A clone of Leptospira interrogans sensu stricto is the major cause of leptospirosis in the archipelago of Andaman and Nicobar Islands, India

AIMS: Andaman and Nicobar Islands in India has a century long history of human leptospirosis. Several isolates have been recovered over the years from different locations. The present study was undertaken to understand the clonal relationship between all these pathogenic leptospires recovered from these islands. METHODS AND RESULTS: Arbitrarily primed polymerase chain reaction (AP-PCR) was employed to genetically characterize 40 isolates recovered during 1995--2001 and their fingerprints were compared with those of 26 reference strains of known genetic and serological affinities. Sequences of PCR-amplified products from representative isolates were compared with those of different strains belonging to seven genospecies. AP-PCR fingerprints revealed that 32 of the 40 isolates were clonal in nature and fingerprints of all the isolates matched with known reference strains of pathogenic Leptospira interrogans sensu stricto. Comparison of sequence data of PCR amplified products of reference strains and isolates also corroborated these findings. CONCLUSIONS: The study revealed that 80% of the isolates recovered from these islands were clonal in nature and all the isolates taken in the study belonged to Leptospira interrogans sensu stricto. SIGNIFICANCE AND IMPACT OF THE study: An extension of the study in animal population would help in understanding the transmission dynamics of this commonly circulating clone in these islands, which in turn might help in effective control of this public health problem.     

Symbiotic efficiency and infectivity of an autochthonous arbuscular mycorrhizal Glomus sp. from saline soils and Glomus deserticola under salinity

 The purpose of this study was to compare the effect of salinity on the symbiotic efficiencies and mycelial infectivity of two arbuscular mycorrhizal fungi (AMF), one isolated from saline soils (Glomus sp.) and the other (Glomus deserticola) from nonsaline soils (belonging to the Estación Experimental del Zaidín collection). Lettuce plants inoculated with either of these two fungi or maintained as uninoculated controls were grown in soil with three salt concentrations (0.25, 0.50 or 0.75 g NaCl kg^–1 dry soil). Both AMF protected host plants against salinity. However, when the results of shoot dry weight and nutrient contents were expressed relative to the total length of mycorrhiza formed, it was found that both AMF differed in their symbiotic efficiencies. These differences were more evident at the two highest salt levels. Glomus sp.-colonized plants grew less and accumulated less N and P, whereas they formed a higher amount of mycorrhiza. The mechanism by which Glomus sp. protected plants from the detrimental effects of salt was based on the stimulation of root development, while the effects of G. deserticola were based on improved plant nutrition. The increase in salinity of soil decreased the hyphal growth and/or viability of Glomus sp. to a higher extent than those of G. deserticola since the mycelial network generated by G. deserticola was more infective than that of Glomus sp. Accepted: 8 September 2000     

Genomic characterization of thermophilic Geobacillus species isolated from the deepest sea mud of the Mariana Trench

The thermophilic strains HTA426 and HTA462 isolated from the Mariana Trench were identified as Geobacillus kaustophilus and G. stearothermophilus, respectively, based on physiologic and phylogenetic analyses using 16S rDNA sequences and DNA–DNA relatedness. The genome size of HTA426 and HTA462 was estimated at 3.23–3.49 Mb and 3.7–4.49 Mb, respectively. The nucleotide sequences of three independent -phage inserts of G. stearothermophilus HTA462 have been determined. The organization of protein coding sequences (CDSs) in the two -phage inserts was found to differ from that in the contigs corresponding to each insert assembled by the shotgun clones of the G. kaustophilus HTA426 genome, although the CDS organization in another insert is identical to that in the HTA426 genome.     

Optimization of cellulase-free xylanase production by a novel yeast strain

Summary A novel yeast strain, NCIM 3574, isolated from a decaying wood produced up to 570 IU ml^–1 of xylanolytic enzymes when grown on medium containing 4% xylan. The yeast strain also produced xylanase activity (40–50 IU ml^–1) in the presence of soluble carbon sources like xylose or arabinose. No xylanase activity was detected when the organism was grown on glucose. The crude xylanase preparation showed no activity towards cellulolytic substrates but low levels of -xylosidase (0.1 IU ml^–1) and -l-arabinofuranosidase (0.05 IU ml^–1) were detected. The temperature and pH optima for the crude xylanase preparation were 55°C and 4.5 respectively. The crude xylanase produced mainly xylose from xylan within 5 min. Prolonged hydrolysis of xylan produced xylobiose and arabinose, in addition to xylose, as the end products. The presence of arabinose as one of the end products in xylan hydrolysate could be due to the low levels of arabinofuranosidase enzyme present in the crude fermentation broth.     

