Biodegradation of polycyclic aromatic hydrocarbons by a halophilic microbial consortium

Abstract

In this study we investigated the phenanthrene degradation by a halophilic consortium obtained from a saline soil sample. This consortium, named Qphe, could efficiently utilize phenanthrene in a wide range of NaCl concentrations, from 1% to 17% (w/v). Since none of the purified isolates could degrade phenanthrene, serial dilutions were performed and resulted in a simple polycyclic aromatic hydrocarbon (PAH)-degrading culture named Qphe-SubIV which was shown to contain one culturable Halomonas strain and one unculturable strain belonging to the genus Marinobacter. Qphe-SubIV was shown to grow on phenanthrene at salinities as high as 15% NaCl (w/v) and similarly to Qphe, at the optimal NaCl concentration of 5% (w/v), could degrade more than 90% of the amended phenanthrene in 6 days. The comparison of the substrate range of the two consortiums showed that the simplified culture had lost the ability to degrade chrysene but still could grow on other polyaromatic substrates utilized by Qphe. Metabolite analysis by HPLC and GC-MS showed that 2-hydroxy 1-naphthoic acid and 2-naphthol were among the major metabolites accumulated in the Qphe-SubIV culture media, indicating that an initial dioxygenation step might proceed at C1 and C2 positions. By investigating the growth ability on various substrates along with the detection of catechol dioxygenase gene, it was postulated that the uncultured Marinobacter strain had the central role in phenanthrene degradation and the Halomonas strain played an auxiliary role in the culture by utilizing phenanthrene metabolites whose accumulation in the media could be toxic.

Bacterial Community Response to Petroleum Hydrocarbon Amendments in Freshwater, Marine, and Hypersaline Water-Containing Microcosms

“…Marinobacter should have a role in PAH degradation in high salinity. Bacteria belonging to the Marinobacter genus degrade both aliphatic and aromatic fractions of petroleum hydrocarbons (47) and have been found to be part of a PAH-degrading halophilic microbial consortium in saline soil (18). Considering alkane-and crude oil-contaminated microcosms, a predominance of Acinetobacter in freshwater microcosms and of Oceanospirillales and Marinobacter in marine and hypersaline microcosms was observed.…”

“…Bacterial hydrocarbon degradation in hypersaline environments has been considered a difficult process because the solubility of hydrocarbons and oxygen is reduced when salinity increases (14). To date, members of the Oceanospirillales order and Marinobacter and Martelella genera (14)(15)(16)(17)(18) have been detected in petroleum hydrocarboncontaminated hypersaline waters. Hydrocarbon-degrading bacteria have already been identified in freshwater (19), but the precise functions of bacterial strains in this environment remain unknown.…”

Aerobic Degradation of Fluoranthene, Benzo(b)Fluoranthene and Benzo(k) Fluoranthene by Aerobic Heterotrophic Bacteria- Cyanobacteria Interaction in Brackish Water of Bodo Creek

“…Two Marinobacters, M. sedimentalis and M. falvimaris were isolated from hypersaline sabkhas due to their capability to grow on crude oil and were observed to have utilized Tween 80 and other individual aliphatic hydrocarbons ranging from C 9 -C 40 as carbon sources in the presence of 6% NaCl [22]. Dastgheib et al [23] [24]. Benzo(k)fluoranthene as a member of the five-ring HMW PAH class was observed to resist biotransformation due to its molecular stability, hydrophobic nature and low water solubility, which is approximately 1 ug L −1 or less [25][26][27].…”

Proteogenomic Elucidation of the Initial Steps in the Benzene Degradation Pathway of a Novel Halophile, Arhodomonas sp. Strain Rozel, Isolated from a Hypersaline Environment

“…and Marinobacter sp. Metabolite analysis using high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) showed that 2-hydroxy-1-naphthoic acid and 2-naphthol were among the major metabolites accumulated in the culture media, indicating that the initial dioxygenation might have occurred by a novel mechanism at the C1 and C2 positions (9).…”

“…These genes were flanked downstream by the benzoate catabolic genes benA and benB, which code for the large and small subunits of benzoate 1,2-dioxygenase, respectively. Recently, Dastgheib et al (9) obtained a phenanthrene-degrading mixed culture (Qphe-SubIV) consisting of two organisms, Halomonas sp. and Marinobacter sp.…”