First insights into bacterial communities in pre-salt oil reveal a far-from-sterile environment

[Display omitted] •Pre-salt oil presented high bacterial diversity with exclusive uncultured genera.•Pre-salt samples are as rich as oil non-contaminated environments.•Aromatic degradation pathways were significantly enriched in pre-salt samples. The ultra-deep pre-salt oil reservoirs have attracted...

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Bibliographic Details
Published in:Fuel (Guildford) 2022-03, Vol.312, p.122860, Article 122860
Main Authors: da Fonsêca, Marbella Maria Bernardes, Freitas, Júlia Firme, Silva-Portela, Rita de Cássia Barreto, Minnicelli, Carolina Fonseca, da Silva-Barbalho, Kamilla Karla, Agnez-Lima, Lucymara Fassarella
Format: Article
Language:English
Subjects:
16S rRNA gene
Aromatic compounds
Biodegradation
Biodiversity
Biogeochemical cycles
Carbon dioxide
Contamination
Enhanced oil recovery
Gene pool
Genera
High pressure
Microbial activity
Microbial diversity
Microbiome
Microbiomes
Microbiota
Microorganisms
Oil and gas fields
Oil fields
Oil pollution
Oil recovery
Oil reservoir
Oil reservoirs
Petroleum
Pre-salt oil
Reservoirs
Rocks
rRNA 16S
Salts
Taxonomy
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Summary:[Display omitted] •Pre-salt oil presented high bacterial diversity with exclusive uncultured genera.•Pre-salt samples are as rich as oil non-contaminated environments.•Aromatic degradation pathways were significantly enriched in pre-salt samples. The ultra-deep pre-salt oil reservoirs have attracted attention owing to their high oil quality and unique characteristics, such as high pressure and high carbon dioxide content. However, its microbiome has been poorly explored. We conducted 16S rRNA sequencing of two pre-salt oils, three production water, and three rock samples from Brazilian oil reservoirs. Both pre-salt oil samples (respectively, Oil1 from a 6,000-meter-deep and Oil2 from 4,000-meter deep reservoirs) demonstrated higher operational taxonomic unit (OTU) richness when compared to rock and production water. Pre-salt samples showed 60.8% of exclusive genera, among which 122 with no report in the literature concerning oil degradation. Only 11.67% of the pre-salt oil genera was shared with rock and 5.44% with production water groups. Ralstonia and Vogesella dominated the pre-salt oil samples (Oil1 and Oil2) with 39.3% and 37.6%, respectively. To detect taxonomic signatures of different environments and whether the pre-salt oil resembles oil-contaminated biodiversity, we conducted a broad comparison with contaminated, non-contaminated, and oil reservoir samples worldwide. The differences in microbial communities between samples concerning community membership were measured with the Bray-Curtis dissimilarity matrix. Similarity analysis (ANOSIM) showed that microbiomes grouped according to the BioProject, presenting a distinct differentiation (R = 0.95, P ≤ 0.001). The candidate phylum FCPU426 is mainly enriched in pre-salt samples. The functional inference revealed a greater abundance of microorganisms associated with aromatic compounds degradations in pre-salt samples, possibly related to high oil quality in these reservoirs. In conclusion, pre-salt oil exhibited higher biodiversity than other oil field samples. It revealed an unexpected indigenous microbial richness on deep reservoirs not subjected to enhanced oil recovery processes, indicating a microbiota adapted to this inhospitable environment, with a high occurrence of uncultivated or poorly classified taxa, representing a gene pool whose importance for biogeochemical cycles should be further investigated.
ISSN:0016-2361
1873-7153
DOI:10.1016/j.fuel.2021.122860