Standardization of parameters for the mycobacillin synthetase activity

An effective method of preparation involving sonication was developed for cell-free mycobacillin synthetase fromBacillus subtilis. The enzyme showed optimum activity at a buffer concentration of 50 mM (Tris-HCl) and pH 7.5. ATP and Mg²⁺ which were essential for synthesis showed an optimum requirement at a ratio of 1∶1. The synthetase was markedly inhibited by ADP whereas AMP was without any effect. ATP or ATP-generating system could not be replaced by GTP, UTP or CTP. Co²⁺ and Mn²⁺ could to some extent substitute Mg²⁺. Mercapto reagents inhibited the antibiotic synthesis. Exogenous addition of pantothenic acid had no effect.     

Suppression of Two Missense Alleles of the TRP5 Locus of SACCHAROMYCES CEREVISIAE

A suppressor SUP101 of alleles trp5-67 and trp5-18 of the trp5 locus of Saccharomyces cerevisiae is described. The two suppressible mutations have been previously classified as missense. The suppression does not result from a physiological bypass of the tryptophan synthetase-catalyzed reaction, since the suppression is allele-specific. IU alleles trp5-70, tryp5-95, and trp5-102; IA alleles trp5-81, trp5-101, and trp5-103; and the ochre alleles trp5-33 and trp5-48 are not suppressed by SUP101. SUP101 does not suppress ochre alleles ade2-1, his5-2, arg4-17, lys1-1, amber alleles trp1-1, tyr7-1, or unclassified alleles at a number of other loci. These results indicate SUP101 is a missense suppressor. Growth on tryptophanless media is dependent upon gene dosage of both the suppressor and the suppressible alleles. Only the diploids homozygous both for the suppressor and suppressible alleles produce growth equivalent to growth of the haploids bearing a suppressible allele and the suppressor. Suppressor-bearing strains grow poorly even on tryptophan-supplemented media. In more than 100 asci analyzed partial growth inhibition on the complete medium always segregated with the suppressor.     

Kinetoplastid flagellates: surface-reactive carbohydrates detected by fluorescein-conjugated lectins

Membrane-associated carbohydrate residues of 3 isolates of Leishmania derived from etiological agents of visceral leishmaniasis (VL), postkala-azar dermal leishmaniasis (PKDL), and cutaneous leishmaniasis (CL), as well as 2 other nonpathogenic insect gut kinetoplastid flagellates, Bodo sp. and Herpetomonas sp., were characterized with the aid of 8 fluorescein-conjugated lectins. Four lectins, concanavalin A, Dolichos biflorus, phytohemagglutinin P, Ricinus communis agglutinin, bound to all kinetoplastid flagellates at different concentrations. All Leishmania promastigotes showed reactions with Ulex agglutinin. Although these lectins were bound to all kinetoplastids, the site and intensity of binding was different. All skin-dwelling Leishmania parasites, viz., Leishmania donovani of PKDL and Leishmania tropica of CL showed unique selectivity toward peanut agglutinin (PNA), soybean agglutinin, and wheatgerm agglutinin (WGA). More interestingly, Herpetomonas showed positive fluorescence with PNA and WGA, whereas Bodo was negative. The results demonstrated that no lectin could distinguish between the pathogenic and nonpathogenic status of kinetoplastid flagellates. Moreover, the antigenic (carbohydrate) profiles of Herpetomonas corresponded more closely to those of L. tropica, whereas Bodo shared some common lectin receptors with L. donovani of VL.     

Leishmania donovani: a chemically defined medium suitable for cultivation and cloning of promastigotes and transformation of amastigotes to to promastigotes

A chemically defined medium using commercially available alpha-MEM supplemented with hemin, HEPES, L-glutamine, D-glucose, folic acid, D-biotin and adenine supports the luxuriant growth and propagation of Leishmania donovani promastigotes. A peak parasite population of about 7.0 x 10(7)/ml at stationary phase and a population doubling time of 11.4 h for high-subpassage promastigotes were obtained. The medium was suitable for transformation of isolated amastigotes from infected hamster spleen. Promastigotes could be detected by culturing kala-azar patients' bone-marrow aspirate or spleen puncture material in this medium. Four out of six freshly transformed isolates gradually adapted and grew well in this medium. Macroscopic colonies appeared on agar plates prepared with the medium within 16-20 days after inoculation. The cloning efficiency was increased about five-fold by glycerol supplementation.     

Sequence analysis of duplicated actin genes in Lagenidium giganteum and Pythium irregulare (Oomycota)

Southern analysis of genomic DNA identified multiple-copy actin gene families in Lagenidium giganteum and Pythium irregulare (Oomycota). Polymerase chain reaction (PCR) protocols were used to amplify members of these actin gene families. Sequence analysis of genomic coding regions demonstrated five unique actin sequences in L. giganteum (Lg-Ac 1, 2, 3, 4, 5) and four unique actin sequences in P. irregulare (Pi-Acl, 2, 3, 4); none were interrupted by introns. Maximum parsimony analysis of the coding regions demonstrated a close phylogenetic relationship between oomycetes and the chromophyte alga Costaria costata. Three types of actin coding regions were identified in the chromophyte/oomycete lineage. The type 1 actin is the single-copy coding region found in C. costata. The type 2 and type 3 actins are found in the oomycetes and are the result of a gene duplication which occurred soon after the divergence of the oomycetes from the chromophyte algae. The type 2 coding regions are the single-copy sequence of Phytophthora megasperma, the Phytophthora infestans actB gene, Lg-Ac5 and Pi-Ac2. The type 3 coding regions are the single-copy sequence of Achlya bisexualis, the P. infestans actA gene, Lg-Ac1, 2, 3, 4 and Pi-Acl, 3, 4. Correspondence to: D. Bhattacharya     

Inhibition of seed germination by Macrophomina phaseolina is related to phaseolinone production

The production of phaseolinone, a phytotoxic metabolite of Macrophomina phaseolina in infected Phaseolus mungo seeds grown on soil, was estimated by enzyme-linked immunosorbent assay and HPLC. The degree of inhibition of seed germination correlated well with the amount of toxin produced; 50% inhibition was observed at a toxin level of 2.1 μg g^-1 of wet tissue. A comparison of the toxin-producing ability of nine isolates of the fungus obtained from different hosts and localities showed that the strain MPK'83 produced a significantly larger amount of the toxin, both in liquid culture and in infected seeds. The virulence of the isolates was related to their ability to produce phaseolinone.