In the aquatic environment, the physiological state of Vibrio cholerae can be affected by various environmental conditions (e.g., sunlight, pH, temperature, competition with other bacteria for nutrients, etc.). The effect of these factors on the toxigenicity of V. cholerae was investigated. Toxin production by 5 toxigenic strains of V. cholerae incubated in laboratory microcosms containing Rhizoclonium fontanum was tested at different time intervals. The microcosms were exposed to sunlight, and the V. cholerae were in competition for nutrients with the resident bacterial flora of R. fontanum. The increase or decrease in toxin production by V. cholerae recovered at different time intervals was measured by ELISA and compared with the parent strains. Results of the study demonstrated an increase in toxin production by V. cholerae O1 during survival with R. fontanum. It is concluded that various environmental conditions in the aquatic environment affect toxin production by V. cholerae.

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We determined the linkage of 16S, 23S, and 5S rRNA genes in several strains of Leptospira and Leptonema by DNA-DNA hybridization. Almost all the hybridizations in all leptospires used in these experiments gave two radioactive bands and the results strongly suggest that the number of the 16S and the 23S rRNA genes in those strains is two, respectively. In contrast with the larger rRNAs, the number of 5S rRNA gene was different. In the strains of leptospires, L. biflexa, which were non-parasitic, there are two genes for 5S rRNA, whereas only one gene for 5S rRNA is carried in L. interrogans, which were originally isolated as parasitic. Southern hybridization experiments suggest that those rRNA genes are interspersed on the leptospiral chromosome.

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The effect of norspermidine and its structurally related triamines on the cell-free polyphenylalanine synthesizing system from Vibrio parahaemolyticus was examined in connection with the requirement of the system for monovalent cation. In the absence of norspermidine, the maximal incorporation of [¹⁴C]phenylalanine into hot trichloroacetic acid insoluble material was observed under ionic conditions of 12mM Mg²⁺ and 50mM NH₄⁺. K⁺ could partially substitute for NH₄⁺, but Na⁺ could not. The addition of norspermidine to the polyphenylalanine synthetic reaction mixture not only lowered the optimal Mg²⁺ concentration, but it also stimulated the polyphenylalanine synthesis up to 2-fold with no significant increase in misincorporation of [¹⁴C]leucine. Other triamines having one or two methylene chains more than norspermidine were also effective in eliciting these effects. Furthermore, Na⁺ could not support the polyphenylalanine synthesis even in the presence of norspermidine and, on the contrary, inhibited the polyphenylalanine synthesis induced by NH₄⁺ regardless of whether norspermidine was present or not. These findings are discussed in comparison with the properties of other bacterial cell-free systems.

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Exposure of sensitive cells of Staphylococcus aureus to concentrations of gentamicin higher than the minimal inhibitory concentration, results in the recovery of low level resistant strains with a greatly altered phenotype (variants). Because the phenotypic alteration in these strains is so great the expected diagnostic characterization of these variants as S. aureus is obscured. Starting with a genetically-marked parent strain, a comprehensive cytological, physiological, morphological, genetic and biochemical analysis of the variants isolated from it was carried out. The genetic lineage of the variants to the parent was also established by DNA/DNA hybridization. Variants result from mutations in the hemin biosynthesis locus, the effect of which is to disrupt the synthesis of components of the electron transport system, lipid synthesis and selected nucleotide synthesis. Thus the strains are defective in aerobic and anaerobic respiration, (res^-), in active transport of aminoglycosides (which confers low level resistance), export of characteristic exo-enzymes, and in cell wall composition and structure.

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Various types of fimbriae on pathogenic Escherichia coli strains have been classified by their antigenicities and recognition specificities for receptors. However, the antigenicity of fimbrial proteins does not always correlate with the fimbrial recognition specificity. In this communication, the exact carbohydrate structures recognized by the fimbriae of two human uropathogenic E. coli strains, KS71 (O4) and IH11024 (O6), that have P-fimbrial antigen, were examined. Strain KS71 showed mannose-resistant (MR) hemagglutination (HA) of human blood group OP₁ phenotype erythrocytes, and its HA was inhibited by blood group P^k antigen, Gal(α, 1-4)Gal(β, 1-4)Glc-ceramide and P antigen, GalNAc(β, 1-3)Gal(α, 1-4)Gal(β, 1-4)Glc-ceramide but not by Forssman antigen, GalNAc(α, 1-3)GalNAc(β, 1-3)Gal(α, 1-4)Gal(β, 1-4)Glc-ceramide, as previously described in many papers. The cells also showed MR HA of sheep erythrocytes, which was potently inhibited by Forssman, and weakly by P und P^k antigens. These phenomena could not be explained by the above P adhesin specificity. This adhesin was called Forssman-like adhesin. Strain IH11024 also caused MR HA of sheep erythrocytes but not of human erythrocytes. The HA was inhibited specifically by Forssman but neither by P^k nor P antigen. This adhesin was completely different from P adhesin and Forssman-like adhesin in recognition of the carbohydrate epitope. This adhesin, until now called a pseudotype of P fimbriae, was renamed Forssman adhesin.

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Oral inoculation of human rotavirus MO strain (serotype 3) into 5-day-old BALB/c mice cause gastroenteritis characterized by diarrhea. Clinical symptoms, histopathological changes in the small intestine, and the detection of rotavirus antigen in enterocytes were all characteristic of rotavirus-induced gastroenteritis. Using this small animal model, passive protection of suckling mice against human rotavirus infection was achieved with the use of immunoglobulin (IgY) from the yolks of eggs of rotavirus-immunized hens. When IgY against a rotavirus strain homotypic to the challenge virus (MO strain) was administered in the mice, complete protection against rotavirus infection was achieved. On the other hand, with oral administration of IgY against a heterotypic strain (serotype 1, Wa strain), a lower protective effect was nevertheless obtained. The four different strains of human rotavirus (Wa, KUN, MO, and ST3) were inactivated in vitro by treatment with PSK, a protein-bound polysaccharide preparation, in a dose-dependent manner. Oral administration of 2.5mg of PSK caused a therapeutic effect on experimentally MO-infected suckling mice. The antiviral effect of PSK was indicated by the reduction of the duration of diarrhea.

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The incidence of Listeria monocytogenes contamination in raw milk from farm bulk tanks and silage was investigated monthly at 20 dairy farms in Aomori prefecture, Japan, from January to July in 1989. Listeria sp. was isolated from one sample (5%) of raw milk collected in May, but L. monocytogenes was not isolated from raw milk. L. monocytogenes was isolated from two samples of silage (10%) collected in June. Silage, cow feces, sawdust bedding, dust and soil in these farms were tested for listerias, and we confirmed listerias contamination of the environment in the dairy farms.

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A rapid small-scale method of extraction of lipopolysaccharide (LPS) and capsular polysaccharides was developed for the purpose of identification of chemotypes of LPS and serotypes of capsular antigens. Cell surface polysaccharides were prepared within less than 2hr from 1.5ml of broth or suspension of colonies cultured overnight. The preparations were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for LPS, and by double diffusion gel precipitation (Ouchterlony) test and blotting to nitrocellulose membrane for capsular polysaccharide. The analyses with the preparations obtained by the method could provide adequate results capable of identifying chemotypes of LPS and serotypes of capsular antigens.

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