ABSTRACT
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 percent of the calcium, this strain thus has good potential for use on building materials.
ABSTRACT
The interactions between the nitrogen-fixing microorganism "Beijerinckia derxii" with two non-diazotrophic bacteria, either "Escherichia coli" or a faculty sulphur-oxidizing chemolitroph, 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