Counts of Pseudomonas ueruginosa had a high positive correlation with counts of coliforms, fecal streptococci, presumptive pathogenic yeasts, and heterotrophic bacteria in surface waters of Rio de Janeiro. Pseudomonas aeruginosa counts were notably higher in fresh than in marine waters, and it was isolated from about 50% of marine and 100% of nonchlorinated freshwater samples that passed the fecal coliform based Brazilian bathing standards. The most probable number method for enumeration of P. aeruginosa contained this microbe in 90% of the positive tubes from freshwater samples, but it had reduced selectivity in marine waters with 37.5% false negative and 35% false positive results. Microbial indicators of fecal pollution were not effective for noting the presence of P. aeruginosa in freshwaters.

A genetically modified strain of Pseudomonas fluorescens and its parent showed grossly similar decline rates following introduction into subtropical clay and sandy soils. In unplanted clay soil at pH 6.9 and 25°C, population densities declined progressively from about 10 s to 103 colony forming units (cfu) g-l dry soil over 75 days, but in unplanted sandy soil the introduced populations could not be detected after 25 days. In clay soil at pH 8.7 or 4.7, or at environmental temperature, decay rates were enhanced as compared to those at pH 6.9 and 25°C. Counts of introduced strains in clay bulk soil and in the rhizosphere and rhizoplane of maize suggested that the introduced bacteria competed well with the native bacteria, and colonized the roots at about 10 6 CfU g-1 dry root at 25°C, over 20 days. However, rhizoplane colonization was lower at environmental temperature. The decay rate of both strains was slower in planted than in unplanted sandy soil. The population densities in the rhizosphere and rhizoplane in the sandy soil were significantly lower than those in the clay soil. Both introduced strains colonized the maize roots in both soils, using seeds coated with bacteria in 1% carboxymethyl cellulose. Introduced cells were localized at different sites along the roots of plants developing in clay soil, with higher densities in the original (near the seeds) and root hair zones as compared to the intermediate zones. No significant difference was observed between the extent of root colonization of the genetically modified strain and its parent.

Pseudomonas strains were isolated from the rhizosphere of maize grown in yellow-red latosol from Rio de Janeiro, Brazil, to serve as a delivery system for heterologous genes and for risk assessment studies in tropical soils. Selected strains were modified by insertion of the cryIVB gene from Bacillus thuringiensis and tested for pathogenicity gene expression against larvae of a susceptible model species, Anopheles aquasalis. Modified strains Br8 and Br12 showed similar survival performance to their parental strains, and presented a viable density of 10(7) c.f.u./g dry soil 30 days after release. A strain of P. fluorescens (Br12) that presented positive results for gene expression and the best survival performance, was selected for risk assessment studies in soil microcosms.