The nucleotide sequence of Shigella flexneri 1A: A common Indian isolate.

We report complete sequences of 2 genes of S.flexneri 1a an Indian isolate for the first time. Shigella is causative agent of shigellosis or bacillary dysentery. Genomic library was constructed by shotgun approach. Sequencing was carried out using Big Dye terminator chemistry using ABI 3730 48 capillary DNA analyzer. 170 recombinants were subjected to nucleotide sequencing. Sequence data was analyzed, of these 2 clones showed presence of complete genes out of the total clones sequenced. Annotations were done using various bioinformatics tools. Gene Sfo676 on contig SF21B11, 513 bp long codes for a protein 170 aa long with molecular weight of 18836.5 daltons. The protein is 99 % identical to S. flexneri 2a 301 and not with any other strain of Shigella. It has 7 different sites for phosphorylation, myristoylation and glycosylation. Predicted cellular localization is cytoplasmic membrane. SF0368 is another full-length gene SF0368 on contig SF69C1 is a 312 nucleotide long. It is 103 aa long with molecular weight 11394.0 daltons. Protein is 100% identical to S. flexneri 2a 301 and 99% with S. sonnei strain 046. The gene shows difference when compared with S.sonnei in mono and dinucleotide frequency as well as amino acid composition.

Synthesis and spectral properties of DNA capped CdS nanoparticles in aqueous and non-aqueous media.

Synthesis of novel cadmium sulphide nanoparticles has been carried out in aqueous and non-aqueous media. DNA has been added during the synthesis of the nanoparticles, which results into cadmium-rich nanoparticles forming a stable complex with DNA. These particles exhibit strong fluorescence, spectral nature of which depends upon the medium in which the particles are synthesized. When interacted with proteins, fluorescence peak intensity of CdS nanoparticles increases considerably. It is possible that such CdS nanoparticles would be useful as a protein sensor.

2,4,6-trinitrotoluene transformation by a tropical marine yeast, Yarrowia lipolytica NCIM 3589.

Yarrowia lipolytica NCIM 3589, a tropical marine degrader of hydrocarbons and triglycerides transformed 2,4,6-trinitrotoluene (TNT) very efficiently. Though this yeast could not utilize TNT as the sole carbon or nitrogen source, it was capable of reducing the nitro groups in TNT to aminodinitrotoluene (ADNT). In a complete medium containing glucose and ammonium sulphate as the available carbon and nitrogen sources respectively, the culture was able to completely transform 1 mM (227 ppm) of TNT under such conditions. A dual pathway was found to be functional, one of which resulted in the formation of the hydride-Meisenheimer complex (H(-)TNT) as a transiently accumulating metabolite that was subsequently denitrated to 2,4-dinitrotoluene (2,4-DNT), whereas the other pathway resulted in the formation of amino derivatives. The presence of increasing amounts of reducing equivalents in the form of glucose promoted better growth and the nitroreductases of this yeast to reduce the aromatic ring to 2,4-DNT although, the reduction of the nitro groups to amino groups was the major functional pathway. The ability of this tropical marine yeast to transform TNT into products such as 2,4-DNT which in turn could be metabolized by other microbes has implications in the use of this yeast for bioremediation of TNT polluted marine environments.

Cytosine methylation inhibits expression of hsp-CAT gene in Drosophila cells.

Chloramphenicol acetyl transferase gene under control of hsp promoter (hsp-CAT gene) was introduced and expressed upon heat shock in Drosophila cells at 48 and 72 hr following transfection. Expression of CAT gene was remarkably reduced when DNA methylated at CpG sites was used although presence of methylated plasmid DNA could be demonstrated in cells at 48 and 72 hr. Thus, in Drosophila cells exogenously introduced methylated DNA is expressed differently from unmethylated DNA.

Characterization of MboI repeat DNA sequence of Anopheles stephensi.

MboI repeat fragment of mosquito Anopheles stephensi has been isolated by molecular cloning. The restriction map and entire nucleotide sequence of the 433bp insert has been determined. Hybridization of this repeat DNA with restriction enzyme digest of mosquito DNA does not show an interspersed pattern but suggests that this repeat may be tandemly repeated at one major site and a few minor sites in the genome of Anopheles stephensi. The hybridization pattern also indicates that this repeat family comprises of many similar but non-identical sequences. An open reading frame encoding 66 amino acids with an initiation and two tandem termination codons has been identified. This putative 66 amino acid polypeptide sequence has significant homology to a small region of RNA tumour viral envelope protein.

Hemimethylation of DNA prevents chromatin expression.

The activity of hemimethylated herpes simplex virus thymidine kinase DNA and chromatin was analyzed by microinjection and thymidine incorporation into the DNA of thymidine kinase-negative Rat2 cells. Hemimethylated DNA was obtained by in vitro replication of single-stranded M13 DNA constructs and of chromatin produced by in vitro reconstitution of the DNA with purified chicken histone octamers. We found that methylation of either the coding or the noncoding DNA strand was sufficient to block expression of the hemimethylated chromatin. In contrast, the hemimethylated DNA was as active as the unmethylated control DNA after microinjection until chromatin formation occurred in the recipient cells. Microinjection of chromatin hemimethylated by bacterial Hae III methyltransferase excluded the possibility that inactivation was caused by symmetrical methylation of the injected molecules.