Effect of culture medium on biocalcification by Pseudomonas Putida, Lysinibacillus Sphaericus and Bacillus Subtilis

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.

Recent advances in the study of biocorrosion - an overview

Biocorrosion processes at metal surface are associated with microorganisms, or the products of their metabolic activities including enzymes, exopolymers, organic and inorganic acids, as well as volatile compounds such as ammonia or hydrogen sulfide. These can affect catholic and/or anodic reactions, thus altering electrochemistry at the biofilm/metal interface. Various mechanisms of biocorrosion, reflecting the variety of physiological activities carried out by different types of microorganisms, are identified and recent insights into these mechanisms reviewed. Many investigations have centered on the microbially-influenced corrosion of ferrous and copper alloys and particular microorganisms of interest have been the sulfate-reducing bacteria and metal (especially manganese)-depositing bacteria. The importance of microbial consortia and the role of extracellular polymeric substances in biocorrosion are emphasized. The contribution to the study of biocorrosion of modern analytical techniques, such as atomic force microscopy, Auger electron, X-ray photoelectron and Mössbauer spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy and microsensors, is discussed

Algae and cyanobacteria on painted surfaces in southerns Brazil

Algae and cyanobacteria disfigure the external surfaces of buildings and may cause their physico-chemical deterioration. Even though the climate in Brazil is humid, there is no published literature on this problem. The objective of this work was to identify the major photographs present on Brazilian constructions in residential, urban and rural sites. The algal and cyanobacterial types present on discolored surfaces of painted buildings in nine different municipalities in Brazil, all lying between latitudes 19§ South and 30§South, were examined. A total of 816 different organisms was detected in 58 sites. Approximately 63 (per cent) were single-celled or colonial organisms. The cyanobacterial genus, Synechocystis, was the most biodiverse and frequently comprised the major biomass. It was present in 63,4 (per cent) of sites. Second and third most frequently detected were Oscillatoria and the algal genus, Chorella, respectively. The latter organism showed the most widespread occurrence (72.4 per cent). Cyanobacteria were the most important colonizers, especially at urbans sites, where over 62 (per cent) of the organisms detected belonged to this class. Filamentous photographs were found in smaller numbers than non-filamentous at all locations.

The importance of biofilms in microbial deterioration of constructional materials

Constructional materials, such as concrete, stone, wood, plastic, painted surfaces and metal, are colonized by bacteria, algae and fungi, which form biofilms on the surfaces acceleranting deteriotion of the structure. The mechanisms of such deterioration, the major microbial genera involved some and of factors which can affect the degree of colonization and attack are discussed. The major factor determining microbial growth on constructional materials is moisture and the importance of correct design of structures to avoid the ingress of water is pointed out.

A theoretical model describing the influence of diffusion on microbidal action in biofilms

Um dos métodos padröes para avaliar a atividade de um microbicida é a medida da taxa de morte de células sésseis ou em suspensäo (planctônicas). Sabe-se que, na maioria dos casos, células sésseis säo mais resistentes às substâncias inibidoras do que as células planctônicas. Este aumento de resistência pode ser devido à mudança na fisiologia das células ou à falta de penetraçäo do microbicida no biofilme. Um modelo que demonstra a influência da taxa de penetraçäo de microbicidas sobre a morte das células é apresentado. Os cálculos podem ser feitos por computador utilizando-se programas de planilhas eletrônicas. Os resultados mostram que o biofilme reduz a taxa de morte das células, quando a fisiologia microbiana näo é alterada. Pelo modelo, pode-se estimar a concentraçäo de microbicida necessária para matar tanto células sésseis quanto células em suspensäo, no mesmo estado fisiológico, num tempo

Microbial contamination of stored diesel oil in Brasil

As refinarias e sistemas de distribuiçäo tem enfrentado problemas com a contaminaçäo microbiana em óleo diesel armazenado. A atividade microbiana nesses sistemas leva à produçäo de uma biomassa na interface óleo/água, provocando problemas operacionais, como entupimento de filtros, tubulaçöes, alteraçäo na qualidade do combustível. O controle dessa contaminaçäo pode envolver o uso de agentes químicos, como os biocidas. O objetivo desse trabalho foi selecionar biocidas eficientes para o controle de fungos, bactérias aeróbicas e bactérias redutoras de sulfato (BSR), que foram isoladas de óleo diesel comum, urbano e naval, armazenados em tanques de refinaria no Rio Grande do Sul. Dois biocidas (um composto quaternário de amônio e uma mistura de isothiazolona) foram selecionados por apresentarem alta eficácia, em baixas concentraçöes para os principais contaminantes, como fungos do gênero Aspergillus e Hormoconis, BSR e bactérias aeróbias do gênero Pseudomonas e Bacillus

Cationic interactions in the lipoplysaccharide of Desulfovibrio vulgaris

Foram utilizadas as técnicas de cromatografia à liquido de alto desempenho (HPLC), análise por raio-X EDAX) e eletroforese em gel de poliacrilamida (SDS-PAGE) na investigaçäo das interaçöes entre vários cátions e lipopolissacarídeo (LPS) extraído da espécie bacteriana Desulfovibrio vulgaris. O LPS demonstrou afinidades variáveis para diferentes íons divalentes. Eletrodiálise removeu a maioria dos íons Fe (II) do LPS e resultou num aumento dos íons Ca. A HPLC e SDS-PAGE demonstraram diferenças na estrutura de LPs isolado de células ricas ou pobres em Fe(II), que indicaram que o Fe(II)