Greening, C. | Search bioRxiv

bioRxiv2018

Potential for microbial anaerobic hydrocarbon degradation in naturally occurring petroleum-associated deep-sea sediments

The lack of microbial genomes and isolates from the deep seabed means that very little is known about the ecology of this vast habitat. Here, we investigated energy and carbon acquisition strategies of microbial communities from three deep seabed petroleum seeps (3 km water depth) in the Eastern Gulf of Mexico. Shotgun metagenomic analysis revealed that each sediment harbored diverse communities of chemoheterotrophs and chemolithotrophs. We recovered 82 metagenome-assembled genomes affiliated with 21 different archaeal and bacterial phyla. Multiple genomes encoded enzymes for anaerobic oxidation of aliphatic and aromatic compounds, including those of candidate phyla Aerophobetes, Aminicenantes, TA06 and Bathyarchaeota. Microbial interactions are predicted to be driven by acetate and molecular hydrogen. These findings are supported by sediment geochemistry, metabolomics, and thermodynamic modelling. Overall, we infer that deep-sea sediments experiencing thermogenic hydrocarbon inputs harbor phylogenetically and functionally diverse communities potentially sustained through anaerobic hydrocarbon, acetate and hydrogen metabolism.

microbiology↗

bioRxiv2016

Mitochondrial-nuclear interactions maintain a deep mitochondrial split in the face of nuclear gene flow

Metabolic processes in eukaryotic cells depend on interactions between mitochondrial and nuclear gene products (mitonuclear interactions). These interactions could play a direct role in population divergence. We studied the evolution of mitonuclear interactions in a widespread passerine that experienced population divergence followed by bi-directional mitochondrial introgression into different nuclear backgrounds. Using >60,000 SNPs, we quantified patterns of nuclear genetic differentiation between populations that occupy different climates and harbour deeply divergent mitolineages despite ongoing nuclear gene flow. Analyses were performed independently for two sampling transects intersecting mitochondrial divergence in different nuclear backgrounds. In both transects, low genome-wide nuclear differentiation was accompanied by strong differentiation at a ~15.4 Mb region of chromosome 1A. This region is enriched for genes performing mitochondrial functions. Molecular signatures of selective sweeps in this region alongside those in the mitochondrial genome suggest a history of adaptive mitonuclear co-introgression. The chromosome 1A region has elevated linkage disequilibrium, suggesting that selection on genomic architecture may favour low recombination among nuclear-encoded genes with mitochondrial functions. In this system, mitonuclear interactions appear to maintain the geographic separation of two mitolineages in the face of nuclear gene flow, supporting mitonuclear co-evolution as an important vehicle for climatic adaptation and population divergence.

evolutionary biology↗