Analogue inhibitor of 2-5A action: effect on the interferon-mediated inhibition of encephalomyocarditis virus replication.

Chemically synthesised CH3Sp(A2'p)2A2'pp3'OCH3 has been used to assess the importance of the ppp(A2'p)nA (n greater than or equal to 2: 2-5A) system in the antiviral action of interferon against encephalomyocarditis virus (EMC). It inhibits activation of the 2-5A-dependent RNase by 2-5A in intact mouse L929 cells and cell-free systems. In interferon-treated, EMC-infected L929 cells it inhibits 2-5A-mediated rRNA cleavage and partially restores EMC RNA synthesis and virus yield. Activation of the 2-5A-dependent RNase must, therefore, play some part in interferon action against the growth of EMC virus in such cells.     

Mobilization of cloned luciferase genes into Vibrio harveyi luminescence mutants

A recombinant plasmid which carried a 5 kb fragment of Vibrio harveyi DNA containing the luxA and luxB genes was mobilized from Escherichia coli into luminescence-deficient mutants of V. harveyi. The cloned genes complemented a temperature sensitive luciferase mutation, but failed to complement lesions in two different aldehyde deficient mutants. Expression of the cloned genes was not subject to autoinduction in either E. coli or in V. harveyi.     

Effects of Metals on Methanogenesis, Sulfate Reduction, Carbon Dioxide Evolution, and Microbial Biomass in Anoxic Salt Marsh Sediments

The effects of several metals on microbial methane, carbon dioxide, and sulfide production and microbial ATP were examined in sediments from Spartina alterniflora communities. Anaerobically homogenized sediments were amended with 1,000 ppm (ratio of weight of metal to dry weight of sediment) of various metals. Time courses in controls were similar for CH₄, H₂S, and CO₂, with short initial lags (0 to 4 h) followed by periods of constant gas production (1 to 2 days) and declining rates thereafter. Comparisons were made between control and experimental assays with respect to initial rates of production (after lag) and overall production. Methane evolution was inhibited both initially and overall by CH₃HgCl, HgS, and NaAsO₂. A period of initial inhibition was followed by a period of overall stimulation with Hg, Pb, Ni, Cd, and Cu, all as chlorides, and with ZnSO₄, K₂CrO₄, and K₂Cr₂O₇. Production of CO₂ was generally less affected by the addition of metals. Inhibition was noted with NaAsO₂, CH₃HgCl, and Na₂MoO₄. Minor stimulation of CO₂ production occurred over the long term with chlorides of Hg, Pb, and Fe. Sulfate reduction was inhibited in the short term by all metals tested and over the long term by all but FeCl₂ and NiCl₂. Microbial biomass was decreased by FeCl₂, K₂Cr₂O₇, ZnSO₄, CdCl₂, and CuCl₂ but remained generally unaffected by PbCl₂, HgCl₂, and NiCl₂. Although the majority of metals produced an immediate inhibition of methanogenesis, for several metals this was only a transient phenomenon followed by an overall stimulation. The initial suppression of methanogenesis may be relieved by precipitation, complexation, or transformation of the metal (possibly by methylation), with the subsequent stimulation resulting from a sustained inhibition of competing organisms (e.g., sulfate-reducing bacteria). For several environmentally significant metals, severe metal pollution may substantially alter the flow of carbon in sediments.     

Cytoplasmic organization in cerebellar dendritic spines

Three sets of filamentous structures were found to be associated with synaptic junctions in slices of cerebellar tissue prepared by rapid- freezing and freeze-etch techniques. The electron-dense fuzz subjacent to postsynaptic membranes corresponds to a web of 4-6-nm-diam filaments that were clearly visualized in rapid-frozen, freeze-etched preparations. Purkinje cell dendritic spines are filled with a meshwork of 5-7-nm filaments that were found to contact the spine membrane everywhere except at the synaptic junction, and extend through the neck of the spine into the parent dendrite. In addition, 8-10-nm microfilaments, possibly actin, were seen to be associated with the postsynaptic web and to extend into the body and neck of the spine. The arrangements and attachments of the filamentous elements in the Purkinje cell dendritic spine may account for its shape.     

Interaction of Pseudomonas Bacteriophage 2 with the Slime Polysaccharide and Lipopolysaccharide of Pseudomonas aeruginosa Strain BI

Purified slime polysaccharide B and lipopolysaccharide of Pseudomonas aeruginosa strain BI were shown to possess receptor-like properties in inactivating Pseudomonas phage 2, whereas lipoprotein and glycopeptide fractions were devoid of activity. On a weight basis, slime polysaccharide B was more effective than lipopolysaccharide in inactivating phage. The specificity of the reaction with slime polysaccharide B was indicated by the fact that slime polysaccharide A of P. aeruginosa strain EI failed to inactivate phage 2. Electron micrographs showed phage 2 in typical, tail-first position of attachment on intact cells of strain BI, slime polysaccharide B, and lipopolysaccharide. Tail fibers were discernible during phage attachment.     

Surfactants as Stimulants of Enzyme Production by Microorganisms

The addition of Tween 80 and sucrose monopalmitate, nonionic surfactants, to fungal cultures resulted in marked increases in yields of the enzymes cellulase, amylase, sucrase, beta-1 --> 3 glucanase, xylanase, purine nucleosidase, and benzoyl esterase. The action appears to be an effect of the surfactant on cell permeability.     

Purine Ribonucleosidase g from Aspergillus foetidus

Nucleosidase g was prepared by growing Aspergillus foetidus on bran, and was purified by passage through a diethylaminoethyl-Sephadex column. The enzyme acted on the purine ribosides (except xanthosine) and on their 5'-phosphates. Action on the latter was a good means for preparing ribose-5-phosphate.     

Survey of the U.S. Gulf Coast for the Presence of Clostridium botulinum

In sediments and animals collected during warm weather months between Key West, Fla., and Brownsville, Tex., Clostridium botulinum, predominantly type E, was demonstrable. Incidence was somewhat higher in the eastern Gulf animals, but the organism was present to the southernmost limits of both Texas and Florida. Types A and F were never detected in warm weather. No bottom type or any single species seemed exclusively vulnerable. In samples collected during colder weather, the east-west incidence differential was minimized in animals but not in sediments, overall incidence was lowered, all known types were present, and type E no longer predominated. Detection by fluorescent-antibody techniques was found to be inadequate.     

Sensitivity of Escherichia coli to proline analogues during osmotic stress and anaerobiosis

L.M. REESE, K.O. CUTLER AND C.E. DEUTCH. 1996. The sensitivity of wild-type Escherichia coli K-12 to a series of proline analogues was determined in cultures containing increasing concentrations of NaCl under both aerobic and anaerobic conditions. The bacteria were most sensitive to L-azetidine-2–carboxylate and L-thiazolidine-4–carboxylate. The minimum inhibitory concentrations for these compounds decreased progressively during osmotic stress, but the bacteria were much more sensitive to these proline analogues under aerobic conditions than during anaerobiosis. The reduced sensitivity under anaerobic conditions did not reflect degradation of the compounds in the culture medium. Since both urine and medullary renal tissue contain relatively low oxygen concentrations, these results raise doubts about the potential use of proline or glycine betaine analogues in treating urinary tract infections.