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A study of the production of poly(γ-glutamic acid) (PGGA) by Bacillus licheniformis NCIMB 11709 grown on medium E in shake flasks at 30°C is reported. The enantiomeric composition of PGGA was found to be highly sensitive to the concentration of Mn++, especially when the ion is present in small amounts (⩽ 20 μM). Polymers with D-unit contents ranging from 10 to 90 % and Mw between 0.4 and 2.0 million g mol−1 were obtained for [Mn++] ranging from 0 to 1230 μM. Ultrasonic degradation was proven to be an effective method to reduce both the molecular weight and the polydispersity of naturally produced PGGA without disturbing the chemical constitution of the polymer. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 110–115, 1999.

The complement resistance of Aeromonas salmonicida strains grown under conditions promoting capsule formation was investigated using well characterized strains and their isogenic mutants. Complement resistance was previously studied using the same strains growing under noncapsulating conditions. The serum resistant strains were found to activate complement, but rapidly degrade C3b preventing productive formation of the lytic complex C5b-9. Isogenic lipopolysaccharide rough mutants grown under non-capsulating conditions were serum sensitive, binding a large amount of C3b and leading to productive formation of C5b-9. When grown under conditions promoting capsule formation, these mutants were partially resistant to complement because less C3b is bound to them and also partially degraded, with a concomitant reduction in lytic C5b-9.

Mesophilic Aeromonas hydrophila from serotypes O:11 and O:34 grown in a glucose-rich medium produce a capsule that can be seen under light and electron microscopy. The purified capsular polysaccharide has a composition qualitatively similar for strains O:11 and O:34, but quantitatively different. The capsular polysaccharides were immunogenic in rabbits, and did not cross-react with specific antibodies against either purified lipopolysaccharide from strains O:34 or O:11 or against the S-layer characteristic of strains from serotype O:11.

Extracellular polysaccharide (EPS) and capsular polysaccharide (CPS) production by Aeromonas salmonicida A450 and the influence of the capsule on cell surface properties were studied. A. salmonicida did not produce CPS or EPS when glucose, phosphate, magnesium chloride, or trace mineral components were absent from the medium. The addition of yeast extract improved capsule production. Neither EPS nor CPS formation depended on the C/N ratio, although it appeared to be influenced by the level of carbon and nitrogen in the culture. Both EPS and CPS production started at the end of the logarithmic growth phase. The amounts of EPS and CPS produced were not influenced by temperature changes between 15 and 20 degrees C and was maximal from pH 7 to 7.5. Cell surface properties were strongly influenced by capsule production; high CPS production was associated with enhanced cell hydrophilicity and autoagglutination. The effect of CPS on cell surface properties was independent of the presence of the surface protein array (A-layer).

Pseudomonas sp. EPS-5028 was examined for the ability to accumulate uranium from solutions. The uptake of uranium by this microorganism is very rapid and is affected by pH but not by temperature, metabolic inhibitors, culture time and the presence of various cations and anions. The amount of uranium absorbed by the cells increased as the uranium concentration of the solution increased up to 55 mg uranium/g cell dry weight. Electron microscopy indicated that uranium accumulated intracellularly as needle-like fibrils. Uranium could be removed chemically from the cells, which could then be reused as a biosorbent.

The influence of the capsule of Pasteurella piscicida on the cell surface properties of this microorganism as well as on the virulence and the capacity of the strains to grow in fish sera was examined. Although all the P. piscicida strains synthetized an additional exostructure in glucose-enriched-medium, only virulent strains constitutively synthetized capsule. The cell surface of all the P. piscicida isolates showed a low hydrophobic nature. No strains pelleted in broth culture (SP-) and all of them were stable after boiling (PAB). All isolates attached to the fish cell line CHSE-214 with values of adherence ranging from 2 to 5% of the initial bacterial inoculum. The presence of induced capsular material caused changes in some cell surface characteristics such as hydrophobicity and stability after boiling. A decrease in the adherence capacity of all the P. piscicida strains was also observed. However, the capsule increased the degree of virulence for fish of the nonpathogenic strains (LD50 was reduced in about 4 log) and conferred to all the isolates resistance to serum killing. Therefore, these results indicate that the presence of capsule can play an important role in the pathogenesis of P. piscicida.

