Enzymatic conversion of ε-hexachlorocyclohexane and a heptachlorocyclohexane isomer, two neglected components of technical hexachlorocyclohexane.

α-, ß, γ-, and δ-Hexachlorocyclohexane (HCH), the four major isomers of technical HCH, are susceptible to biotic transformations, whereby only α- and γ-HCH undergo complete mineralization. Nevertheless, LinA and LinB catalyzing HCl elimination and hydrolytic dehalogenations, respectively, as initial steps in the mineralization also convert ß- and δ-HCH to a variety of mainly hydroxylated metabolites. In this study, we describe the isolation of two minor components of technical HCH, ε-HCH, and heptachlorocyclohexane (HeCH), and we present data on enzymatic transformations of both compounds by two dehydrochlorinases (LinA1 and LinA2) and a haloalkane dehalogenase (LinB) from Sphingobium indicum B90A. In contrast to reactions with α-, γ-, and δ-HCH, both LinA enzymes converted ε-HCH to a mixture of 1,2,4-, 1,2,3-, and 1,3,5-trichlorobenzenes without the accumulation of pentachlorocyclohexene as intermediate. Furthermore, both LinA enzymes were able to convert HeCH to a mixture of 1,2,3,4- and 1,2,3,5-tetrachlorobenzene. LinB hydroxylated ε-HCH to pentachlorocyclohexanol and tetrachlorocyclohexane-1,4-diol, whereas hexachlorocyclohexanol was the sole product when HeCH was incubated with LinB. The data clearly indicate that various metabolites are formed from minor components of technical HCH mixtures. Such metabolites will contribute to the overall toxic potential of HCH contaminations and may constitute serious, yet unknown environmental risks and must not be neglected in proper risk assessments.

Pseudomonas sp. to Sphingobium indicum: a journey of microbial degradation and bioremediation of Hexachlorocyclohexane.

The unusual process of production of hexachlorocyclohexane (HCH) and extensive use of technical HCH and lindane has created a very serious problem of HCH contamination. While the use of technical HCH and lindane has been banned all over the world, India still continues producing lindane. Bacteria, especially Sphingomonads have been isolated that can degrade HCH isomers. Among all the bacterial strains isolated so far, Sphingobium indicum B90A that was isolated from HCH treated rhizosphere soil appears to have a better potential for HCH degradation. This conclusion is based on studies on the organization of lin genes and degradation ability of B90A. This strain perhaps can be used for HCH decontamination through bioaugmentation.

Role of electrostatic interactions in the toxicity of titanium dioxide nanoparticles toward Escherichia coli.

The increasing production and use of titanium dioxide nanoparticles (NP-TiO(2)) has led to concerns about their possible impact on the environment. Bacteria play crucial roles in ecosystem processes and may be subject to the toxicity of these nanoparticles. In this study, we showed that at low ionic strength, the cell viability of Escherichia coli was more severely affected at pH 5.5 than at pH 7.0 and pH 9.5. At pH 5.5, nanoparticles (positively charged) strongly interacted with the bacterial cells (negatively charged) and accumulated on their surfaces. This phenomenon was observed in a much lower degree at pH 7.0 (NP-TiO(2) neutrally charged and cells negatively charged) and pH 9.5 (both NP-TiO(2) and cells negatively charged). It was also shown that the addition of electrolytes (NaCl, CaCl(2), Na(2)SO(4)) resulted in a gradual reduction of the NP-TiO(2) toxicity at pH 5.5 and an increase in this toxicity at pH 9.5, which was closely related to the reduction of the NP-TiO(2) and bacterial cell electrostatic charges.

Evaluation of hexachlorocyclohexane contamination from the last lindane production plant operating in India.

PURPOSE: α-Hexachlorocyclohexane (HCH), ß-HCH, and lindane (γ-HCH) were listed as persistent organic pollutants by the Stockholm Convention in 2009 and hence must be phased out and their wastes/stockpiles eliminated. At the last operating lindane manufacturing unit, we conducted a preliminary evaluation of HCH contamination levels in soil and water samples collected around the production area and the vicinity of a major dumpsite to inform the design of processes for an appropriate implementation of the Convention. METHODS: Soil and water samples on and around the production site and a major waste dumpsite were measured for HCH levels. RESULTS: All soil samples taken at the lindane production facility and dumpsite and in their vicinity were contaminated with an isomer pattern characteristic of HCH production waste. At the dumpsite surface samples contained up to 450 g kg(-1) Σ HCH suggesting that the waste HCH isomers were simply dumped at this location. Ground water in the vicinity and river water was found to be contaminated with 0.2 to 0.4 mg l(-1) of HCH waste isomers. The total quantity of deposited HCH wastes from the lindane production unit was estimated at between 36,000 and 54,000 t. CONCLUSIONS: The contamination levels in ground and river water suggest significant run-off from the dumped HCH wastes and contamination of drinking water resources. The extent of dumping urgently needs to be assessed regarding the risks to human and ecosystem health. A plan for securing the waste isomers needs to be developed and implemented together with a plan for their final elimination. As part of the assessment, any polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) generated during HCH recycling operations need to be monitored.

