Cloning and DNA sequence of plasmid determinant iss, coding for increased serum survival and surface exclusion, which has homology with lambda DNA

Summary Escherichia coli K12 cells carrying a cloned 1.4 kb HindIII fragment from plasmid ColV2-K94, showed increased survival in guinea pig serum. The recombinant plasmid also conferred group II surface exclusion, i.e. the cells were reduced in recipient ability towards the incoming plasmid R538drd in conjugation experiments. Southern blotting suggested homology with bacteriophage lambda DNA and to the insertion element IS2. Determination of the DNA sequence of the fragment demonstrated the presence of a truncated IS2 (165 bp), separated by 250 bp from a 900 bp stretch of homology with lambda DNA, beginning within the Rz gene and continuing in the rightward direction on the lambda map. A 97 amino acid open reading frame (ORF) adjacent to Rz and on the opposite strand, remained intact in iss, with several amino acid changes. The ORF in iss is preceded by sequences resembling prokaryotic ribosome binding sites and promoters.     

Microbial transformation of rifamycin B: A new extracellular oxidase fromCurvularia lunata

Summary A highly active extracellular rifamycin oxidase was isolated fromCurvularia lunata var.aeri. The enzyme has a pH optimum of 6.5 and temperature optimum of 50°C.     

A physical and genetic map of the IncFI plasmid ColV2-K94

A restriction enzyme map of the IncFI plasmid ColV2-K94 was generated using EcoRI, BamHI, HindIII, and XhoI; the genetic features of this element were then mapped from previous heteroduplex studies.     

Molecular epidemiology of plasmid patterns in Shigella dysenteriae type I obtained from an outbreak in West Bengal (India)

Abstract Multiple antibiotic-resistant Shigella dysenteriae type 1 isolates from a recent epidemic in West Bengal (India) showed identical plasmid patterns. All isolates were resistant to ampicillin (Am), chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm) and trimethoprim (Tp) and contained 6 plasmids, ranging from 2.5–120 kb. The Am resistance determinant was located on the 120 kb plasmid. This plasmid was unstable when the S. dysenteriae strains were grown above 37°C. The Bangladesh strains of S. dysenteriae type 1 showed identical plasmid patterns, except that many isolates were Am-sensitive and lacked the 120 kb plasmid. In strains from both Bangladesh and West Bengal, predominantly group-B plasmids conferred resistance to Cm and Tc. Comparisons of Eco R1 fragments generated from the total plasmid DNA content of each strain support the view that the plasmids present in the S. dysenteriae type 1 strains isolated from all recent epidemics in India and Bangladesh were identical.     

Crystallographic,morphological and photoluminescent investigations of Tb3+-doped YAlO3 perovskites for lighting applications

Terbium(III)-doped yttrium aluminate perovskite (YAP:xTb³⁺) (x = 0.01–0.08 mol) was synthesized using a simple gel-combustion method. Structural elucidations were performed using X-ray diffraction (XRD) and Rietveld analysis. Fourier-transform infrared spectral studies validated the efficient synthesis of designed doped samples. Transmission electron microscopic images showed the agglomerated irregular dimensions of the synthesized nanocrystalline materials. When excited at 251 nm, a strong emissive line attributed to ⁵D₄ → ⁷F₅ electronic transition was observed at 545 nm (green emission). The maximum luminescence was found at the optimized concentration (0.05 mol) of Tb³⁺ ions; this emission was quenched by dipolar–dipolar (d–d) interactions. Chromaticity (x and y) and correlated colour temperature parameters were obtained by analysing the emission profiles. Finally, the colour coordinates of nanophosphors were closer to the National Television Standards Committee green coordinates, which replicates their potency in the design and architecture of R-G-B-based white LEDs.     

Genome characterization of glucose-isomerase-producingStreptomyces sp. NCIM 2730: detection of sequences homologous to a rice repeat sequence

Restriction analysis of the genomic DNA from a high glucose/xylose-isomerase-yieldingStreptomyces sp. NCIM 2730 revealed a number of distinct bands on a background smear, indicating the occurrence of repeated DNA sequences in the genome. Optical renaturation analysis indicated that 25% of the genome comprised rapidly reannealing sequences with a copy number of 50 and a kinetic complexity of 3×10³. Hybridization of theStreptomyces genomic library with theStreptomyces DNA, supported the estimate of the repetitive DNA content derived from the re-association kinetics of the DNA. Hybridization of DNA from three differentStreptomyces species with a rice repetitive DNA probe revealed the presence of homologous sequences, which is a unique finding.M.S. Ghatge was and V.V. Deshpande and P.K. Ranjekar are with the Division of Biochemical Sciences, National Chemical Laboratory, Pune -41108, India; M.S. Ghatge is now with the Department of Microbiology & Molecular Biology, The University of Kansas Medical Center, 36th and Rainbow Blvd, Kansas City, Kansas - 66103, USA.     

An active-site carboxyl group in liquefying α-amylase: specific chemical modification

Bacillus amyloliquefaciens -amylase activity is pH-dependent and the plot log (Vmax/Km) versus pH implicated a carboxyl group of aspartic acid/glutamic acid at the active site. Chemical modification of -amylase with EDC confirmed this view. Further, analysis of inactivation kinetics showed that modification of a single carboxyl group led to complete loss of the enzymic activity.     

Isopongaglabol and 6-methoxyisopongaglabol,two new hydroxyfuranoflavones from Pongamia glabra

Isopongaglabol and 6-methoxyisopongaglabol, two new hydroxyfuranoflavones, together with two furanoflavones 5-methoxyfurano(8,7-4″,5″)flavone and 5-methoxy-3′,4′-methylenedioxyfurano(8,7-4″,5″)flavone, two simple flavones, desmethoxykanugin and fisetin tetramethyl ether, a chromenoflavanone, ovalichromene B, two triterpenes, cycloart-23-ene-3β,25-diol and friedelin, and β-sitosterol-β-d-glucoside were isolated from the petrol and CHCl₃ extracts of the flowers of Pongamia glabra. The structures of isopongaglabol and 6-methoxyisopongaglabol have been established as 4′-hydroxyfurano(8,7-4″,5″)flavone and 4′-hydroxy-6-methoxyfurano(8,7-4″,5″)flavone, respectively, on the basis of the spectral evidence and they have been confirmed by synthesis.