Transport of Ca2+ by Yersinia pestis.

Low-calcium-response, or Lcr, plasmids of yersiniae are known to promote an in vitro nutritional requirement for 2.5 mM Ca2+ at 37 degrees C which, if not fulfilled, results in cessation of growth with induction of virulence functions (Lcr+). The mechanism whereby Ca2+ regulates this metabolic shift is unknown. Radioactive Ca2+ was not actively accumulated by yersiniae but was excluded by an exit reaction analogous to those described for other bacteria. Nevertheless, cultivation at 37 degrees C with 0.1 mM Ca2+, a level insufficient to prevent restriction of cell division, promoted significantly more binding of the cation by Lcr+ organisms than by plasmid-deficient Lcr- mutants. According, Lcr+ yersiniae may possess unique ligands capable of recognizing Ca2+.     

Electrophoretic and immunochemical study of the lipopolysaccharides produced by chemostat-grown Escherichia coli O157

Two chemically different O-polysaccharides, a low molecular mass form of LPS and core LPS produced by chemostat-grown E. coli O157, were analysed by SDS-PAGE, silver staining and immunoblotting. The reactivities of the different O-polysaccharides with antisera prepared against E. coli O157 grown in batch culture, Salmonella O30 or Brucella abortus were very similar, showing that the O-polysaccharides share at least some antigenic determinants. The reactions of the low molecular mass LPS with the antisera indicated it was semi-rough LPS having one repeat unit of the O-polysaccharide attached to core LPS.     

Kinetics and specificity of T and B cell responses in relapsing experimental allergic encephalomyelitis

T and B cell responses to myelin basic protein (MBP) and its relevant peptide fragments were examined throughout the course of MBP-induced relapsing experimental allergic encephalomyelitis (REAE) in (SJL X PL)F1 mice. T cell reactivity, measured by the antigen-driven proliferation of lymph node T cells in vitro, was directed predominantly against the encephalitogenic MBP-P2 peptide (amino acids 1 to 37) at all stages of disease. Levels of responsiveness did not correlate with disease expression, but declined over time to a relapse level that was four- to sixfold lower than that observed during peak acute stage reactivity. Relapse responses were further distinguished by the detection of host I-E restrictions on Lyt-1+ T cell recognition of P2, P2 recognition by acute-stage T cells occurring solely in the context of host I-A molecules. These data imply an increase in the heterogeneity of relapse T cell responses to MBP to include clones restricted by additional class II glycoproteins. A role for additional CNS autoantigens in the stimulation of relapse T cells is also considered. Serum antibody responses to MBP or the P2 fragment fluctuated randomly throughout R-EAE when total antibody activity (IgM plus IgG) was measured. However, analysis of individual isotypes of IgG immunoglobulins revealed an apparent correlation between peak antigen-binding activity and disease expression which may reflect either an effector or regulatory role for humoral immunity in recurrent EAE. Patterns of early antibody reactivity also distinguished F1 mice that developed or failed to develop disease signs after immunization, the latter exhibiting a consistent drop in antigen-binding activity 4 to 5 days before the usual onset of acute-stage paralysis. The results are considered with regard to possible mechanisms of chronic disease regulation in an environment of functional T cell suppression.     

Structural analysis of the pilE region of Neisseria gonorrhoeae P9

We have determined the nucleotide sequence of an expressed structural pilus gene (pilE) derived from Neisseria gonorrhoeae strain P9-2. Detailed analysis of nucleotide sequences upstream from pilE revealed a silent, truncated pilin gene segment that was linked to families of DNA elements (RS1 and RS3) that have previously been identified at the major silent pilin gene locus (pilS1) and at pilE of the independently isolated N. gonorrhoeae strain MS11ms. A nucleotide sequence downstream from pilE was reminiscent of the recognition sequences of several recombinases, including Tn3 tnpR product (resolvase), suggesting a possible role for site-specific events in the recombinational modulation of pilus expression.     