盾叶薯蓣内生真菌Dzf13抗细菌活性成分

采用活性追踪分离的方法,从盾叶薯蓣内生真菌菌株Dzf13中分离到两个具抗细菌活性的化合物1和2,经理化和波谱分析鉴定为麦角甾-5,7,22-三烯-3β-醇(1)和5α,8α-过氧麦角甾-6,22-二烯-3β-醇(2).结果表明,化合物1和2对根癌土壤杆菌、黄瓜角斑病菌和番茄疮痂病菌等三种植物病原细菌的生长均表现出一定的抑制活性,尤其对黄瓜角斑病菌的抑制活性较强.结果还表明5α,8α-过氧麦角甾-6,22-二烯-3β-醇(2)的抗细菌活性要比麦角甾-5,7,22-三烯-3β-醇(1)强.     

Experimental rat vaginal infection with Candida parapsilosis

The experimental vaginopathic potential of Candida parapsilosis was determined in ovariectomized rats maintained under pseudoestrus by estrogen administrations. Of the 3 strains of C. parapsilosis tested, that isolated from the vagina of a woman affected by vulvovaginal candidosis gave a prolonged and sustained experimental vaginitis, not different in extent and duration from that caused by a vaginal isolate of C. albicans from a vaginitis patient. The other two isolates of C. parapsilosis (one from the vagina of an asymptomatic subject and another from soil) were unable to infect rat vagina. Microscopic observations of PAS-stained vaginal smears from rats infected with the vaginopathic isolate of C. parapsilosis showed pronounced adherence of yeasts to exfoliated cells. In addition, this isolate of C. parapsilosis produced an elevated quantity of acid proteinase in vitro.     

The structure of the Ni-Fe site in the isolated HoxC subunit of the hydrogen-sensing hydrogenase from Ralstonia eutropha

The regulatory Ni-Fe hydrogenase (RH) from Ralstonia eutropha which forms a [HoxBC]2 complex functions as a hydrogen sensor under aerobic conditions. We have studied a novel Strep-tag isolate of the RH large subunit, HoxC(ST), which lacks the Fe-S clusters of HoxB, allowing for structure determination of the catalytic site by X-ray absorption spectroscopy both at the Ni and, for the first time, also at the Fe K-edge. This technique, together with Fourier-transform infrared spectroscopy, revealed a Ni-Fe site with [O1(CysS)2Ni(II)(mu-SCys)2Fe(II)(CN)2(CO)] structure in about 50% of HoxC(ST) and a [(CysS)2Fe(II)(CN)2(CO)] site lacking Ni in the remainder protein. Possibly both sites may be intermediates in the maturation process of the RH.     

Oxygen protection of nitrogenase in Frankia sp. HFPArI3

O₂ protection of nitrogenase in a cultured Frankia isolate from Alnus rubra (HFPArI3) was studied in vivo. Evidence for a passive gas diffusion barrier in the vesicles was obtained by kinetic analysis of in vivo O₂ uptake and acetylene reduction rates in response to substrate concentration. O₂ of NH ₄ ⁺ -grown cells showed an apparent K _m O₂ of approximately 1M O₂. In N₂-fixing cultures a second K _m O₂ of about 215 M O₂ was observed. Thus, respiration remained unsaturated by O₂ at air-saturation levels. In vivo, the apparent K _m for acetylene was more than 10-fold greater than reported in vitro values. These data were inter oreted as evidence for a gas diffusion barrier in the vesicles but not vegetative filaments of Frankia sp. HFPArI3.     

香蕉束顶病毒基因克隆和序列分析

对香蕉束顶病毒（ＢＢＴＶ）中国分离株ＤＮＡ组份Ｉ（ＤＮＡ－１）、外壳蛋白（ＣＰ）和运转蛋白（ＭＰ）基因进行了克隆和序列分析。ＢＢＴＶＤＮＡ－１含有１１０３个核苷酸,与南太平洋和亚洲分离株分别有８７％－８８％ ９６．９－９８％的核苷酸序列同源性。由ＤＮＡ－１编码的复制酶含有１８６个在酸残基。与南太平洋和亚洲分离株分别有８４．４％－９５．８％和９７．６％、９８．０％的氨基酸序列同源性。外壳蛋白基因由５     

福州地区对虾白斑病病毒的超微结构

在福州地区分离到一种高致病性的白斑病病毒 ,该病毒仅存在于细胞质中 ,完整的病毒粒子有囊膜 ,一端略圆 ,一端稍尖 ,直径约为 80～ 10 0nm ,囊膜与核衣壳之间的间隙约为 2 0～ 2 5nm。该病毒在细胞内不形成包含体 ,但有些可形成封入体。负染观察到的病毒核衣壳呈直杆状 ,但长度和直径相差较大 ,最长的病毒超过 6 0 0nm。这些特征与其它已报道的白斑病病毒有所不同 ,因此暂将它称为“对虾白斑病病毒福州分离株”。