Francisco Congregado

URANIUM ACCUMULATION BY PSEUDOMONAS SP. EPS-5028

SummaryPseudomonas 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.

Biosynthesis and ultrasonic degradation of bacterial poly(γ-glutamic acid)

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.

Removal of uranium by an exopolysaccharide from Pseudomonas sp.

SummaryAccumulation of uranium (U) is reported for isolated exopolysaccharide produced by Pseudomonas sp. EPS-5028. A maximum uptake of 96 μg U/mg polymer was observed. In contrast, the maximum accumulation of uranium by deacylated polysaccharide was 46 μg/mg. This metal-complexing capacity observed suggests that the anionic reactive sites on the structure could be responsible for this activity. Metal uptake was affected by pH and was not affected by temperature. Expolysaccharide from Pseudomonas sp. EPS-5028 obeyed the Freundlich isotherm indicating single layer adsorption.

Occurrence of a capsule in Aeromonas salmonicida

Aeromonas salmonicida grown in a medium with excess glucose as carbon source produces both capsular and exocellular polysaccharides. The capsular polysaccharide is composed of glucose, mannose, rhamnose, N-acetylmannosamine and mannuronic acid in the molar ratios of approximately 5:3:0.75:2:1. The extracellular polysaccharide is similarly constituted, but in the molar ratios of approximately 4.75:10.5:1.5:2:1. The capsular and exocellular polysaccharides did not cross-react with monoclonal antibodies against the A-layer or the O-antigen lipopolysaccharide.

Effect of culture medium ions on chromate reduction by resting cells of Agrobacterium radiobacter

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.

Preliminary studies on the production ani composition of the extracellular polysaccharide synthesized byPseudomonas sp. EPS-5028

SummaryExopolysaccharide production byPseudomonas sp. strain EPS-5028 increased under conditions of high C/N ratios at the pH range 6.7–8 and 25°C. The polymer was formed from a variety of carbon substrates and contains D-glucose, D-galactose and uronic acid in the approximate molar ratio of 3∶2∶5. The polysaccharide produced is of high viscosity (1,600 cP; 1% polymer in D. I. water).

Method to assess antagonism of soil microorganisms towards fungal spore germination.

Biological control of phytopathogenic fungi has been suggested as an alternative to chemical control (Cook, 1976: Deacon, 1976: Espuny Tomas ef cl/.. 1977). There are several methods to control fungal plant pathogens in the soil without resorting to treatments with fungicides (Baker and Cook, 1974; Merriman et ul., 1974). One method of achieving biological control is to add selected antagonists to the soil and to establish them in the rhizospheres of crop plants (Mehrotra and Caludius. 1972). Before selected bacteria are added to soil it is essential to know their antagonistic potential (Broadbent et al., 1971). Several methods have been used as presumptive tests to determine the antagonism of microorganism to certain pathogens (Carter and Lockwood, 1957; Broadbent et al.. 1971: Kollmorgen and Jones, 1975). Because to ensure success for biological control many experiments are essential, a quick and easy procedure to assess the antagonistic potential of microorganisms was sought and is reported here.

New polysaccharide produced byE. coli CF3

SummaryE. 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).

Drug resistance patterns of Gram-negative bacteria isolated from food and non-sterile medicines in hospital environments

Abstract 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.

Nature of antagonism of fungi by bacteria isolated from soils

Abstract 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.