Reconstruction and evaluation of oil-degrading consortia isolated from sediments of hydrothermal vents in the South Mid-Atlantic Ridge

Abstract

In this study, sediments were collected from two different sites in the deep-sea hydrothermal region of the South Atlantic Ocean. Two microbial enrichment cultures (H7S and H11S), which were enriched from the sediments collected at two sample sites, could effectively degrade petroleum hydrocarbons. The bacterial diversity was analyzed by high-throughput sequencing method. The petroleum degradation ability were evaluated by gas chromatography-mass spectrometry and gravimetric analysis. We found that the dominant oil-degrading bacteria of enrichment cultures from the deep-sea hydrothermal area belonged to the genera Pseudomonas, Nitratireductor, Acinetobacter, and Brevundimonas. After a 14-day degradation experiment, the enrichment culture H11S, which was obtained near a hydrothermal vent, exhibited a higher degradation efficiency for alkanes (95%) and polycyclic aromatic hydrocarbons (88%) than the enrichment culture H7S. Interestingly, pristane and phytane as biomarkers were degraded up to 90% and 91% respectively by the enrichment culture H11S, and six culturable oil-degrading bacterial strains were isolated. Acinetobacter junii strain H11S-25, Nitratireductor sp. strain H11S-31 and Pseudomonas sp. strain H11S-28 were used at a density ratio of 95:4:1 to construct high-efficiency oil-degrading consortium H. After a three-day biodegradation experiment, consortium H showed high degradation efficiencies of 74.2% and 65.7% for total alkanes and PAHs, respectively. The degradation efficiency of biomarkers such as pristane and high-molecular-weight polycyclic aromatic hydrocarbons (such as CHR) reached 84.5% and 80.48%, respectively. The findings of this study indicate that the microorganisms in the deep-sea hydrothermal area are potential resources for degrading petroleum hydrocarbons. Consortium H, which was artificially constructed, showed a highly efficient oil-degrading capacity and has significant application prospects in oil pollution bioremediation.

Figure 1

The oil degradation efficiency of the two enrichment cultures H7S and H11S.

Figure 2

The total n-alkane and PAHs degradation efficiency of two enrichment cultures H7S and H11S (a) n-alkane degradation efficiency, (b) PAHs degradation efficiency.

Figure 3

The n-alkanes and PAHs residual concentration of the crude oil after biodegradation by two enrichment cultures (a) n-Cm: alkane with m carbon atom, for instance, n-C16 is alkane with 16 carbon atom; "PR" is pristane, "PH" is phytane. (b) The concentrations of PAHs after the biodegradation by the 5 strains (NAP, FLU, DBT, PHE, and CHR represent for naphthalene, fluorine, dibenzothiophene, phenanthrene, chrysene, respectively. C1(C2, C3, C4)-NAP, alkylated naphthalene with straight-chain of 1 ~ 4 carbon atoms; C1(C2, C3)-FLU, alkylated fluorene with straight-chain of 1 ~ 3 carbon atoms; C1(C2, C3)-DBT, alkylated dibenantherene with straight-chain of 1 ~ 3 carbon atoms; C1(C2, C3, C4)-PHE, alkylated phenanthrene with straight-chain of 1 ~ 4 carbon atoms; C1(C2)-CHR, alkylated chrysene with straight-chain of 1 ~ 2 carbon atoms).

Figure 4

Bacterial community structure at different levels (a phylum level. b class level. c genus level).

Figure 5

Phylogenetic tree of the oil-degrading strains isolated from the deep-sea sediment samples based on 16S rRNA gene sequences.

Figure 6

The n-alkanes and PAHs residual concentration in the crude oil after biodegrading 21 days by isolated strains and consortia (a n-Cm: alkane with m carbon atom, for instance, n-C16 is alkane with 16 carbon atom; "PR" is pristane, "PH" is phytane. b NAP, FLU, DBT, PHE, and CHR represent for naphthalene, fluorine, dibenzothiophene, phenanthrene, chrysene, respectively. C1(C2, C3, C4)-NAP, alkylated naphthalene with straight-chain of 1 ~ 4 carbon atoms; C1(C2, C3)-FLU, alkylated fluorene with straight-chain of 1 ~ 3 carbon atoms; C1(C2, C3)-DBT, alkylated dibenantherene with straight-chain of 1 ~ 3 carbon atoms; C1(C2, C3, C4)-PHE, alkylated phenanthrene with straight-chain of 1 ~ 4 carbon atoms; C1(C2)-CHR, alkylated chrysene with straight-chain of 1 ~ 2 carbon atoms).