone, but little is known about how and to what extent various anthropic and/or natural factors affect the SRB community. In the current study, based on the dsrB gene, we investigated the SRB community in intertidal sediment along China's coastline. The results showed that dsrB gene abundances varied among different sampling sites, with the highest average abundance of SRB at XHR (near the Bohai Sea). The SRB community structures showed obvious spatial distribution patterns with latitude along the coastal areas of China, with Desulfobulbus generally being the dominant genus. Correlation analysis and redundancy discriminant analysis revealed that total organic carbon (TOC) and pH were significantly correlated with the richness of the SRB community, and salinity, pH, sulfate and climatic parameters could be the important natural factors influencing the composition of the SRB community. Moreover, metals, especially bioavailable metals, could regulate the diversity and composition of the SRB communities. Importantly, according to structural equation model (SEM) analysis, anthropic factors (e.g., population, economy and industrial activities) could drive SRB community diversity directly or by significantly affecting the concentrations of metals. This study provides the first comprehensive investigation of the direct and indirect anthropic factors on the SRB community in intertidal sediments on a continental scale.

[Distribution of matrix-bound phosphine in surface sediments of Jinpu Bay].

This work investigated the distribution of matrix-bound phosphine in surface sediments of Jinpu Bay and associated environmental factors in summer, using the gas chromatography combined with a pulsed flame detector (GC-PFPD). It showed that phosphine ubiquitously presented in the sediments of Jinpu Bay. Contents of matrix-bound phosphine varied between 62. 58 and 190. 81 ng.kg-1, with the average value of 114.42 ng.kg-1. In addition, the spatial distribution of matrix-bound phosphine indicated that matrix-bound phosphine in inshore sediments had relatively higher contents than those in offshore sediments. Statistical analysis showed that matrix-bound phosphine significantly related to organic phosphorus and alkaline phosphatase activity ( R = 0. 882, P = 0. 01; R = 0. 819, P =0. 023). However, there were no correlations between matrix-bound phosphine and organic nitrogen, inorganic phosphorus and sediment grain sizes. These results implied that accumulation and distribution of matrix-bound phosphined were mainly affected by the decomposition of organic phosphorus by microorganisms.

[Distributions of matrix-bound phosphine in surface sediments of the Yangtze Estuary].

Concentrations of matrix-bound phosphine (MBP) in the surface sediments of the Yangtze Estuary were investigated in the present study using gas chromatography coupled with a pulsed flame photometric detector (GC-PFPD), and the potential environmental factors were discussed. It was shown that the MBP concentrations were relatively higher in May than in November, with the ranges of 139-426 ng x kg(-1) and 111-192 ng x kg(-1), respectively. Also, there was the significant spatial difference in MBP concentrations at the study area. In addition, it was observed that MBP was significantly related to TP, IP, OP, pH, and activities of APA in the surface sediments. However, no significant correlations were found between MBP, organic carbon and salinity.