Sterol conjugates of two phenotypically different calli of Beta vulgaris

Steryl glycosides are the predominant form of sterol at 88% of the total sterol in non-betalain producing calli of Beta vulgaris. The total sterol decreases and sterol form shifts from steryl glycosides to 97% free sterol upon the transition of non-betalain to betalain producing calli. A substantial decrease in stigmasterol (24--ethylcholesta-5,22E-dien-3-ol) and sitosterol (24-ethylcholest-5-en-3-ol) levels is observed during this transition, and alters the ratio of ⁷:⁵ sterols. Spinasterol (24- ethyl-5-cholesta-7,22E-dien-3-ol) is the dominant sterol at 43% and 95% of the total sterol in non-betalain producing and betalain producing calli. The level of 22-dihydrospinasterol (24-ethyl-5-cholest-7-en-3-ol) is reduced in both calli to 3% from 25% in leaves. Lanosterol (4,4,14-trimethyl-cholesta-8(9),24-dien-3-ol) and cycloartenol (9,19-cyclopropyl-4,4,14-trimethyl-cholest-24-en-3-ol) were identified in betalain and nonbetalain producing callus respectively.     

Structural studies of the capsular polysaccharide from Haemophilus pleuropneumoniae serotype 2

The capsular polysaccharide of Haemophilus pleuropneumoniae serotype 2 (ATCC 27089) is composed of D-glucose (two parts), D-galactose (one part), glycerol (one part), and phosphate (one part). Hydrolysis, dephosphorylation, methylation, enzymic studies, and 1H and 13C nuclear magnetic resonance experiments showed that the polysaccharide is a high molecular weight polymer of a tetrasaccharide repeating units, linked by monophosphate diester and having the following structure: (Formula: see text).     

Structural elucidation of the Brucella melitensis M antigen by high-resolution NMR at 500 MHz

The Brucella M antigen from the species type strain Brucella melitensis 16M has been identified as a component of the cell wall lipopolysaccharide (LPS). O polysaccharide liberated from this LPS by mild acid hydrolysis exhibited M activity in serological tests and was shown to be a homopolymer of 4-formamido-4,6-dideoxy-alpha-D-mannopyranosyl residues arranged in an oligosaccharide repeating unit as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the native lipopolysaccharide. Structural analysis of the O polysaccharide by NMR methods was difficult due to apparent microheterogeneity of the repeating unit, which was in fact caused by the presence of rotational isomers of the N-formyl moiety. This problem was resolved by chemical modification of the polysaccharide to its amino and N-acetyl derivatives, the 500-MHz 1H and 125-MHz 13C NMR spectra of which could be analyzed in terms of a unique structure through application of pH-dependent beta-shifts and two-dimensional techniques that included COSY, relayed COSY, and NOESY experiments together with heteronuclear C/H shift correlation spectroscopy. On the basis of these experiments and supported by methylation and periodate oxidation data, the structure of the M polysaccharide was determined as a linear polymer of unbranched pentasaccharide repeating units consisting of four 1,2-linked and one 1,3-linked 4,6-dideoxy-4-formamido-alpha-D-mannopyranosyl residues. The marked structural similarity of the M antigen and the A antigen, which is known to be a 1,2-linked homopolysaccharide of 4,6-dideoxy-4-formamido-alpha-D-mannopyranosyl units, accounts for cross-serological reactions of the two and the long-standing confusion surrounding the nature of their antigenic determinants. Structural and serological considerations in conjuction with the sodium dodecyl sulfate banding pattern of Brucella A LPS suggest that its biosynthesis differs appreciably from that of the M antigen, which appears to be synthesized by regulated assembly of preformed oligosaccharide repeating units. Temperature, lysogenic phage may be responsible for such biosynthetic and structural variations.     

Actinomycetes inducing phytotoxic or fungistatic activity in a Douglas-fir Forest and in an adjacent area of repeated regeneration failure in Southwestern Oregon

Actinomycetes were isolated from the upper 1 - 3 cm of the soil layer in a well-developed forest and in an adjacent clearcut area where Douglas-fir [Pseudotsuga menziesii (MIRB.) Franco] regeneration had been impaired for two decades. The population density in the clearcut area was two times as high as that in the forested area. The percentage of actinomycetes that inhibited seed germination of the test plants was significantly higher in isolates obtained from the clearcut area than in those obtained from the forested area, and isolates from the clearcut showed five times the phytotoxic effect of those from the forest. Some actinomycete isolates, 4 % from the clearcut and 2.6 % from the forest, significantly reduced in vitro growth of two common ectomycorrhizal fungi of Douglas-fir,Laccaria laccata andHebeloma ovstuliniforme. Two actinomycete isolates from the clearcut reduced fungal growth by 40 % and 73 %. Reduction of the nutrient in the growth medium did not affect the antifungal activity of the actinomycetes. The data support the idea that, along with other factors, phytotoxic and antifungal actinomycetes may suppress natural regeneration or establishment of planted seedlings - either directly or. indirectly - through inhibition of seed germination or of mycorrhizal fungi.