Acridine Sensitivity of Bacteriophage T2H in Escherichia coli

Normally acridine-sensitive, Escherichia coli-T2H complexes are rendered acridine-resistant if the infecting bacteriophage mutant is either pr or q. If these pr or q mutants are treated to produce sensitive revertants, one obtains a mutation at any of several dye-sensitizing (ds) sites in the early enzyme region of the T2 map. The ds mutants are nonspecific suppressors because they reduce the resistance of complexes containing either pr or q to proflavine. The ds mutants are not identical in action, since some make pr or q sensitive to proflavine and quinacrine, and others, to proflavine alone. Two ds mutants have r to r(+) mutation patterns which differ, depending upon whether or not the ds is coupled with r7 (an rII mutant). The mutation patterns of r(+) to r are the same for both ds mutants and for wild type. We suggest that dye sensitization may consist of alterations of early enzymes so as to produce slightly different forms of deoxyribonucleic acid which are in turn dyesensitive.     

Properties and attempted culture of Pasteuria penetrans, a bacterial parasite of root-knot nematode (Meloidogyne javanica)

When they were subjected to a range of physical and chemical treatments, spores of Pasteuria penetrans showed properties similar to those of other endospore-forming bacteria. The spores did not take up some stains, were resistant to desiccation and sonication and showed extrusion of spore contents ('spore popping') on prolonged exposure to 0.1% KMnO₄ in 0.3 n HNO₃. Calcium and dipicolinic acid (DPA) were present at concentrations of 0.28% and 0.96% of the spore dry weight respectively, giving a Ca: DPA molar ratio of 1.2. The infectivity of P. penetrans spores was reduced to a low level after heating at 100°C for 5 min, but spore attachment was not markedly affected by heating at 100°C for 15 min. Evidence for the presence of catalase in P. penetrans spores was equivocal because the low levels of catalase activity observed in spore suspensions may have been due to contamination from catalase-positive nematode tissue. When P. penetrans spores were exposed to a range of substances known to act as germinants for spores of Bacillus spp., germination or loss of refractility was not observed by phase microscopy. In vitro culture of P. penetrans was attempted by inoculating either spores or vegetative mycelial bodies onto a diverse range of simple and complex media and incubating them in aerobic, reduced oxygen, anaerobic and increased CO₂ environments. Signs of spore germination or growth of vegetative stages were never observed.     

Monoclonal Antibodies for Detection and Serotyping of Cucumber Mosaic Virus

Two monoclonal antibodies (MAbs) to cucumber mosaic virus (CMV) were selected from a panel of MAbs for use in the direct DAS (double antibody sandwich)-ELISA. Two different test procedures were developed: an ELISA with polyclonal and monoclonal antibodies (mixed ELISA) for the routine detection of CMV and a MAb-ELISA with two MAbs directed against different epitopes for the specific detection of the N serotype which is prevalent in GDR. The conventional two-step incubation of plates precoated with IgG was compared with simultaneous incubation of test sample and labelled antibody (one-step incubation). The mixed ELISA proved to be more sensitive than the direct DAS-ELISA with polyclonal antisera in detecting CMV in crude sap of infected plants. On the other hand, the MAb-ELISA could be used for serotyping of CMV isolates which is important in epidemiological investigations and in resistance breeding. Both the two-step and the one-step procedures gave similar results with some advantages of the latter procedure. One-step incubation is not only time-saving but seems to be also more sensitive with regard to the detection limit. However, care must be taken to circumvent the hook-effect occurring at high virus concentrations.     

Linkage analysis of the Duffy blood group marker with several chromosome 1 genes in an extended pedigree with Charcot-Marie-Tooth disease

Summary We have recently demonstrated tight linkage of the Duffy blood group marker to the -spectrin gene in an extended pedigree with Charcot-Marie-Tooth neuropathy. To determine a more precise location of the Duffy blood group locus on the chromosome 1 map we have tested several more chromosome 1 genes for linkage with this marker. We found suggestive linkage with the antithrombin III and apolipoprotein A2 genes and conclusive linkage with the gene coding for -nerve growth factor.     

Excision and transposition of two Ds transposons from the bronze mutable 4 derivative 6856 allele of Zea mays L

Summary The regulatory mutation bronze mutable 4 Derivative 6856 (bz-m4 D6856) contains a complex 6.7 kb Dissociation (Ds) element tagged with a duplication of low copy bz 3 flanking sequences (Klein et al. 1988). This creates a unique opportunity to study the transposition of a single member of the repetitive family of Ds elements. Eighteen full purple revertants (Bz alleles) of bz-m4 were characterized enzymatically and by genomic mapping. For 17 of the Bz alleles, reversion to a wild-type phenotype was caused by excision of the 6.7 kb Ds transposon. Nine of these Bz alleles retained the transposon somewhere in their genome. In this study we show that like Ac (Schwartz 1989; Dooner and Belachew 1989), the 6.7 kb Ds element can transpose within a short physical distance, both proximal and distal to its original position. Additional bz sequences have been mapped immediately distal to the mutant locus in bz-m4 D6856; genetic evidence suggests these are flanked by two additional Ds elements. The remaining Bz revertant, Bz :107, arose from excision of a more complex 13 kb Ds element.     

A Simple and Widely Applicable Method for Preparing Homogeneous and Stable Quality Control Samples in Water Microbiology

Test strains suspended in skim milk, quickly frozen in dry ice-ethanol, and stored at - 70°C can be used as quality control samples that are immediately available by quickly thawing at 37°C. The samples remain homogeneous and stable for at least 1 year, except for Aeromonas hydrophila, which decreases 20 to 30% in 1 year.     

Determination of cisplatin and cis-diammineaquachloroplatinum(II) ion by liquid chromatography using post-column derivatization with diethyldithiocarbamate

A post-column derivatization method has been developed for the determination of cisplatin and its monohydrated form. Cisplatin was isolated on a strong anion-exchange column, while a strong cation-exchange column was used for the monohydrated complex. Diethyldithiocarbamate was used as reagent and the influence of temperature, pH and methanol content on the yield of derivative was investigated. The reaction was quantitative using a packed-bed reactor with a surrounding temperature of 115°C and a mobile phase consisting of 0.125 M succinic acid—sodium hydroxide buffer pH 5.2 and methanol (2:3, v/v). The resulting complex, Pt(DDTC)₂, was monitored photometrically at 344 nm. The precision of the determination was 11.5% (C.V.) at an injected amount of 20 ng (n = 12) for monoaqua and 8.0% (C.V.) at 9 ng (n = 10) for cisplatin. The method was used to evaluate the plasma concentration of cisplatin and its monohydrated form in a patient.