SUMMARY Lindane, the γ-isomer of hexachlorocyclohexane (HCH), is a potent insecticide. Purified lindane or unpurified mixtures of this and α-, β-, and δ-isomers of HCH were widely used as commercial insecticides in the last half of the 20th century. Large dumps of unused HCH isomers now constitute a major hazard because of their long residence times in soil and high nontarget toxicities. The major pathway for the aerobic degradation of HCH isomers in soil is the Lin pathway, and variants of this pathway will degrade all four of the HCH isomers although only slowly. Sequence differences in the primary LinA and LinB enzymes in the pathway play a key role in determining their ability to degrade the different isomers. LinA is a dehydrochlorinase, but little is known of its biochemistry. LinB is a hydrolytic dechlorinase that has been heterologously expressed and crystallized, and there is some understanding of the sequence-structure-function relationships underlying its substrate specificity and kinetics, although there are also some significant anomalies. The kinetics of some LinB variants are reported to be slow even for their preferred isomers. It is important to develop a better understanding of the biochemistries of the LinA and LinB variants and to use that knowledge to build better variants, because field trials of some bioremediation strategies based on the Lin pathway have yielded promising results but would not yet achieve economic levels of remediation.

Classification of microorganisms on the basis of fi traditional microbiological methods (morphological, physiological and biochemical) creates a blurred image about their taxonomic status and thus needs further clarification. It fi should be based on a more pragmatic approach of deploying a number of methods for the complete characterization of microbes. Hence, the methods now employed for bacterial systematics include, the complete 16S rRNA gene sequencing and its comparative analysis by phylogenetic trees, DNA-DNA hybridization studies with related organisms, analyses of molecular markers and signature pattern(s), biochemical assays, physiological and morphological tests. Collectively these genotypic, chemotaxonomic and phenotypic methods for determining taxonomic position of microbes constitute what is known as the 'polyphasic approach' for bacterial systematics. This approach is currently the most popular choice for classifying bacteria and several microbes, which were previously placed under invalid taxa have now been resolved into new genera and species. This has been possible owing to rapid development in molecular biological techniques, automation of DNA sequencing coupled with advances in bioinformatic tools and access to sequence databases. Several DNA-based typing methods are known; these provide information for delineating bacteria into different genera and species and have the potential to resolve differences among the strains of a species. Therefore, newly isolated strains must be classifi ed fi on the basis of the polyphasic approach. Also previously classifi ed organisms, as and when required, can be reclasfi sified on this ground in order to obtain information about fi their accurate position in the microbial world. Thus, current techniques enable microbiologists to decipher the natural phylogenetic relationships between microbes.

A phenanthrene-and citronellol-degrading bacterium, strain RLD-1 T , was isolated from the fly ash dumping site of a thermal power plant in Delhi, India. The 16S rRNA gene sequence indicated that this strain belongs to the genus Pseudomonas; high levels of sequence similarity were found with respect to Pseudomonas citronellolis DSM 50332 T (98.9 %), Pseudomonas jinjuensis DSM 16612 T (97.6 %) and Pseudomonas nitroreducens DSM 14399 T (97.5 %). Phylogenetic analysis based on 16S rRNA gene sequences placed the strain within the clade represented by these three strains. Strain RLD-1 T showed low levels of DNA-DNA hybridization with respect to P.citronellolis DSM 50332 T (36 %), P. jinjuensis DSM 16612 T (4 %) and P. nitroreducens (13.7 %).Strain RLD-1 T can also be distinguished from these three strains on the basis of several biochemical and physiological attributes. The novel strain contained high levels of cellular fatty acids 18 : 1v7c, 16 : 0 and 16 : 1v7c, along with 10 : 0 3-OH and 12 : 0 3-OH. Thus, strain RLD-1 T represents a novel species of the genus Pseudomonas, for which the name Pseudomonas delhiensis sp. nov. is proposed. The type strain is RLD-1 T (=MTCC 7601 T =CCM 7361 T ).

The study demonstrates that biostimulation of indigenous HCH-degrading microbial population can be used for decontamination of chronically HCH-contaminated sites.

Amycolatopsis mediterranei S699 is an actinomycete that produces an important antibiotic, rifamycin B. Semisynthetic derivatives of rifamycin B are used for the treatment of tuberculosis, leprosy, and AIDS-related mycobacterial infections. Here, we report the complete genome sequence (10.2 Mb) of A. mediterranei S699, with 9,575 predicted coding sequences.