Plasmids and Bacteriocins in Caulobacter Species

A survey of wild-type Caulobacter strains revealed naturally occurring plasmids in three species. Further analysis showed instances of naturally occurring antibiotic resistance and bacteriocin production.     

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.     

Glycosyl acceptors in intact and permeabilized normal and cystic fibrosis fibroblasts

Using cell permeabilization, a technique which allows addition of exogenously supplied radiolabeled sugar nucleotides to serve as direct glycosyl donors, oligosaccharide biosynthesis was examined in fibroblasts obtained from normal and cystic fibrosis (CF) subjects. Incubation of logarithmically growing cells with either radiolabeled leucine or xylose has indicated that there was a difference in the synthetic rate between the cell types. Protein synthesis in normal cells made permeable with 50 m?g/ml lysolecithin (LL) was demonstrated to be absent, and could not be induced to take place by adding exogenous components, including energy sources and amino acids, normally required for protein synthesis. Thus radiolabeled sugars were being added to peptide acceptors which were already present at the time of LL addition. Both permeable and intact fibroblasts were exposed to labeled UDP-xylose, UDP-galactose, and UDP-glucuronic acid, all donors of mucopolysaccharide precursors. The uptake of xylose into protein was the same for both normal and CF cells, but permeable CF fibroblasts incorporated statistically greater amounts of sugar from UDP-galactose and UDP-glucuronic acid. Intact CF cells were also labeled using these two sugar nucleotides. Trypan blue exclusion indicated CF and normal fibroblasts were equally intact. This and the fact that preincubation of CF cells with the appropriate cold sugar nucleotide eliminated the differences in incorporation between the normal and CF cells suggested that CF fibroblasts had more cell surface acceptor than the normal cells.     

Extrachromosomal Elements in Group N Streptococci

The deoxyribonucleic acid (DNA) of Streptococcus lactis C2, S. cremoris B(1), and S. diacetilactis 18-16 was labeled by growing cells in Trypticase soy broth containing (3)H-labeled thymine. The cells were gently lysed with lysozyme, ethylenediaminetetraacetic acid, and sodium lauryl sulfate. The chromosomal DNA was separated from plasmid DNA by precipitation with 1.0 M sodium chloride. The existence of covalently closed circular DNA in the three organisms was shown by cesium chloride-ethidium bromide equilibrium density gradient centrifugation of the cleared lysate material. In an attempt to correlate the loss of lactose metabolism with the loss of plasmid DNA, lactose-negative mutants of these organisms were examined for the presence of extrachromosomal particles. Covalently closed circular DNA was detected in the lactose-negative mutants of S. lactis C2 and S. diacetilactis 18-16. In S. cremoris B(1), however, no covalently closed circular DNA was observed by using cesium chloride-ethidium bromide gradients. Electron micrographs of the satellite band material from S. lactis C2 and its lactose-negative mutant confirmed the presence of plasmid DNA. Three distinct plasmids having approximate molecular weights of 1.3 x 10(6), 2.1 x 10(6), and 5.1 x 10(6) were observed in both organisms.     

Isolation and Purification of Prodigiosin from Vibrio psychroerythrus

The red pigment of Vibrio psychroerythrus (formerly marine psychrophile NRC 1004) was identified as prodigiosin by comparison of its mass spectrum, absorption spectrum in the visible range, and chromatographic behavior with prodigiosin isolated from Serratia marcescens. The properties of the V. psychroerythrus pigment were clearly distinguishable from five other prodigiosin-like compounds isolated from three different microorganisms.     

Differentiation studies on separated rabbit early erythroid cells

Haemoglobin-containing cells were removed from cell suspensions of adult rabbit bone marrow by immune lysis, and the remaining cells were layered into BSA density gradients. The top fractions contained early erythroid cells, while fractions near the bottom of the gradient contained granulocytes. Two populations of erythroid cells from anaemic rabbits were resolved by the gradient which differed in their time of maximum stimulation of haem synthesis, in culture with erythropoietin. In addition, a difference in requirement for the presence of erythropoietin in the culture medium was found in separated erythroid cells from rabbits with varying degrees of anaemia.