Growth and survival of Bordetella bronchiseptica in natural waters and in buffered saline without added nutrients

Bordetella bronchiseptica showed increases in viable count when incubated in phosphate-buffered saline (PBS), in reagent-grade water, and in local lake and pond waters, all without added nutrients. Within 48 to 72 h at 37 degrees C in PBS and in lake and pond waters, stationary-phase populations of around 2.7 x 10(6) CFU/ml developed from washed B. bronchiseptica inocula of around 2 x 10(3) CFU/ml. Increases in CFU on the order of five- and eightfold, respectively, were observed in reagent-grade water and in seawater from the same sizes of inocula. The organisms remained viable for at least 3 weeks in PBS and in lake waters at 37 degrees C. The possibility that carry-over of nutrients was responsible for growth was discounted by showing serial transfer of B. bronchiseptica in PBS under conditions in which Escherichia coli tested in parallel rapidly died out.     

International scientific meetings: relation between structure and function.

Increasing pressure is being placed on the scientific community to evaluate research activities. Scientific meetings consume a small but important fraction of the research budget. Audit of a well established series of scientific meetings showed that they met their immediate objectives in that they were international and multidisciplinary and provided a forum in which all participants actively contributed to discussion. The meetings had a positive outcome for the participants, leading in many cases to the subsequent exchange of research material (60% of participants) and to the establishment of collaborative research projects (31%). The impact of the meetings on the scientific community at large was assessed by citation analysis, which showed that the proceedings were cited early, often, and over a substantial period.     

Fatty acid synthetase, malic enzyme and other NADP+ binding dehydrogenases have similar antigenic determinant(s) at the NADPH binding domain

The sequence of tryptic and chymotryptic peptides from cytosolic and mitochondrial rabbit liver serine hydroxymethyltransferase are compared to the proposed sequence of a protein coded for by the glyA gene of Escherichia coli. The E. coli glyA gene is believed to code for serine hydroxymethyltransferase. Extensive sequence homology between these peptides were found for the proposed E. coli enzyme in the aminoterminal two-thirds of the molecule. All three proteins have identical sequences from residue 222-231. This sequence is known to contain the lysyl residue which forms a Schiff's base with pyridoxal-P in the two rabbit liver enzymes. These results support the interpretation that the proposed sequence of E. coli serine hydroxymethyltransferase is correct. The data also show that cytosolic and mitochondrial serine hydroxymethyltransferase are homologous proteins.     

The biochemical and ultrastructural effects of tunicamycin and D-glucosamine in L1210 leukemic cells

Tunicamycin was found to specifically inhibit the incorporation of a number of sugars into L1210 leukemia cell glycoproteins. This inhibition of glyco-protein biosynthesis led to a cessation of cell growth which was reversible in a dose-dependent and time-dependent manner. After removal of the antibiotic from L1210 cell cultures resumption of sugar incorporation preceded that of thymidine incorporation and the recovery of cell growth. The treatment of cells with tunicamycin resulted in a significant increase in the intracellular pool of UDP-N-acetylglucosamine which occurred concurrently with alterations in cell ultrastructure including distentions of the endoplasmic reticulum and nuclear membranes. Similar ultrastructural changes and increases in the intracellular pools of UDP-sugars were observed in L1210 cells exposed to 5 mM D-glucosamine, which suggested that the antiproliferative effects of tunicamycin may be related to the accumulation in the endoplasmic reticulum of one or more nucleotide sugar precursors of asparagine-linked glycoprotein biosynthesis. However, the biological effects of tunicamycin could be distinguished from those caused by D-glucosamine. Exposure of L1210 cells to tunicamycin resulted in specific alterations in the biochemical composition of the plasma membrane and in the inhibition of cellular agglutination by wheat germ agglutinin which were not apparent following exposure to equitoxic concentrations of the aminosugar. These studies, together with those which demonstrated that recovery of the cellular capacity to synthesize glycoproteins was obligatory for the recovery of cellular proliferation in tunicamycin-treated cells, suggested that inhibition of the synthesis of glycoproteins was the major factor limiting L1210 leukemic cell proliferation.     

Number of Transformable Units Per Cell in Diplococcus pneumoniae

Analysis of frequencies of single and random multiple transformations in Diplococcus pneumoniae showed that there are at least two transformable units per cell of the total population in highly competent cultures. If 100% of the cells are competent in these cases, the units may be interpreted as the strands of one duplex deoxyribonucleic acid recipient chromosome. The theory is developed to allow for extension to more complex situations.     

Specificity studies of 3-mercaptopyruvate sulfurtransferase

3-Mercaptopyruvate sulfurtransferase (E.C. 2.8.1.2; MST) is an enzyme believed to function in the endogenous cyanide (CN) detoxification system because it is capable of transferring sulfur from 3-mercaptopyruvate (3-MP) to CN, forming the less toxic thiocyanate (SCN). To date, 3-MP is the only known sulfur-donor substrate for MST. In an effort to increase the understanding of what chemical properties of 3-MP affect its utilization as a substrate, in vitro enzyme kinetic studies of MST were conducted using two mercaptic acids that are structurally related to 3-MP. Neither of these compounds was able to serve as a sulfur-donor substrate for MST. Inhibitor studies determined that 3-mercaptopropionic acid did not affect the K_m of MST for 3-MP but did decrease V_max and, thus, was determined to be a noncompetitive inhibitor. Alternatively, 2-mercaptopropionic acid 2-MPA decreased K_m and V_max and was determined to be an uncompetitive inhibitor of MST with respect to 3-MP. These data indicate that the α-keto group of 3-MP is necessary for its utilization as a substrate, and the inhibitor studies suggest that the position of the sulfur may also affect the binding of these compounds to the enzyme. These observations increase the understanding of what factors can affect the utilization of a compound as a sulfur-donor substrate for MST and may aid in the development of alternative sulfur-donor substrates for MST. © 1996 John Wiley & Sons, Inc.