Abstract:[Background] Understanding functional microbiota inside crude oil samples is crucial in microbiota design for enhancing oil recovery. [Objective] Identifying potential core functional microbiota from a crude oil sample that have ability to produce acid/gas through metagenomic analysis. [Methods] The compositional and functional changes of the indoor activated crude oil samples were obtained with the metagenomic data. The potential endogenous core functional microbiota related to the production of gas and acid were obtained through bioinformatics, multivariate statistics and network analysis. [Results] The co-abundance analysis deduced that Bacillus licheniformis, along with Coprothermobacter proteolyticus, Marinobacter spp., Anaerbaculum hydrogeniforms and Petrotoga mobilis that clustered as a group, were the core functional bacteria relevant to the change of the pH value. Functional analysis of strains in this group through draft genome assembly indicated that the pathways for acid production, including for lactic acid, acetic acid and formic acid fermentation using pyruvate/acetyl coenzyme A, were enriched. Enterococcus faecium was considered as the core microbe in another group, which had Shinella zoogloeoides, Paracoccus deniticans, Paracoccus spp. and Enterobacter cloacae. Among these, Enterobacter cloacae was positively correlated with total gas production. The assembled bins in this group had the ability to produce nitrogen/sulfur/carbon using nitrate (nitrite)/sulfate (sulfite)/petroleum hydrocarbon. These two groups both had a small number of microbes that have dual ability for gas and acid production and the two groups were negatively correlated. [Conclusion] We had screened out core acid/gas producing microbiota in a crude oil sample through organic activation and metagenomic sequencing technology. These findings provided potential strain targets for further research.
