Anaerobic oxidation of petroleum hydrocarbons in enrichment cultures from sediments of the Gorevoy Utes natural oil seep under methanogenic and sulfate-reducing conditions.

O N Pavlova,A G Gorshkov,T I Zemskaya,S M Chernitsyna,T V Pogodaeva,A V Khabuev,V G Ivanov,O N Izosimova

doi:10.1007/s00248-021-01802-y

O N Pavlova, A G Gorshkov + Show 6 more

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This article presents the first experimental data on the ability of microbial communities from sediments of the Gorevoy Utes natural oil seep to degrade petroleum hydrocarbons under anaerobic conditions. Like in marine ecosystems associated with oil discharge, available electron acceptors, in particular sulfate ions, affect the composition of the microbial community and the degree of hydrocarbon conversion. The cultivation of the surface sediments under sulfate-reducing conditions led to the formation of a more diverse bacterial community and greater loss of n-alkanes (28%) in comparison to methanogenic conditions (6%). Microbial communities of both surface and deep sediments are more oriented to degrade polycyclic aromatic hydrocarbons (PAHs), to which the degree of the PAH conversion testifies (up to 46%) irrespective of the present electron acceptors. Microorganisms with the uncultured closest homologues from thermal habitats, sediments of mud volcanoes, and environments contaminated with hydrocarbons mainly represented microbial communities of enrichment cultures. The members of the phyla Firmicutes, Chloroflexi, and Caldiserica (OP5), as well as the class Deltaproteobacteria and Methanomicrobia, were mostly found in enrichment cultures. The influence of gas-saturated fluids may be responsible for the presence in the bacterial 16S rRNA gene libraries of the sequences of "rare taxa": Planctomycetes, Ca. Atribacteria (OP9), Ca. Armatimonadetes (OP10), Ca. Latescibacteria (WS3), Ca. division (AC1), Ca. division (OP11), and Ca. Parcubacteria (OD1), which can be involved in hydrocarbon oxidation.

Highlights

Deep petroleum reservoirs and deep sediments associated with oil discharge have long been considered biotopes unsuitable for life [1]
In subsurface and deep sediments of the Gorevoy Utes natural oil seep, under methanogenic and sulfatereducing conditions, we recorded the loss of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) accompanied by the methane formation
In the enrichment cultures containing surface sediments, the n-alkane conversion was the most intense in the presence of sulfate ions, and in those containing deep ones – of bicarbonate ions, which can be due to the composition of microbial communities developing under various conditions

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Introduction

Deep petroleum reservoirs and deep sediments associated with oil discharge have long been considered biotopes unsuitable for life [1]. The use of a set of methods has described microbial diversity in petroleum reservoirs, revealed dominant groups of microorganisms that carry out anaerobic oxidation of oil, determined metabolic pathways and the resulting oxidation products [2,3,4,5,6,7,8,9,10,11]. The study of the strategy of energy and carbon adsorption by microbial communities from three deep oil seepages (water column depth 3 km) in the eastern part of the Gulf of Mexico using metagenomic, geochemical and metabolomic analyses revealed that deep sediments contain phylogenetically and functionally diverse microbial communities that carry out anaerobic metabolism of hydrocarbons where acetate and hydrogen are the central intermediates underpinning community interactions and biogeochemical cycling in these deep sediments. Bathyarchaeota, whose genomes contain genes of anaerobic oxidation of hydrocarbons through hydroxylation and addition of hydrocarbons to fumarate as well as of degradation of anaerobic aromatic compounds through class I benzoyl-CoA reductase [12]

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