Ten halophilic Archaea (Haloarchaea) strains able to degrade aromatic compounds were isolated from five hypersaline locations; salt marshes in the Uyuni salt flats in Bolivia, crystallizer ponds in Chile and Cabo Rojo (Puerto Rico), and sabkhas (salt flats) in the Persian Gulf (Saudi Arabia) and the Dead Sea (Israel and Jordan). Phylogenetic identification of the isolates was determined by 16S rRNA gene sequence analysis. The isolated Haloarchaea strains were able to grow on a mixture of benzoic acid, p-hydroxybenzoic acid, and salicylic acid (1.5mM each) and a mixture of the polycyclic aromatic hydrocarbons, naphthalene, anthracene, phenanthrene, pyrene and benzo[a]anthracene (0.3mM each). Evaluation of the extent of degradation of the mixed aromatic hydrocarbons demonstrated that the isolates could degrade these compounds in hypersaline media containing 20% NaCl. The strains were shown to reduce the COD of hypersaline crude oil reservoir produced waters significantly beyond that achieved using standard hydrogen peroxide treatment alone.

Phenol is a toxic aromatic compound used or produced in many industries and as a result a common component of industrial wastewaters. Phenol containing waste streams are frequently hypersaline and therefore require halophilic microorganisms for efficient biotreatment without dilution. In this study three halophilic bacteria isolated from different saline environments and identified as Halomonas organivorans, Arhodomonas aquaeolei and Modicisalibacter tunisiensis were shown to be able to grow on phenol in hypersaline media containing 100 g/L of total salts at a concentration of 3 mM (280 mg/L), well above the concentration found in most waste streams. Genes encoding the aromatic dioxygenase enzymes catechol 1,2 dioxygenase and protocatechuate 3,4-dioxygenase were present in all strains as determined by PCR amplification using primers specific for highly conserved regions of the genes. The gene for protocatechuate 3,4-dioxygenase was cloned from the isolated H. organivorans and the translated protein was evaluated by comparative protein sequence analysis with protocatechuate 3,4-dioxygenase proteins from other microorganisms. Although the analysis revealed a wide range of sequence divergence among the protocatechuate 3,4-dioxygenase family, all of the conserved domain amino acid structures identified for this enzyme family are identical or conservatively substituted in the H. organivorans enzyme.

Aims To isolate and characterize the cultivable community of hydrolase producers (amylase, protease, lipase, DNase, xylanase and pullulanase) inhabiting heavy‐metal‐contaminated soils in extreme conditions from the Atacama Desert. Methods and Results A total of 25 bacterial strains showing hydrolytic activities have been selected including halotolerants, extremely halotolerants and moderate halophiles. Most hydrolase producers were assigned to the family B acillaceae, belonging to the genera Bacillus (nine strains), Halobacillus (seven strains) and Thalassobacillus (five strains) and four isolates were related to members of the families Pseudomonadaceae, Halomonadaceae and Staphylococcaceae. The selected strains were then characterized for their tolerance pattern to six heavy metals, measured as minimal inhibitory concentrations (MICs). Conclusions The diversity found in the cultivable bacterial community analysed is more limited than that detected in other ecological studies owing to the restrictive conditions used in the screening. The dominant bacteria were Firmicutes and particularly, species related to the genus Bacillus. Significance and Impact of the Study This study is focused on the characterization of extremophilic hydrolytic bacteria, providing candidates as a source of novel enzymes with biotechnological applications.

BACKGROUND: Fipronil is a broad-spectrum insecticide that is used extensively due to its effective action in pest control. However, environmental studies have shown it has high toxicity towards non-target organisms as well. In addition, the degradation of fipronil can generate even more toxic and reactive metabolites in the environment. In the present study, bioprospecting for bacteria with the potential to degrade fipronil was performed using fipronil as the sole source of nitrogen and main source of carbon. From samples of corn culture soil with a history of fipronil application, isolation was performed using the microcosm enrichment method. RESULTS: Bacteria were isolated using fipronil (0.6 g L −1 ) as the sole nitrogen source and main carbon source. After preliminary tests, isolate E1 was selected and, following sequencing of 16S rRNA, it was found that the isolate E1 was a bacterium of the Bacillaceae family, Bacillus megaterium species. Growth was evaluated by dry biomass and degradation quantified by gas chromatography-mass spectrometry (GC-MS). Strain E1 presented a 94% degradation of fipronil, as well as 91% and 96% degradation of its metabolites fipronil-sulfide and fipronil-sulfone, respectively, in 14 days, reducing its initial concentration from 0.6 g L −1 to 0.036 mg L −1 . CONCLUSION: The results showed that bioprospecting of the E1 strain, isolated from soil, showed efficiency in the biodegradation process of fipronil. This strain is a potential candidate for use in bioremediation processes in areas contaminated with fipronil and for use in further studies on the elucidation of the metabolic pathways of fipronil degradation.

No abstract