Microbial Activities in Undecompressed and Decompressed Deep-Seawater Samples

Microbial transformations of ¹⁴C-labeled substrates (sodium glutamate, Casamino Acids, glucose, and sodium acetate) were measured in undecompressed seawater samples collected from depths of 1,800 to 6,000 m, during 14- to 21-day incubation periods at in situ temperature (3°C). Each substrate was tested at two concentrations (ca. 0.5 and 5.0 μg/ml) and two in situ pressures. The data were compared to 1-atmosphere (ca. 1.013 × 10² kPa) controls. The rates of ¹⁴C incorporation and ¹⁴CO₂ production as well as the amounts of total substrate utilization were generally lower at pressure than in the decompressed controls but were significantly different for each of the four substrates used. The utilization of acetate was the least affected by pressure; rates were similar to those measured at 1 atmosphere in two out of four experiments. In contrast, transformation rates of the amino acids at pressure averaged to only 38% of those in the controls. A single but reproducible “barophilic” response was observed with glucose as a substrate in samples collected from a depth of 4,500 m at a specific area in the northwestern Atlantic Ocean. Except for this latter set of experiments, the transformation of all substrates showed an increased lag period at pressure as compared to the 1-atmosphere controls.     

Enterotoxin production in milk at 22 and 4 degrees C by Escherichia coli and Yersinia enterocolitica.

Enterotoxigenic Escherichia coli (five strains) and Yersinia enterocolitica (five strains) were cultivated in sterile milk at 22 and 4 degrees C. The bacteria grew well at both temperatures. Three strains of E. coli produced heat-labile enterotoxin in the milk at 22 degrees C as demonstrated by enzyme-linked immunosorbent assay. Heat-stable enterotoxins were not detected in milk by the infant mouse test.     

Phase separation in dipalmitoyl phosphatidylcholine bilayers induced by ionophores and binary electrolytes

Thermotropic behavior of unsonicated aqueous dispersion of dipalmitoyl phosphatidylcholine (DPPC) has been studied by scanning microcalorimetry and fluorescent probe method. Phase separation in the lipid bilayers was observed for systems containing ionophores (valinomycin, dinactin) and 1 : 1 electrolytes (NaCl, KCl, RbCl, CsCl). The ratio of lipid phases coexisting in the systems appeared to be dependent on the concentration of the electrolytes. Changes in the thermotropic properties of the lipid phase induced by valinomycin were observed when K+ and Rb+ ions-forming complexes with the ionophore were present in the systems. The latter phenomenon was not found for the systems containing dinactin possessing a lower ability for complex formation with the cations.     

Stability of glucose oxidase and catalase adsorbed on variously activated 13X zeolite

The use of 13X zeolite (0.1-0.4-mm granules), treated with 2N and 0.01N HCI, 0.01M citric acid, 0.1M citric-phosphate buffer (pH 3.6), and in untreated form to adsorb glucose oxidase of fungal origin and microbial catalase was examined. Physicochemical analysis of the support demonstrated that its crystalline structure, greatly altered by the HCl and buffer, could be partially maintained with citric acid. The specific adsorption of the enzymes increased with decreasing pH and proved to be considerable for all the supports. The stability with storage at 25 degrees C is strictly correlated with the titrable acidity of the activated zeolite expressed as meq NaOH/g and with pH value of the activation solution. It proved to be lower than 55 h for both enzymes if adsorbed on zeolite treated with 2N HCl, and 15-fold and 30-fold higher for glucose oxidase and catalase adsorbed, respectively, on zeolite treated with the 0.1M citric-phosphate buffer and 0.01M citric acid. The specific adsorption of glucose oxidase and catalase was, respectively, 1840 U/g at pH 3.0 and 6910 U/g at pH 5.0. Their half-life at 25 degrees C with storage at pH 3.5 for the former and at pH 5.0 for the latter was 800 and 1560 h vs. 40 and 110 h for the corresponding free enzymes.     

Maximum likelihood estimation of growth yields

This work is concerned with statistical methods to estimate yield and maintenance parameters associated with microbial growth. For a given dilution rate, an experimenter typically measures substrate concentration, oxygen utilization rate, the rate of carbon dioxide evolution, and biomass concentration. These correlated response variables each contain information about the maintenance and yield parameters of interest. A maximum likelihood estimator which combines this correlated information for the yield and maintenance parameters is proposed, evaluated, and tested on literature data. Both point and interval estimators are considered.     

Secretion of trans-zeatin by Agrobacterium tumefaciens: A function determined by the nopaline Ti plasmid

Production of the plant cytokinin, trans-zeatin, by a number of strains of Agrobacterium tumefaciens was measured by a combination of traceenrichment, HPLC and radioimmunoassay and confirmed by mass spectrometry. Secretion of trans-zeatin into a culture medium is a constitutive function of those strains which harbor a nopaline Ti plasmid. Strains cured of the nopaline Ti plasmid and those which harbor octopine or agropine plasmids are non-producers. Reacquisition of nopaline plasmids by cured strains restores production.     

Safety evaluation of nuclear polyhedrosis virus replication in pigs

To evaluate the hygienic risk involved in using baculoviruses for insect pest control, safety studies are required. Pigs were chosen as representative test animals of commercial and agricultural importance. The tests were aimed at detecting virus propagation, immune reactions, and signs of acute infection (changes in body temperature and hematology profile, swelling of lymph nodes). Four of five animals inoculated with nuclear polyhedrosis virus showed a slight temperature rise at day 2 postinfection. After day 4 postinfection, no differences between infected animals and controls were observed. In the bioassay, virus activity could be recovered from fecal samples; however, no activity was found in organ extracts. The data did not indicate hygienic risks involved in the application of nuclear polyhedrosis virus, especially that from Mamestra brassicae, in biological pest control.     

Amino acid sequence in the reactive site region of an acid-stable inhibitor of trypsin, chymotrypsin and intracellular proteinases from rabbit serum

The thermo- and acid-stable trypsin, chymotrypsin and intracellular proteinases inhibitor (TAS-inhibitor) from rabbit serum was digested by trypsin, and its domain (Mr 6200) with antitryptic activity was obtained in homogeneous state. The N-terminal amino acid sequence of this domain was established by automatic Edman degradation: Thr-Val-Ala-Ala-Cys-Asx-Leu-Pro-Ile-Val-Pro-Gly-Pro-X-Arg-Gly-Ile-Phe-X- Leu-X-Ala-Phe-X-Ala-Val-X-Gly. A high degree of homology of the primary structures rabbit, human and bovine TAS-inhibitors was demonstrated.