Phage-induced fucosidases hydrolysing the exopolysaccharide of Klebsiella aerogenes type 54[A3(S1)]

Several strains of bacteriophage have been isolated that induce the formation of a polysaccharide hydrolase after infection of Klebsiella aerogenes type 54 [A3(S1)]. The action of this enzyme on polysaccharide solutions was to decrease their viscosity and increase their reducing value. These effects were associated with the release of two oligosaccharides (O1 and O2) from the polysaccharide. These two substances are not identical with any of the four oligosaccharides isolated from autohydrolysates. The two enzymically isolated fractions have been tentatively identified as tetrasaccharides, and oligosaccharide O2 is probably an acetylated version of oligosaccharide O1. This latter oligosaccharide differs in some way, still unknown, from the tetrasaccharide cellobiosylglucuronosylfucose found in acid hydrolysates of the slime polysaccharide. The enzyme is limited in its activity to the polysaccharide excreted by the A3 strain of K. aerogenes type 54 or by similar strains. It is also active on the polysaccharides altered by acid or alkaline treatment. The enzyme has optimum activity at pH6.5. A study of the products released by enzyme action has shown it to be a fucosidase splitting the fucosylglucose linkages found in the intact polysaccharide.     

Genetic and physical mapping of a novel region close to the fragile X site on the human X chromosome

We report the isolation and characterization of a novel DNA marker (1A1) in Xqter in the region of the fragile X. Genetic studies in families segregating for the fragile X syndrome suggest that 1A1 lies between the disease mutation and the distal locus, DXS52. Studies in normal and fragile X families show that 1A1 is tightly linked to DXS52 (Zmax = 17.20; theta max = 0.03) and F8 (Zmax = 7.01; theta max = 0.08). Multipoint mapping of families supports the order Xcen-DXS105-FRAXA-1A1-DXS52-(F8, DXS115)-Xqter. Pulsed-field gel electrophoresis (PFGE) studies demonstrate that 1A1 defines a new region of at least 2 Mb of DNA not physically linked to DXS52 or F8, thus extending the physical map of Xq27-qter to over 4 Mb. Complex partial digestion PFGE patterns, probably due to differing degrees of methylation, are observed with 1A1 in unrelated normal and fragile-X-positive individuals, whereas other distal markers give uniform digestion profiles. Physical data suggest that 1A1 lies in a region less CpG rich than other distal markers in Xq27-qter.     

The Development of Infection Structures of Sderotium cepivorum on Onion

Growth of Sderotium cepivorum mycelium on root tissue differed from that on stem tissue. Hyphae grew along the lines of the longitudinal epidermal cell walls often producing side branches which resulted in a distinctive pattern of growth. Penetration occurred mainly between anticlinal wall junctions with occasional direct penetration through the periclinal wall. Growth on the surface of the stem resulted in the formatíon of donne shaped infection cushions, arising from repeated dichotomous branching of hyphal tips. Penetration of the stem tissue occurred solely from these structures. The results of experiments using artificial membranes and surface replicas indicated that the stimulus for attempted penetration was chemical in nature but that the nature of the infection structure produced was determined by the relative strength of the tissue under attack.     

Adenylate cyclase toxin from Bordetella pertussis. Identification and purification of the holotoxin molecule

Bordetella pertussis adenylate cyclase (AC) toxin is a calmodulin-activated adenylate cyclase enzyme which has the capacity to enter eukaryotic target cells and catalyze the conversion of endogenous ATP into cyclic AMP. In this work, the AC holotoxin molecule is identified and isolated. It is a single polypeptide of apparent 216 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Monoclonal antibodies which immunoprecipitate AC activity from extracts of wild type B. pertussis (BP338) react with this 216-kDa band on Western blots, and it is absent from a transposon Tn5 mutant (BP348) specifically lacking AC toxin. Isolation of the 216-kDa protein to greater than 85% purity by hydrophobic chromatography, preparative sucrose gradient centrifugation, and affinity chromatography using either calmodulin-Sepharose or monoclonal antibody coupled to Sepharose 4B yields stepwise increases in AC toxin potency, to a maximum of 88.3 mumol of cAMP/mg of target cell protein/mg of toxin. Electroelution of the 216-kDa band following sodium dodecyl sulfate-polyacrylamide gel electrophoresis yields a preparation with both AC enzyme and toxin activities. These data indicate that this protein represents the AC holotoxin molecule.     

Fragile-X syndrome: Unique genetics of the heritable unstable element

The fragile site at Xq27.3 is an unstable microsatellite repeat, p(CCG)n. In fragile-X syndrome pedigrees, this sequence exhibits variable amplification, the length of which correlates with fragile-site expression. There is a direct relationship between increased p(CCG)n copy number and propensity for instability: individuals having large amplifications exhibit somatic variation due to increased instability. The instability of the p(CCG)n repeat, when transmitted through affected pedigrees, explains the unusual segregation patterns of fragile-X phenotype, referred to as the Sherman paradox. All individuals of fragile-X genotype were found (where testing was possible) to have a parent with amplified p(CCG)n repeat, indicating that few, if any, cases of fragile-X syndrome are not familial.     

Isolation of high-molecular-weight plant DNA for DNA damage quantitation: relative effects of solar 297 nm UVB and 365 nm radiation

Quantitation of UV-induced DNA damages in nanogram quantities of non-radiactive DNA from irradiated plants by gel electrophoresis requires a prompt, efficient, high-yield method of isolating DNA yielding high-molecular-weight, enzymatically digestible DNA. To meet these criteria we devised a high-yield method for isolating from plant tissue, DNA whose single-strand molecular length is greater than about 170 kb. Leaf tissue is embedded in agarose plugs, digested with Proteinase K in the presence of detergent, and treated with phenylmethylsulfonyl fluoride (PMSF). The agarose plugs are then soaked with buffer appropriate to the desired enzyme treatment. Evaluation of the DNA on neutral and alkaline gels indicates its high molecular length and low frequency of single-strand breaks. The DNA can be digested with damage-specific and other endonucleases. The method is especially suitable for DNA damage quantitation, as tissue processing is carried out immediately after harvesting (allowing DNA lesion measurement at precisely known times after irradiation), and many samples can be easily handled at once. It should also be useful for molecular analysis of large numbers of plant samples available only in small quantities. We here use this method to quantitate DNA damage induced by 297 and 365 nm radiation, and calculate the relative damaging effects of these wavebands in today's solar spectrum.