Sphingobium chinhatense sp. nov., a hexachlorocyclohexane (HCH)-degrading bacterium isolated from an HCH dumpsite.

A yellow-pigmented, hexachlorocyclohexane (HCH)-degrading bacterium, strain IP26(T), was isolated from an HCH dumpsite and subjected to a polyphasic analysis in order to determine its taxonomic position. Strain IP26(T) showed maximum 16S rRNA gene sequence similarity with Sphingobium francense Sp+(T) (98.5 %), Sphingobium japonicum UT26(T) (98.4 %) and Sphingobium indicum B90A(T) (98.2 %). Phylogenetic analysis based on 16S rRNA gene sequences also showed that strain IP26(T) formed a cluster with these three HCH-degrading strains. Chemotaxonomic data (major polyamine, spermidine; major quinone, ubiquinone with ten isoprene units; major polar lipids, phosphatidylmonomethylethanolamine, phosphatidylethanolamine, diphosphatidylglycerol, phosphotidylcholine; and presence of 2-hydroxy fatty acid) supported inclusion of strain IP26(T) in the genus Sphingobium. However, the results of DNA-DNA hybridization and morphological and biochemical tests clearly allowed phenotypic and genotypic differentiation of strain IP26(T) from recognized species of the genus Sphingobium. Strain IP26(T) thus represents a novel species of the genus Sphingobium for which the name Sphingobium chinhatense sp. nov. is proposed. The type strain is IP26(T) (=MTCC8598(T) =CCM 7432(T)).

Devosia albogilva sp. nov. and Devosia crocina sp. nov., isolated from a hexachlorocyclohexane dump site.

Two bacterial strains, IPL15(T) and IPL20(T), isolated from a hexachlorocyclohexane dump site in India, were characterized by using a polyphasic approach. Based on 16S rRNA gene sequence analysis, both strains belonged to the genus Devosia; highest sequence similarities of strain IPL15(T) were observed with Devosia neptuniae J1(T) and Devosia geojensis BD-c194(T) (96.2 % in each case) and the highest sequence similarity of strain IPL20(T) was observed with Devosia soli GH2-10(T) (98.6 %). Phylogenetic analysis showed the distinct lineages of strains IPL15(T) and IPL20(T) among members of the genus Devosia. The presence of C(18 : 0) 3-OH and C(10 : 0) 3-OH fatty acids supported their respective positions within the genus Devosia. On the basis of phenotypic characteristics, phylogenetic analysis and DNA-DNA hybridization results, it is concluded that strains IPL15(T) and IPL20(T) represent two distinct species of the genus Devosia for which the names Devosia albogilva sp. nov. and Devosia crocina sp. nov., respectively, are proposed. The type strains are Devosia albogilva IPL15(T) (=CCM 7427(T)=MTCC 8594(T)) and Devosia crocina IPL20(T) (=CCM 7425(T)=MTCC 8590(T)).

Flavobacterium lindanitolerans sp. nov., isolated from hexachlorocyclohexane-contaminated soil.

A Gram-negative, non-spore-forming, cream-yellow-pigmented bacterial strain, IP-10(T), was isolated from soil samples from a waste site highly contaminated with hexachlorocyclohexane in Ummari village, India. The organism showed the highest 16S rRNA gene sequence similarity of 92.7 % with Flavobacterium soli KCTC 12542(T) and levels of 87-92 % with the type strains of other recognized species of the genus Flavobacterium. The DNA G+C content of strain IP-10(T) was 31 mol%. The predominant fatty acids were iso-C(15 : 0) (22.1 %), iso-C(17 : 0) 3-OH (18.5 %) and summed feature 3 (comprising C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH; 13.2 %). Strain IP-10(T) could be differentiated from recognized species of the genus Flavobacterium based on a number of phenotypic features. Strain IP-10(T) is therefore considered to represent a novel species of the genus Flavobacterium, for which the name Flavobacterium lindanitolerans sp. nov. is proposed. The type strain is IP-10(T) (=MTCC 8597(T)=CCM 7424(T)).

