Candidatus Alkanophaga archaea from Guaymas Basin hydrothermal vent sediment oxidize petroleum alkanes

Oil-rich deep-sea sediments are used to culture syntrophic communities of archaea and bacteria that pair petroleum alkane oxidation to sulfide generation. Methanogenic and methanotrophic archaea produce and consume the greenhouse gas methane, respectively, using the reversible enzyme methyl-coenzyme M reductase (Mcr). Recently, Mcr variants that can activate multicarbon alkanes have been recovered from archaeal enrichment cultures. These enzymes, called alkyl-coenzyme M reductase (Acrs), are widespread in the environment but remain poorly understood. Here we produced anoxic cultures degrading mid-chain petroleum n-alkanes between pentane (C-5) and tetradecane (C-14) at 70 degrees C using oil-rich Guaymas Basin sediments. In these cultures, archaea of the genus Candidatus Alkanophaga activate the alkanes with Acrs and completely oxidize the alkyl groups to CO2. Ca. Alkanophaga form a deep-branching sister clade to the methanotrophs ANME-1 and are closely related to the short-chain alkane oxidizers Ca. Syntrophoarchaeum. Incapable of sulfate reduction, Ca. Alkanophaga shuttle electrons released from alkane oxidation to the sulfate-reducing Ca. Thermodesulfobacterium syntrophicum. These syntrophic consortia are potential key players in petroleum degradation in heated oil reservoirs.

Automated summary

Oil-rich deep-sea sediments are used to culture syntrophic communities of archaea and bacteria that pair petroleum alkane oxidation to sulfide generation. Recently, enzymes that can activate multicarbon alkanes have been recovered from archaeal enrichment cultures. Anoxic cultures degrading mid-chain petroleum n-alkanes at 70 degrees C using oil-rich Guaymas Basin sediments were produced. These cultures revealed the presence of archaea of the genus Candidatus Alkanophaga that activate the alkanes and oxidize alkyl groups to CO2.