<p>In order to find suitable bacteria as concrete healing agents, we examined a total of 50 bacterial isolates from an alkaline soil sample. These isolates were subsequently tested for sporulation rates, ability to induce calcium carbonate precipitation, tolerance to alkaline conditions, as well as their capacity to heal cracks in mortar samples. Of the 50, two bacterial isolates showed promising results across all these test categories. These isolates were identified as <i>Bacillus horneckiae</i> and <i>B. kochii</i>. Both were able to grow on LB agar at a pH of 10, within 5 days had sporulation rates over 90% on the AR2A agar plates, and precipitated calcium carbonate on B4 agar plates. </p> <p>Both <i>B. horneckiae </i>and<i> B. kochii</i> had preferences for high alkaline environments. The OD 540nm readings of these two bacteria in pH 9 and 10 LB broths were significantly higher than the readings of their counterparts in pH 8 LB broth after 48 h of incubation. The growth of <i>B. horneckiae </i>and<i> B. kochii</i> in different concentrations of YE broths were tested. These two bacteria both had worse growth in 0.5 and 1% YE broths than in 2% YE broth. The spores of <i>B. horneckiae </i>and<i> B. kochii</i> were also tested for germinations in the same test environments. Results showed that either high pH or low nutrient levels did not have many impacts on spore germinations of these two bacteria. </p> <p>Calcium carbonate precipitation from these two bacteria were quantified. <i>Bacillus horneckiae </i>and<i> B. kochii </i>reduced approximately 980 and 650 ppm of free<i> </i>Ca²⁺ ion respectively from a 1/10 LB broth containing 2500ppm of Ca²⁺ within 7 d and precipitated CaCO₃.</p> <p>The mean viable counts of <i>B. horneckiae </i>and<i> B. kochii</i> decreased 1.2 and 1.5 orders of magnitude respectively in the first 24 h, dropped additional 0.6 and 0.4 orders of magnitude between day 1 and 14, and then, remained constant between day 14 and 28 after being mixed in mortar samples. Healing abilities were tested by incorporating bacterial spores in mortar samples. Cracks up to 0.25 mm were healed in mortar samples containing <i>B. horneckiae </i>or <i>B. kochii </i>spores<i>.</i> All the results suggested that both the bacterial isolates, <i>B</i>.<i> horneckiae </i>and<i> B. kochii</i>, may be used as bacterial healing agents in self-healing concretes.</p>

Made available in DSpace on 2016-12-08T16:24:16Z (GMT). No. of bitstreams: 1 PGCA14MA129.pdf: 560924 bytes, checksum: 728efdf249e90f0bd6744c133006c9a1 (MD5) Previous issue date: 2014-02-26 / Streptococcus suis is a important pathogen associated to many production and economical losses in the swine industry, in addition to its zoonotic importance. The aims of this study was evaluate the occurrence of Streptococcus suis type 2 in tonsil samples of healthy pigs at slaughter, comparing the bacterial isolation with PCR assay and to determine the presence of the EF factor (extracellular protein factor). Tonsil samples from 302 slaughtered pigs were collected from three abattoir. Isolation of S. suis was made in Columbia Blood Agar Base, and then bacterial phenotypic characterization was made using biochemical assays. The typification genus and species of the isolates was performed with the PCR technique for confirmation, and the presence of the capsular gene (type 2). In the comparison between the techniques, PCR was made directly from the tonsil samples for the 16SrRNA gene (S. suis), capsular genes (type 2) and also the ef gene. The pathogen was detected in 100% of the samples with the PCR, whereas only 84.1% were positive on the isolation technique. Upon confirmation of the S. suis isolates, four of them were negative to the 16S rRNA gene. PCR demonstrated higher sensibility on detecting the type 2 S. Suis, having 89.7% of positive samples against 88% from the isolates. The ef gene was detected in 28.4% of the samples, three of them being detected as the ef variant. Significant difference was found between the PCR and bacterial isolation for S. suis, detection demons that the molecular assay has a higher detection capability than isolation / Streptococcus suis é um patógeno responsável por muitas perdas produtivas e econômicas à suinocultura, além da importância zoonótica. O objetivo deste trabalho foi avaliar a ocorrência de Streptococcus suis tipo 2 a partir de tonsilas de suínos sadios no abate, comparando a técnica de isolamento bacteriano com a PCR e determinar a presença do fator protéico extracelular (EF). Foram coletadas tonsilas de 302 suínos provenientes de três frigoríficos, o isolamento foi realizado em Agar Sangue Columbia, após foi realizada a caracterização fenotípica. Esses isolados foram tipificados através da PCR para confirmação do gênero e da espécie, além da presença do gene capsular (tipo 2). Na comparação das técnicas foi realizado PCR diretamente das tonsilas para o gene 16S rRNA (S. suis), capsular (tipo 2) e também foi realizada pesquisa do gene ef (EF). Utilizando PCR diretamente das tonsilas, S. suis foi detectado em 100% das amostras, diferindo do isolamento em que 84,1% das amostras foram positivas. Na confirmação dos isolados sugestivos de S. suis, quatro deles foram negativos na PCR para o gene 16S rRNA. Na comparação para o tipo 2 a PCR demonstrou maior sensibilidade, detectando em 89,7% das tonsilas superando o isolamento, que detectou em 88% dos isolados. O gene ef foi detectado em 28,4% das amostras, sendo que em três amostras foi detectado o ef variante. Houve diferença significativa entre a PCR e o isolamento bacteriano para S. suis, demonstrando que a técnica molecular tem uma maior capacidade de detecção do que o isolamento