Enhanced biodegradation of hexachlorocyclohexane (HCH) in contaminated soils via inoculation with Sphingobium indicum B90A.

Soil pollution with hexachlorocyclohexane (HCH) has caused serious environmental problems. Here we describe the targeted degradation of all HCH isomers by applying the aerobic bacterium Sphingobium indicum B90A. In particular, we examined possibilities for large-scale cultivation of strain B90A, tested immobilization, storage and inoculation procedures, and determined the survival and HCH-degradation activity of inoculated cells in soil. Optimal growth of strain B90A was achieved in glucose-containing mineral medium and up to 65% culturability could be maintained after 60 days storage at 30 degrees C by mixing cells with sterile dry corncob powder. B90A biomass produced in water supplemented with sugarcane molasses and immobilized on corncob powder retained 15-20% culturability after 30 days storage at 30 degrees C, whereas full culturability was maintained when cells were stored frozen at -20 degrees C. On the contrary, cells stored on corncob degraded gamma-HCH faster than those that had been stored frozen, with between 15 and 85% of gamma-HCH disappearance in microcosms within 20 h at 30 degrees C. Soil microcosm tests at 25 degrees C confirmed complete mineralization of [(14)C]-gamma-HCH by corncob-immobilized strain B90A. Experiments conducted in small pits and at an HCH-contaminated agricultural site resulted in between 85 and 95% HCH degradation by strain B90A applied via corncob, depending on the type of HCH isomer and even at residual HCH concentrations. Up to 20% of the inoculated B90A cells survived under field conditions after 8 days and could be traced among other soil microorganisms by a combination of natural antibiotic resistance properties, unique pigmentation and PCR amplification of the linA genes. Neither the addition of corncob nor of corncob immobilized B90A did measurably change the microbial community structure as determined by T-RFLP analysis. Overall, these results indicate that on-site aerobic bioremediation of HCH exploiting the biodegradation activity of S. indicum B90A cells stored on corncob powder is a promising technology.

Hexachlorocyclohexane-degrading bacterial strains Sphingomonas paucimobilis B90A, UT26 and Sp+, having similar lin genes, represent three distinct species, Sphingobium indicum sp. nov., Sphingobium japonicum sp. nov. and Sphingobium francense sp. nov., and reclassification of [Sphingomonas] chungbukensis as Sphingobium chungbukense comb. nov.

Three strains of Sphingomonas paucimobilis, B90A, UT26 and Sp+, isolated from different geographical locations, were found to degrade hexachlorocyclohexane. Phylogenetic analysis based on 16S rRNA gene sequences indicated that these strains do not fall in a clade that includes the type strain, Sphingomonas paucimobilis ATCC 29837(T), but form a coherent cluster with [Sphingomonas] chungbukensis IMSNU 11152(T) followed by Sphingobium chlorophenolicum ATCC 33790(T). The three strains showed low DNA-DNA relatedness values with Sphingomonas paucimobilis ATCC 29837(T) (8-25%), [Sphingomonas] chungbukensis IMSNU 11152(T) (10-17%), Sphingobium chlorophenolicum ATCC 33790(T) (23-54%) and Sphingomonas xenophaga DSM 6383(T) (10-28%), indicating that they do not belong to any of these species. Although the three strains were found to be closely related to each other based on 16S rRNA gene sequence similarity (99.1-99.4%), DNA-DNA relatedness (19-59%) and pulsed-field gel electrophoresis (PFGE) patterns indicated that they possibly represent three novel species of the genus Sphingobium. The three strains could also be readily distinguished by biochemical tests. The three strains showed similar polar lipid profiles and contained sphingoglycolipids. The strains differed from each other in fatty acid composition but contained the predominant fatty acids characteristic of other Sphingobium species. A phylogenetic study based on 16S rRNA gene sequences showed that [Sphingomonas] chungbukensis IMSNU 11152(T) formed a cluster with members of the genus Sphingobium. Based on these results, it is proposed that strains B90A, UT26 and Sp+, previously known as Sphingomonas paucimobilis, are the type strains of Sphingobium indicum sp. nov. (=MTCC 6364(T)=CCM 7286(T)), Sphingobium japonicum sp. nov. (=MTCC 6362(T)=CCM 7287(T)) and Sphingobium francense sp. nov. (=MTCC 6363(T)=CCM 7288(T)), respectively. It is also proposed that [Sphingomonas] chungbukensis be transferred to Sphingobium chungbukense comb. nov.