Relative Abundance and Diversity of Bacterial Methanotrophs at the Oxic–Anoxic Interface of the Congo Deep-Sea Fan

Abstract

Sitting at ∼5,000 m water depth on the Congo-Angola margin and ∼760 km offshore of the West African coast, the recent lobe complex of the Congo deep-sea fan receives large amounts of fluvial sediments (3–5% organic carbon). This organic-rich sedimentation area harbors habitats with chemosynthetic communities similar to those of cold seeps. In this study, we investigated relative abundance, diversity and distribution of aerobic methane-oxidizing bacteria (MOB) communities at the oxic–anoxic interface of sedimentary habitats by using fluorescence in situ hybridization and comparative sequence analysis of particulate mono-oxygenase (pmoA) genes. Our findings revealed that sedimentary habitats of the recent lobe complex hosted type I and type II MOB cells and comparisons of pmoA community compositions showed variations among the different organic-rich habitats. Furthermore, the pmoA lineages were taxonomically more diverse compared to methane seep environments and were related to those found at cold seeps. Surprisingly, MOB phylogenetic lineages typical of terrestrial environments were observed at such water depth. In contrast, MOB cells or pmoA sequences were not detected at the previous lobe complex that is disconnected from the Congo River inputs.

Aliphatic hydrocarbons and triterpenes of the Congo deep-sea fan

“…However, these alkanes were more abundant than their odd counterparts in many samples where UCM cannot be quantified. The last likely sources expected to yield a broad repartition of short-chain alkanes are soil bacteria, shown to contribute to alive microbial communities of aerobic methane-oxidizing bacteria (Bessette et al, 2017). The degradation products of diploptene, hop-21-ene and neoho-13(18)-ene also displayed their highest concentrations at the levee of site C (Figures 4 and 11).…”

“…Both are the only hydrocarbons covarying with the bulk terrestrial indicator G 13 C (Table S2, Supplementary material), which shows that their spatial variability is related to the dominant fraction of terrestrial organic carbon. Both marine and terrestrial lineages of aerobic methane-oxidizing bacteria were characterized in the studied sediments (Bessette et al, 2017) and diploptene and gammacerene variations may reflect alive bacteria associated to soil and river organic matter.…”

Multispecies Populations of Methanotrophic Methyloprofundus and Cultivation of a Likely Dominant Species from the Iheya North Deep-Sea Hydrothermal Field

“…However, the majority of these species are still unidentified. The relative abundance of MOB is often low in environmental microbial communities, and pmoA , the gene encoding particulate methane monooxygenase (pMMO) subunit A, is frequently used as a gene marker for the detection of MOB ( 19 – 23 ). A recent comprehensive classification using large data sets of environmental pmoA sequences revealed habitat preferences among some pmoA clades ( 24 ).…”

Variation of salinity and nitrogen concentration affects the pentacyclic triterpenoid inventory of the haloalkaliphilic aerobic methanotrophic bacterium Methylotuvimicrobium alcaliphilum

“…Aerobic methanotrophs occur in terrestrial, freshwater, and marine ecosystems, preferably at oxic-anoxic interfaces. Aerobic methanotrophic bacteria are microaerophilic, using oxygen as electron acceptor and methane as carbon and energy source (Boetius and Wenzhöfer 2013 ; Bessette et al 2017 ). Generally, aerobic methanotrophs are divided into two major groups, belonging to the Gammaproteobacteria (Type I and Type X methanotrophs) and Alphaproteobacteria (Type II methanotrophs), which differ in physiology, chemotaxonomy, internal ultrastructure, carbon assimilation pathways, and other biochemical aspects (Bowman 2006 ).…”