Purification and regulation of glutamine synthetase in a collagenolytic Vibrio alginolyticus strain

Glutamine synthetase (EC 6.3.1.2) has been purified from a collagenolytic Vibrio alginolyticus strain. The apparent molecular weight of the glutamine synthetase subunit was approximately 62,000. This indicates a particle weight for the undissociated enzyme of 744,000, assuming the enzyme is the typical dodecamer. The glutamine synthetase enzyme had a sedimentation coefficient of 25.9 S and seems to be regulated by a denylylation and deadenylylation. The pH profiles assayed by the -glutamyltransferase method were similar for NH₄-shocked and unshocked cell extracts and isoactivity point was not obtained from these eurves. The optimum pH for purified and crude cell extracts was 7.9. Cell-free glutamine synthetase was inhibited by some amino acids and AMP. The transferase activity of glutamine synthetase from mid-exponential phase cells varied greatly depending on the sources of nitrogen or carbon in the growth medium. Glutamine synthetase level was regulated by nitrogen catabolite repression by (NH₄)₂SO₄ and glutamine, but cells grown, in the presence of proline, leucine, isoleucine, tryptophan, histidine, glutamic acid, glycine and arginine had enhanced levels of transferase activity. Glutamine synthetase was not subject to glucose, sucrose, fructose, glycerol or maltose catabolite repression and these sugars had the opposite effect and markedly enhanced glutamine synthetase activity.Abbreviations GS glutamine synthetase - SMM succinate minimal medium - ASMM ammonium/succinate minimal medium - GT -glutamyl transferase - SVP snake venom phosphodiesterase     

Changes in virulence of waterborne enteropathogens with chlorine injury

We designed experiments to assess the effect of chlorine injury on the virulence of waterborne enteropathogens. Higher chlorine doses (0.9 to 1.5 mg/liter) were necessary to produce injured Yersinia enterocolitica, Salmonella typhimurium, and Shigella spp. than to produce injured enterotoxigenic Escherichia coli or coliform bacteria (0.25 to 0.5 mg/liter) in the test system used; 50% lethal dose experiments in which mice were used showed that injured Y. enterocolitica cells were 20 times less virulent than uninjured control cells (3,300 and 160 CFU, respectively). This decrease in virulence was not related to reduced attachment to Henle 407 intestinal epithelial cells, but could be related to a loss of HeLa cell invasiveness. In contrast, injured S. typhimurium and enterotoxigenic E. coli cells lost their ability to attach to Henle cells. These data show that some enteropathogens and coliform bacteria differ in their sensitivities to chlorine injury and that the virulence determinants affected by chlorine may vary from one pathogen to another.     

Isolation of cellulolytic mutants of thermotolerant fungus Chaetomium cellulolyticum ATCC 32319

Spores of Chaetomium cellulolyticum were treated with 200 micrograms/ml of N-methyl-N'-nitro-N-nitrosoguanidine and seven mutants producing clear zones around their colonies on modified Vogels medium were isolated. Mutant NG7 showed altered morphological characteristics and produced more cellulases (CMCase--15 units, FPA--6.5 units, CDA--0.80 units and cellobiase--4.7 units/ml) than its parental strain (CMCase--10 units, FPA--4.5 units, CDA--0.36 units and cellobiase--2.7 units/ml). Cellulase preparation was used to saccharify rice straw, wheat straw, bagasse and sawdust, pretreated with 1% sodium hydroxide.     

Subunit structure of human and rat glutathione S-transferases

In rat tissues different forms of glutathione (GSH) S-transferases represent various dimeric combinations of at least four different classes of subunits categorized on the basis of their Mr values as seen on polyacrylamide gels. These subunit types represent heterogeneous populations and the actual number of subunits in rat GSH S-transferases may be far more than is known at present. Human GSH S-transferases arise from dimeric combinations of at least four immunologically and functionally distinct subunits which can be classified into three types, A (Mr 26,500), B (Mr 24,500) and C (Mr 22,500). There is evidence for considerable charge heterogeneity in each of these subunit types.     