The ability of several Aeromonas salmonicida strains grown under different conditions (capsulated and non-capsulated) to adhere to and invade two fish cell lines was compared. The level of adherence was slightly higher when the strains were grown under conditions promoting capsule formation than when the same strains were grown under conditions which did not promote capsule formation. However, the most significant difference among the wild-type strains grown under conditions promoting capsule formation was the ability to invade fish cell lines, which was significantly higher than when the same strains were grown under conditions which did not promote capsule formation. From these results we conclude that the capsular polysaccharide, in these strains, is an important factor for intracellular invasion.

Pasteurella piscicida grown in a glucose-rich medium produces a capsule that can be see under light and electron microscopy. The capsular polysaccharide was purified and characterized by chemical and HPLC analysis. The polymer has the composition glucose/mannose/N-acetylgalactosamine/galacturonic acid/acetic acid in the molar ratios of approximately 2.5:1.3:0.5:0.4:2.5. The polysaccharide was immunogenic in rabbits and did not cross-react with antibodies against the O-antigen lipopolysaccharide.

The influence of some ions in pre-growth culture medium on chromate reduction by resting cells of Agrobacterium radiobacter strain EPS-916 was investigated. The reduction was dependent on the Fe2+ content of the culture medium: the higher the iron content, the lower the reduction rate. The cells showed maximum chromate reduction when pre-grown in the presence of 0.243 μm Mg2+, 20 μm Ca2+ and 3.6 μm Mn2+. Chromate reduction was not affected by the addition of MgCl2, CdCl2, ZnCl2, MnCl2, Na2SO4 (1000 μm), and Na2MoO4 (100 μm) to the activity assays. However, activity was inhibited by the presence of Na2SO4 (10 mm), Na2MoO4 (200 μm) and ferric citrate.

E. coli CF3 isolated after the infection ofE. coli K12 C600 with the bacteriophage B278 produces quantities of extracellular exopoly-saccharide characterized by gas chromatography as composed of glucose, galactose and fucose in the molar ratio 1∶1∶1.2 and being partly acetylated. Solutions of the polysaccharide were pseudoplastic and its viscosity is constant at extreme pH (3.5–10) and compatible with temperature (90°C).

The effect of the inorganic phosphate concentration on the activity of the enzyme of alternate peripheral pathways of glucose catabolism was studied in Pseudomonas cepacia ATCC 17759. Growth with low glucose concentration (0.5% w/v) and 20 mM phosphate resulted in induced levels of the phosphorylative pathway enzymes when compared with the levels of these same enzymes in high glucose concentration (2% w/v). However, an expansion of the oxidative pathway was detected during growth with 0.5% (w/v) of glucose and high phosphate concentration (160 mM). Moreover, under high phosphate (160 mM) and high glucose (2% w/v) growth conditions, glucokinase activity was increased preferentially relative to levels of direct oxidative pathway enzymes.

The influence of 457 bacteria isolated from soil on spore germination by Aspergillus flavus was studied by light and scanning microscopy. Bacteria were found to be in physical association with the fungus. The bacteria were tested for antagonism against 11 fungal phytopathogens. A number of the bacterial antagonists displayed a wide spectrum in their activity against the fungi.

SUMMARY: Strain EPS-5028 is a free-living bacterium which contains R-bodies. By its morphology, biochemical characteristics and G + C content, strain EPS-5028 differs from the other known free-living R-body-containing bacteria, Pseudomonas avenae and Pseudomonas taeniospiralis. Phage and particles resembling phage heads were observed in cells induced with UV irradiation.

1. 71 strains of Pseudomonas aeruginosa were isolated from soils and tested for resistance to antibiotics and heavy metals. 2. 6% were resistant both to 12/14 drugs and 9/12 heavy metals tested.

Contamination of food and non-sterile medicaments was investigated in seven hospitals. Strains of Gram-negative bacilli isolated were identified and tested for resistance to chemotherapeutic agents and metallic salts. Four per cent of 530 samples of medicaments were contaminated with Pseudomonas aeruginosa and 6 per cent with other Gram-negative bacilli. Eighty-two per cent of 38 food samples were contaminated with Ps. aeruginosa and 63 per cent with other Gram-negative bacilli. Gram-negative bacilli showed a high degree of resistance to antibiotics and inorganic salts. Pyocine, serotyping, biotyping, antibiograms and metal resistograms suggested endemicity of Ps. aeruginosa and other Gram-negative bacilli in the hospitals.