The objective of this study is to investigate the efficiency of calcium carbonate bioprecipitation by Lysinibacillus sphaericus, Bacillus subtilis and Pseudomonas putida, obtained from the Coleção de Culturas do Instituto Nacional de Controle de Qualidade em Saúde (INCQS), as a first step in determining their potential to protect building materials against water uptake. Two culture media were studied: modified B4 containing calcium acetate and 295 with calcium chloride. Calcium consumption in the two media after incubation with and without the bacterial inoculum was determined by atomic absorption analysis. Modified B4 gave the best results and in this medium Pseudomonas putida INQCS 113 produced the highest calcium carbonate precipitation, followed by Lysinibacillus sphaericus INQCS 414; the lowest precipitation was produced by Bacillus subtilis INQCS 328. In this culture medium XRD analysis showed that Pseudomonas putida and Bacillus subtilis precipitated calcite and vaterite polymorphs while Lysinibacillus sphaericus produced only vaterite. The shape and size of the crystals were affected by culture medium, bacterial strain and culture conditions, static or shaken. In conclusion, of the three strains Pseudomonas putida INQCS 113 in modified B4 medium gave the best results precipitating 96% of the calcium, this strain thus has good potential for use on building materials.

Co-culturas com a bactéria fixadora de nitrogênio Beijerinckia derxii e duas bactérias não diazotróficas (Escherichia coli e uma bactéria quimiolitotrófica facultativa oxidante de enxofre) foram empregadas para o estudo de interações bacterianas. B. derxii foi colocada em contato direto e indireto com E. coli. Um aumento no número de UFC e a manutenção da viabilidade das não diazotróficas foi promovido por B. derxii, porém seu crescimento e atividade da nitrogenase não foram afetadas por nenhuma das parceiras.

The interactions between the nitrogen-fixing microorganism Beijerinckia derxii with two non-diazotrophic bacteria, either Escherichia coli or a facultative sulphur-oxidizing chemolitotroph, were studied in mixed cultures. Direct and indirect contact between B. derxii and E. coli were tested. B. derxii increased CFU numbers and/or maintained the viability of the non-diazotrophic bacteria, but neither growth nor nitrogenase activity of the nitrogen-fixing bacterium were affected by either partner.