Studies on mitotic and salivary chromosomes of Dacus cucurbitae Coquillett (Diptera: Trypetidae)

Dacus cucurbitae is a serious pest of various types of fleshy fruits and vegetables. The mitotic and salivary chromosomes were reinvestigated using the air-drying and different (C-and H-) banding techniques with a view to rectify the existing controversy regarding the Indian populations of this species. A standard map of its salivary chromosomes was constructed and some important identifiable landmarks were recognized in each arm.     

Emergence of some caddisflies (Trichoptera) from a wooded stream in southern Ontario

Twenty-eight species of nine families of caddisflies (Trichoptera) were identified in 170 samples taken over an 8-month period from five emergence traps placed on a second-order, forested, cold-stenothermal stream on the Niagara Escarpment, Ontario, Canada.A mean of 980.9 caddisflies m^–2 of streambed was obtained over the entire sampling period. Eleven common species accounted for 92.8% of the total emergence with specific proportions ranging from 23.8% (Wormaldia moesta) to 0.11 % (Rhyacophila sp.). The use of various kinds of traps in other studies and their effects on the detection of species composition and abundance are discussed and compared with the present study.Although the distributions of all the common species were invariant over time, four species showed low to high degrees of patchiness in the streambed; the other seven common species were uniformly distributed. However, a large residual variance suggested a subtle mechanism of microhabitat selection by the larvae and (or) pupae, not detectable by even the small emergence traps used.Both sexes of 15 species, only males of 4 and only females of 9 species were collected. Eight of the eleven common species showed significant departures from a balanced sex ratio and five exhibited a protandry of from 1 to 3 weeks. Neither this study nor others have been able to establish a predictable pattern of sex ratios in Trichoptera.The emergence periods and patterns of the eleven common species are described and compared with other studies. Of these common species, one emerged in the spring, seven during the summer and three during the late summer or early fall. Ten species had a short emergence period with a distinct peak and a significantly skewed pattern. One species,Parapsyche apicalis, exhibited a prolonged emergence period, no distinct peak and a significantly platykurtotic² pattern. With the exception ofLepidostoma sp. A, the emergence patterns of the common species were unimodal.     

Biological control of citrus mealybug,Planococcus citri with an introduced parasite,Leptomastix dactylopii in India

Planococcus citri (Risso) is one of the major pests of citrus orchards in India. For the control ofP. citri, an encyrtid parasite,Leptomastix dactylopii How. was introduced from West Indies in 1983. The parasite was mass bred and inoculative releases were made in 2 selected citrus orchards where infestation of mealybug on fruits (sweet orange, seedless lime and acid lime) ranged from 38 to 65 per cent. Establishment of the parasite in the 2 release orchards resulted in complete control of the mealybug within 3 to 4 months. No insecticidal sprays were required subsequently for the control ofP. citri in the following seasons. Contribution No. 152/85 of the IIHR, Bangalore — 560089.     

Utilization of wild relatives in the genetic improvement of Arachis hypogaea L.

Summary Synthetic amphidiploids were established in 32 combinations involving 8 diploid wild species representing both A and B genomes of section Arachis. Bivalent and multivalent associations in the amphidiploids of 7 A genome species confirm that these species have identical genomes. Contrastingly, high bivalent frequencies in amphidiploids involving the A and B genome species suggest that A. batizocoi has a distinct B genome that is partially homologous to the other genome A represented in the rest of the species. Crossability, chromosome pairing and pollen and pod fertility in hybrids between A. hypogaea and amphidiploids have revealed that these amphidiploids can be used as a genetic bridge for the transfer of genes from the wild species into the cultivated groundnut.Submitted as Journal Article No. 530 by International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)     

Comparison of single seed descent,selective intermating and mass selection for seed size in greengram (Vigna radiata (L.) Wilczek)

Summary Three selection methods (single seed descent (SSD), mass selection and selective intermating) were applied simultaneously to a highly heterogeneous and broadly based population of greengram. Progeny developing after two cycles of selection were evaluated for yield and seven other economic characters. The relative efficacy of each selection method was judged on the basis of the number of high yielding progeny, mean yield of top 10% progeny, and mean of the highest yielding progeny. Selection after two cycles of selective intermating was found to be the best method for generating productive progeny although mass selection favouring smaller seeds was an equally efficient method. Both of these were found superior to SSD selection.