Variability in Genomic Patterns of Bacterial Communities Related to Tarmats and Quantification of Hydrocarbon Present in the Tarmats Deposited along the Qatar Coast

Abstract

Qatar has undergone a rapid transition from a fishing and small agriculture to an economy focused on oil and gas since 1960. Owing to the comparatively large level of oil and gas production, the region has become severely contaminated by oil pollution including tar residues on the coast. Such chemical and biologically transformed oil residues are particularly important because they are expected to degrade gradually. In the present study, tarmat samples collected from 16 locations along the Qatar coast were subject to chemical and metagenomics analyses. The study includes investigation of bacterial community by 16S rRNA based identification of isolates, followed by Illumina sequencing and metagenomic analysis along with determination of TPH and PAH concentrations by GC and ATR-FTIR analyses. GC-MS analyses confirmed the presence of PAHs in tarmat samples, with the highest level of Benzo(g,h,i)perylene, collected from Al Arish (13.893ppb), Abu Samra (11.973ppb) and Ras Laffan (11.530). High molecular weight (HMW) PAHs dominated in the total PAH composition, and low molecular weight (LMW) PAHs such as fluorene and phenanthrene were not detected in any of the studied tarmat samples. ATR-FTIR absorption spectra for tarmat samples showed notable peaks at 2919 cm-1 and 2850 cm-1, confirming the presence of C-H stretch in alkanes. Tarmat samples from west and south coasts of Qatar are characterized with weakly condensed aromatic structures compared to those found in north and east coasts. Northern and western coasts showed a higher quantity of aliphatic composition (1.4509 and 1.1921) compared to the eastern and southern coasts (0.5498 and 0.1706). Microbes associated with tarmats are stated to have toxic degradation capabilities for the hydrocarbons. Hence, diversity of bacterial communities associated with tarmats along Qatar coastline have studied based on V3-V4 regions of 16S rRNA gene sequenced using Illumina Miseq Platform . Phylum Proteobacteria were found dominant in all the tarmat sample studied. Identified abundant genera include Alkalimnicola, Alkanivorax, Marinobacter, Petrotoga, Defluvicoccus and KCM-B112. Marinobacter and Alkanivorax are the major hydrocarbon degraders from the observed bacterial communities. Estimation of diversity indices have proved northern coasts are higher in bacterial diversity. This is the first metagenomic study of tarmat associated bacterial community in Qatar.