Restriction enzyme maps of the chimeric R/Ent plasmid pCG86 and the related Ent plasmid P307

Complete restriction enzyme cleavage site maps for three enzymes and incomplete maps for four enzymes have been constructed for the chimeric R/Ent plasmid pCG86 of Escherichia coli and the related Ent plasmid P307.     

Change of plasmid DNA structure, hypermethylation, and Lon-proteolysis as steps in a replicative cascade.

I have defined conditions under which RepFIC plasmid DNA can be maintained in a state of lowered helical density. In exponentially growing cultures, the DNA of lowered helical density is present in small amounts but never totally absent, suggesting that it is a normal variant of plasmid maintenance. It is fully methylated at frequent sites by dam-methyltransferase, some not previously recognized, further suggesting that the variant is a precursor of replication. The low-helical density plasmid is present in dam hosts, indicating that methylation is not essential for the change in helical density. The lowered helical density is stabilized in lon hosts, suggesting that Lon-protease may remove both the protein(s) that lower the helical density and the dam-methyltransferase after each round of replication.     

Triuridopsis,a new monotypic genus inTriuridaceae

The new monotypic genusTriuridopsis from Peru is described. A key to the genera ofTriuridaceae worldwide is given.     

G.L.C.-M.S. of N-(1-deoxyalditol-1-yl)octadecylamine derivatives in the analysis of methanolysates of neoglycolipids obtained by reductive amination

Hydrophobic conjugates of a series of aldoses have been prepared by reductive amination with octadecylamine and sodium cyanoborohydride, as model compounds for the analysis of reductively aminated oligosaccharides derived from capsular polysaccharides of Streptococcus pneumoniae. In the context of the methanolysis procedure for sugar analysis, g.l.c. and g.l.c.-m.s. (e.i.-mode) studies were carried out on the N-(1-deoxyalditol-1-yl)octadecylamine derivatives obtained after treatment with methanolic HCl, and subsequent N-acetylation and trimethylsilylation.     

Cellobiose uptake by the cellulolytic ruminal anaerobe Fibrobacter (Bacteroides) succinogenes

Cellobiose transport by the cellulolytic ruminal anaerobe Fibrobacter (Bacteroides) succinogenes was measured using randomly tritiated cellobiose. When assayed at the same concentration (1 mM), total cellobiose uptake was one-fourth to one-third that of total glucose uptake. The abilities of F. succinogenes to transport cellobiose or glucose were not affected by the sugar on which the cells were grown. Aspects of the simultaneous transport of [14C(U)]glucose and [3H(G)]cellobiose, the failure of high concentrations of cold glucose to compete with hypothetical [3H(G)]glucose (derived externally from [3H(G)]cellobiose), and differential metal-ion stimulation of cellobiose transport indicate a cellobiose permease, rather than cellobiase plus glucose permease, was responsible for cellobiose transport. Glucose (10-fold molar excess) partially inhibited cellobiose transport. This was enhanced by prior incubation of the cells with glucose, suggesting subsequent metabolism of the glucose was responsible for the inhibition. Compounds interfering with electron transport or maintenance of transmembrane ion gradients inhibited cellobiose uptake, indicating that active transport rather than a phosphoenolpyruvate:phosphotransferase system catalyzed cellobiose transport. Na+, but not Li+, stimulated cellobiose transport.