Phage-induced changes in Vibrio cholerae: serotype and biotype conversions

Phage infection of Vibrio cholerae resulted in antigenic changes. A strain of biotype cholerae serotype Ogawa was converted into serotype Hikojima and gained the ability to synthesize antigenic factor C. Some phage-converted strains remained stable after subculture and were immune to superinfection with the same phage. The stable converted strains were lysogenic and released phage having a host range similar to the phage of the donor strain. Reinfection of unstable converted strains which had "lost" antigen C yielded types able to again synthesize this antigen. The polymyxin resistance character was expressed in the biotype cholerae strain after infection with some phage preparations. These polymyxin-resistant strains possessed three main characteristics of El Tor vibrios. The phage-induced changes described provide V. cholerae with the potential for innumerable genetic combinations.

[Study of the relationship between the trace element content and the physiological properties of Salmonella typhi during submerged cultivation]

The content of trace elements in the cells served as one of the characteristics of physiological condition of the population. The character of the changes in the trace elements content depending on the rate of the microbial multiplication pointed to the importance of the mineral sources of nutrition for the development of the cells analyzed.

Polysaccharide capsule of Escherichia coli: microscope study of its size, structure, and sites of synthesis

This report describes the structure, size, and shape of the uncollapsed polysaccharide capsule of Escherichia coli strain Bi 161/42 [O9:K29(A):H-], its ultrastructural preservation as well as the filamentous components of the isolated capsular material. In a temperature-sensitive mutant, sites were localized at which capsular polysaccharide is "exported" to the cell surface. The highly hydrated capsule of the wild-type cells was visible in the uncollapsed state after freeze-etching, whereas dehydration in greater than or equal to 50% acetone or alcohol caused the capsule to collapse into thick bundles. This was prevented by pretreatment of the cell with capsule-specific immunoglobulin G; the capsule appeared as a homogeneous layer of 250- to 300-nm thickness. The structural preservation depended on the concentration of the anti-capsular immunoglobulin G. Temperature-sensitive mutants, unable to produce capsular antigen at elevated temperatures, showed, 10 to 15 min after shift down to permissive temperature, polysaccharide strands with K29 specificity appearing at the cell surface at roughly 20 sites per cell; concomitantly, capsule-directed antibody started to agglutinate the bacteria. The sites at which the new antigen emerged were found in random distribution over the entire surface of the organism. Spreading of purified polysaccharide was achieved on air-water interfaces; after subsequent shadow casting with heavy metal, filamentous elements were observed with a smallest class of filaments measuring 250 nm in length and 3 to 6 nm in width. At one end these fibers revealed a knoblike structure of about 10-nm diameter. The slimelike polysaccharides from mutants produced filamentous bundles of greater than 100-microns length, with antigenic and phage-receptor properties indistinguishable from those of the wild-type K29 capsule antigen.

Purification, characterization, and immunogenicity of cell-associated glucan from Streptococcus mutans

Appropriate immunization with whole cell vaccines of S mutans appear to induce antibodies that inhibit implantation of S mutans on tooth surfaces and associated dental caries. To better understand the mechanisms by which vaccination prevents S mutans implantation and dental caries, and to prepare antigens whose effectiveness and safety can be tested in animal models of caries, we set out to purify and chemically characterize the CAG of S mutans. The CAG of S mutans strain 6715 was prepared by extracting cells with potasssium hydroxide at 100 C. After neutralization and extensive washing, the water-insoluble product was characterized by a battery of chemical analyses and found to be a relatively pure glucan. The CAG was weakly immunogenic in rabbits when administered in Freund's complete adjuvant. In monkeys (M irus) immunized via the parotid duct with an aqueous solution of CAG, a definite but weak serum IgG, IgM, IgA, and salivary IgA antibody response was observed. Absorption experiments showed that the CAG induced antibodies that cross reacted with Sephadex G-25 and others that reacted with unique determinants on CAG. Retention of native antigenic determinants through the purification procedures was verified by the observations that antiserums to CAG reacted with whole cells of S mutans and by the fact that antiserums to S mutans cells reacted with CAG.

[Genetic control of the synthesis of Newcastle shigella type-specific VI antigen]

The authors studied the localization of a determinant of the VI type antigen, Sh. newcastle being used in the capacity of donors and E. coli K12 as a recipient. The determinant of the VI type-specific antigen was apparently controlled by the chromosomal gene localized in the region of the histidine operon (on the left from it; 45% of linkage with the his marker).

Membrane-associated nucleotide sugar reactions: influence of mutations affecting lipopolysaccharide on the first enzyme of O-antigen synthesis

Both the synthesis of lipopolysaccharide O-antigen and the synthesis of peptidoglycan in Salmonella typhimurium proceed via membrane-bound glycosylated lipid intermediates. The first enzyme of each pathway transfers a sugar phosphate from a nucleotide sugar to the glycosyl carrier lipid (P-GCL). Each enzyme catalyzes an exchange reaction between the reaction product urine monophosphate, and the nucleotide sugar substrate. Several strains of S. typhimurium defective in lipopolysaccharide synthesis accumulate glycosylated lipid intermediates under appropriate conditions. In addition, strains lysogenic for phage P22 synthesize a glucose derivative of the carrier lipid. These strains were used to demonstrate the P/GCL requirement of the exchange reaction catalyzed by galactose-diphosphoglycosyl carrier lipid (GCL-PP-Gal) synthetase, the first enzyme of O-antigen synthesis. Enzyme activity is greatly reduced when glycosylated P-GCL accumulates on the cytoplasmic membrane. The exchange reaction catalyzed by the first enzyme of peptidoglycan synthesis is unaffected by the accumulation of O-antigen fragments on the carrier lipid and may interact with a different pool of P-GCL within the membrane. GCL-PP-Gal synthetase activity cannot be detected in the membranes of two rfa mutants that synthesize incomplete lipopolysaccharide core. Either the synthesis of GCL-PP-Gal synthetase or the stable integration of the enzyme into the membrane structure may be disrupted in the rfa mutants. Peptidoglycan synthesis is unaffected by the mutations affecting the core glycosyltransferases.

Translation of avian myeloblastosis virus RNA in a cell-free lysate of Escherichia coli

In a cell-free extract of E. coli, RNA from avian myeloblastosis virus directs the synthesis of a protein that is antigenically identical with the group-specific antigen 4, and other proteins, three of which correspond in molecular weight to group-specific antigens 1-3.

Mechanism of polymerization of the Salmonella O-antigen: utilization of lipid-linked intermediates

Cell envelope fractions from Salmonella can utilize exogenous lipid-linked intermediates for the synthesis of polymeric O-antigen. We describe a method for preparing aqueous suspensions of lipid intermediates and show that freezing and thawing of cell envelope-lipid intermediate mixtures is required for efficient synthesis. The lipid intermediates move freely in the hydrophobic environment of the membrane.