Biology subjects

Beaudoin, D.

Publications and source records attributed to Beaudoin, D..

3 recordsLinked to original sources

bioRxiv2023

PCR-based survey of methane-cycling archaea in methane-soaked subsurface sediments of Guaymas Basin, Gulf of California

The Guaymas Basin in the Gulf of California is characterized by active seafloor spreading, rapid deposition of organic-rich sediments, steep geothermal gradients, and abundant methane of mixed thermogenic and microbial origin. Subsurface sediment samples from eight drilling sites with distinct geochemical and thermal profiles were selected for DNA extraction and PCR amplicifation to explore the diversity of methane-cycling archaea in the Guaymas Basin subsurface. We performed PCR amplifications with general (mcrIRD), and ANME-1 specific primers that target the alpha () subunit of methyl coenzyme M reductase (mcrA). Diverse ANME-1 lineages associated with anaerobic methane oxidation were detected in seven out of the eight drilling sites, preferentially around the methane-sulfate interface, and in several cases showed preferences for specific sampling sites. Phylogenetically, most ANME-1 sequences from the Guaymas Basin subsurface were related to marine mud volcanoes, seep sites, and the shallow marine subsurface. The most frequently recovered methanogenic phylotypes were closely affiliated with the hyperthermophilic Methanocaldococcaceae, and found at the hydrothermally influenced Ringvent site. The coolest drilling site, in the northern axial trough of Guaymas Basin, yielded the greatest diversity of methanogen lineages. Our survey indicates potential for extensive microbial methane cycling within subsurface sediments of Guaymas Basin.

microbiology↗

bioRxiv2023

Metagenomic Profiles of Archaea and Bacteria within Thermal and Geochemical Gradients of the Guaymas Basin Deep Subsurface

While the temperature gradients of Earths crust and sediments are thought to delineate the downward extent and ultimate limits of the subsurface biosphere, the actual course of consecutively changing microbial communities and activities, from cool surficial sediments towards the deep, hot biosphere, remains to be charted. We used metagenomic and metatranscriptomic analyses of the hydrothermally heated, massive sediment layers of Guaymas Basin (Gulf of California, Mexico) to examine the environmental distribution and activity patterns of bacteria and archaea along thermal, geochemical and cell count gradients. Composition and distribution of MAGs, dominated by Chloroflexota and Thermoproteota, were shaped by biogeochemical parameters as long as temperatures remained moderate, but downcore increasing temperatures overrode other factors beyond ca. 45{degrees}C. Consistently, MAG genome size and diversity decreased with increasing temperature, indicating a conspicuous downcore winnowing of the subsurface biosphere. In contrast, specific archaeal MAGs within the Thermoproteota and Hadarchaeota increased in relative abundance and in recruitment of transcriptome reads towards deeper, hotter sediments, and mark the transition towards a distinct deep, hot biosphere.

bioinformatics↗

bioRxiv2022

Two canonically aerobic foraminifera express distinct peroxisomal and mitochondrial metabolisms

Certain benthic foraminifera are known to thrive in marine sediments with low oxygen or even without detectable oxygen. Potential survival avenues used by these supposedly aerobic protists include fermentation and anaerobic respiration, although details on their adaptive mechanisms remain somewhat elusive. To better understand the metabolic versatility of foraminifera, we studied two benthic species that thrive in oxygen-depleted marine sediments. Here we detail, via transcriptomics and metatranscriptomics, differential gene expression of Nonionella stella and Bolivina argentea, collected from Santa Barbara Basin, California, USA, in response to varied oxygenation and chemical amendments. Organelle-specific metabolic reconstructions revealed that these two species utilize adaptable mitochondrial and peroxisomal metabolism that reflect their differing lifestyles. N. stella, most abundant in anoxia and characterized by the lack of food vacuoles and the abundance of intracellular lipid droplets, was predicted to couple the putative peroxisomal beta-oxidation and glyoxylate cycle with a versatile electron transport system and a partial TCA cycle running in the reductive direction. In contrast, B. argentea, most abundant in hypoxia and contains food vacuoles, was predicted to utilize the putative peroxisomal gluconeogenesis and a full TCA cycle but lacks the expression of key beta-oxidation and glyoxylate cycle genes. These metabolic adaptations likely confer ecological success while encountering deoxygenation and illuminate the importance of metabolic modifications and interactions between mitochondria and peroxisomes in protists. ImportanceForaminiferan protists are nearly ubiquitous in todays oceans and likely were major components of the Neoproterozoic protistan community. While largely considered aerobic, certain foraminifera demonstrate surprising adaptability to hypoxia and anoxia, contributing to biogeochemical cycling in benthic environments. The analyses of Rhizarian adaptive metabolism set the stage for studying other microeukaryotes under increasing ocean deoxygenation. Revealing the metabolic roles of foraminifera in anaerobic biogeochemical cycling should spur reassessments of existing paleoecological datasets as well as new perspectives on the metabolic evolution of eukaryotic cells.

microbiology↗