Tunicamycin-resistant mutants of Bacillus amyloliquefaciens are deficient in amylase, protease and penicillinase synthesis and have altered sensitivity to antibiotics and autolysis

Mutants of Bacillus amyloliquefaciens resistant to at least 10 micrograms/ml of tunicamycin were isolated and shown to be pleiotropic. The mutants were more resistant to streptomycin, chloramphenicol, kanamycin and neomycin than was the parent strain but less resistant to penicillin G and tetracycline. They were more autolytic, presumably due to an altered cell wall. The mutants produced reduced levels of amylase, penicillinase and both metal and serine protease besides having an enhanced sporulation frequency and being more motile.     

The human endonexin II (ENX2) gene is located at 4q28----q32

A relatively recently identified family of structurally similar Ca2(+)-dependent phospholipid binding proteins is called the annexin gene family. At least seven genes are known, although their exact functions are unclear. The endonexin II gene (ENX2), one member of the gene family, is assigned to 4q28----q32 using both Southern transfer analysis of human x rodent somatic cell hybrid DNAs and in situ chromosome hybridization. One of the lipocortin II genes, another annexin, had previously been assigned to the long arm of chromosome 4.     

Binding of thiocyanate to lactoperoxidase: 1H and 15N nuclear magnetic resonance studies

The binding of thiocyanate to lactoperoxidase (LPO) has been investigated by 1H and 15N NMR spectroscopy. 1H NMR of LPO shows that the major broad heme methyl proton resonance at about 61 ppm is shifted upfield by addition of the thiocyanate, indicating binding of the thiocyanate to the enzyme. The pH dependence of line width of 15N resonance of SC15N- in the presence of the enzyme has revealed that the binding of the thiocyanate to the enzyme is facilitated by protonation of an ionizable group (with pKa of 6.4), which is presumably distal histidine. Dissociation constants (KD) of SC15N-/LPO, SC15N-/LPO/I-, and SC15N-/LPO/CN- equilibria have been determined by 15N T1 measurements and found to be 90 +/- 5, 173 +/- 20, and 83 +/- 6 mM, respectively. On the basis of these values of KD, it is suggested that the iodide ion inhibits the binding of the thiocyanate but cyanide ion does not. The thiocyanate is shown to bind at the same site of LPO as iodide does, but the binding is considerably weaker and is away from the ferric ion. The distance of 15N of the bound thiocyanate ion from the iron is determined to be 7.2 +/- 0.2 A from the 15N T1 measurements.     

Hydroxylation of benzoate and its chlorinated derivatives in Aspergillus niger

Comparison of the properties of a purified benzoate-4-hydroxylase, using benzoic acid and its chlorinated derivatives as substrate, suggests that the same enzyme operates during the initial hydroxylation of benzoate, 2-chlorobenzoate (2-cba), and 3-chlorobenzoate (3-cba) in A.niger.     

Monoclonal antibody-based immunoassay for type A Clostridium botulinum toxin is comparable to the mouse bioassay

A monoclonal antibody (BA11) has been produced against Clostridium botulinum type A neurotoxin by the fusion of myeloma cells (P3 NS1/1-Ag4-1) with spleen cells from BALB/c mice immunized with botulinum type A neurotoxoid. The antibody bound specifically to botulinum type A neurotoxin, showing no cross-reactivity with types B and E botulinum toxins or with any of several other bacterial toxins tested. The monoclonal antibody did not bind to botulinum type A neurotoxin which had been denatured with sodium dodecyl sulfate and bound only weakly to each of the separated heavy and light subunits of the neurotoxin, suggesting a conformational requirement for the antigenic determinant of the antibody. A sensitive immunoassay for C. botulinum type A toxin with monoclonal antibody BA11 in conjunction with an enzyme amplication system has been developed which allows detection of 5 to 10 mouse 50% lethal doses ml-1 of purified neurotoxin. The assay was equally sensitive when applied to the detection of crude toxin in food stuffs; the average value for the minimum level of detectable toxin in extracts of tinned salmon or corned beef was 9 +/- 3.1 mouse 50% lethal doses ml-1.     

Functional relationship between ammonia and gangliosides in brain

The functional significance of ammonia production in brain under physiological or pathological conditions is not clearly known. NH₄ ⁺ stimulates Na⁺, K⁺ activated ATPase causing stabilization of neuronal membranes of which gangliosides are major structural components. Moreover ammonia is known to inhibit lysosomal enzymes which include enzymes degrading gangliosides. Gangliosides have been shown to stimulate neuritogenesis in neuronal cultures and prevent the damage of the neurons from glutamate toxicity particularly in areas of brain ischemia. Hyperammonemia without any behavioural changes was induced in experimental rats by intraperitoneal administration of either a single dose (0.8 mmol/100 g wt.) or by six hourly doses (0.6 mmol/100 g wt.) of ammonium acetate. An increase in the content of gangliosides along with a rise in the content of GD_1A and GD_1B without any change in -galactosidase and N-acetylhexosaminidase was observed in cerebral cortex, cerebellum, and brain stem, following the administration of single dose of ammonium acetate. Gangliosides, after extraction from the different brain regions, were estimated by the thiobarbituric acid method and expressed in terms of sialic acid. Individual gangliosides were separated and estimated by thin layer chromatography using resorcinol as the staining agent. These results suggest that ammonia production in the neuronal pathways in brain either as a result of repeated stimulation under physiological conditions or as a result of focal ischemia or injury, may likewise cause an increase in the content of gangliosides which may help in neuritic growth (physiological conditions facilitating synaptic plasticity) and may exert a protective effect on the neurons in the ischemic area against glutamate toxicity.Former Professor of Biochemistry, OMC, Hyderabad.     

Heterogeneity in the concerted evolution process of a tandem satellite array in meadow mice (Microtus)

The evolutionary history of a 160-bp tandem satellite array, originally described from Microtus chrotorrhinus and called MSAT-160, was examined in related species of arvicolid rodents by sequence analyses, quantitative dot blotting, and Southern blotting. Results indicate that MSAT-160 is present in 12 of the 20 species and subspecies of Microtus assayed, but not in species belonging to any of the eight other genera examined. DNA from each species containing MSAT-160 was digested with 12 restriction endonucleases and restriction patterns were obtained reflecting the variable extent of homogenization of any given variant in different species. For example, with MboI digestion, M. chrotorrhinus produced a type A ladder pattern where most monomers contain the restriction site, M. ochrogaster generated a type B pattern where most monomers lack the site, and M. agrestis yielded a pattern intermediate between the A and B types. Further, dot blotting revealed copy-number differences between species. These findings indicate that changes in the periodic structure and amount of satellite DNA have occured since these species last shared a common ancestor. In addition, various species-pacific patterns were documented, illustrating that mechanism other than genomewide homogenization, such as stochastic mutation, out-of-register crossing over, deletion, and random amplification also play a role in structuring tandem arrays. Stochastic mutation and homogenization rates in satellite DNA, levels of species diversity, and magnitudes of chromosomal divergence differ significantly in Microtus, Mus, and Ctenomys, the three rodent lineages examined.