Microaerobic conditions caused the overwhelming dominance of Acinetobacter spp. and the marginalization of Rhodococcus spp. in diesel fuel/crude oil mixture-amended enrichment cultures

Abstract

The aim of the present study was to reveal how different microbial communities evolve in diesel fuel/crude oil-contaminated environments under aerobic and microaerobic conditions. To investigate this question, aerobic and microaerobic bacterial enrichments amended with a diesel fuel/crude oil mixture were established and analysed. The representative aerobic enrichment community was dominated by Gammaproteobacteria (64.5%) with high an abundance of Betaproteobacteriales (36.5%), followed by Alphaproteobacteria (8.7%), Actinobacteria (5.6%), and Candidatus Saccharibacteria (4.5%). The most abundant alkane monooxygenase ( alkB ) genotypes in this enrichment could be linked to members of the genus Rhodococcus and to a novel Gammaproteobacterium, for which we generated a high-quality draft genome using genome-resolved metagenomics of the enrichment culture. Contrarily, in the microaerobic enrichment, Gammaproteobacteria (99%) overwhelmingly dominated the microbial community with a high abundance of the genera Acinetobacter (66.3%), Pseudomonas (11%) and Acidovorax (11%). Under microaerobic conditions, the vast majority of alkB gene sequences could be linked to Pseudomonas veronii . Consequently, results shed light on the fact that the excellent aliphatic hydrocarbon degrading Rhodococcus species favour clear aerobic conditions, while oxygen-limited conditions can facilitate the high abundance of Acinetobacter species in aliphatic hydrocarbon-contaminated subsurface environments.

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