Degradation of tarballs using associated bacterial consortia.

Tarballs are semi-solid blobs of crude-oil formed in marine environment. Microbial degradation of tarballs is poorly understood, though there are indications that tarball-associated microbes can degrade recalcitrant hydrocarbons present in tarballs. In this study, 38 tarball-associated bacteria from Betul beach, Goa, India were initially screened for crude oil degradation. Based on preliminary studies and literature survey, four bacterial strains, Alcanivorax sp. Betul-O, Marinobacter sp. Betul-26, Pseudomonas sp. Betul-14, and Pseudomonas sp. Betul-M were selected for bacterial consortia preparation. Eleven bacterial consortia were prepared and studied for degradation of n-alkanes and polycyclic aromatic hydrocarbon compounds (PAHs) of tarballs based on gravimetric and GC-MS-MS analyses. The bacterial consortia depleted 53.69-97.78% and 22.78-61.98% of n-alkanes and PAH compounds, respectively, within 45 days. Bacterial consortium comprising Pseudomonas sp. Betul-14, Pseudomonas sp. Betul-M, and Alcanivorax sp. Betul-O exhibited promising tarball degradation abilities with 97.78% and 61.98% degradation of n-alkanes and PAH, respectively, within 45 days. Further research is required to obtain insights into degradation products and possible pathways involved.

Phylogenetic characterization of culturable bacteria and fungi associated with tarballs from Betul beach, Goa, India.

Tarballs are semisolid blobs of crude oil, normally formed due to weathering of crude-oil in the sea after any kind of oil spills. Microorganisms are believed to thrive on hydrocarbon-rich tarballs and possibly assist in biodegradation. The taxonomy of ecologically and economically important tarball-associated microbes, however, needs improvement as DNA-based identification and phylogenetic characterization have been scarcely incorporated into it. In this study, bacteria and fungi associated with tarballs from touristic Betul beach in Goa, India were isolated, followed by phylogenetic analyses of 16S rRNA gene and the ITS sequence-data to decipher their clustering patterns with closely-related taxa. The gene-sequence analyses identified phylogenetically diverse 20 bacterial genera belonging to the phyla Proteobacteria (14), Actinobacteria (3), Firmicutes (2) and Bacteroidetes (1), and 8 fungal genera belonging to the classes Eurotiomycetes (6), Sordariomycetes (1) and Leotiomycetes (1) associated with the Betul tarball samples. Future studies employing a polyphasic approach, including multigene sequence-data, are needed for species-level identification of culturable tarball-associated microbes. This paper also discusses potentials of tarball-associated microbes to degrade hydrocarbons.

Diversity of bacteria and fungi associated with tarballs: Recent developments and future prospects.

Tarballs are formed by weathering of crude oil in marine environment. They are transported from open ocean to the shores by sea currents and waves. Tarball pollution is a major concern to global marine ecosystem. Microbes such as bacteria and fungi are known to be associated with tarballs. They presumably play an important role in tarball degradation and some are potential human and animal pathogens. This paper highlights the recent studies on tarball-associated bacteria and fungi. Future perspectives on diversity, ecology and possible applications of tarball-associated microbes in bioremediation of beached tarballs have been discussed.

The ITS-based phylogeny of fungi associated with tarballs.

Tarballs, the remnants of crude oil which change into semi-solid phase due to various weathering processes in the sea, are rich in hydrocarbons, including toxic and almost non-degradable hydrocarbons. Certain microorganisms such as fungi are known to utilize hydrocarbons present in tarballs as sole source of carbon for nutrition. Previous studies have reported 53 fungal taxa associated with tarballs. There is apparently no gene sequence-data available for the published taxa so as to verify the fungal identification using modern taxonomic tools. The objective of the present study is to isolate fungi from tarballs collected from Candolim beach in Goa, India and investigate their phylogenetic diversity based on 5.8S rRNA gene and the flanking internal transcribed spacer regions (ITS) sequence analysis. In the ITS-based NJ tree, eight tarball-associated fungal isolates clustered with 3 clades of Dothideomycetes and 2 clades of Saccharomycetes. To the best of our knowledge, this is the first study that has employed ITS-based phylogeny to characterize the fungal diversity associated with tarballs. Further studies are warranted to investigate the role of the tarball-associated fungi in degradation of recalcitrant hydrocarbons present in tarballs and the role of tarballs as carriers of human pathogenic fungi.