The effect of dihydrostreptomycin on the growth and induction of the enzyme, penicillinase, in Bacillus cereus has been studied. Two B. cereus variants were used: a sensitive culture, the growth of which was arrested by approximately 0.3 units of dihydrostreptomycin per milliliter of medium; and a resistant type which would grow in the presence of 2,000 units per milliliter of dihydrostreptomycin. This resistant strain was developed from the parent sensitive organism by successive transferring and plating techniques. The enzyme, penicillinase, was induced with penicillin and assayed manometrically. In the antibiotic-sensitive B. cereus, it was found that the formation of penicillinase, and not penicillinase action, was inhibited by dihydrostreptomycin. Further, total inhibition of penicillinase induction occurred with a concentration of antibiotic that inhibited growth of the organism. This inhibition of penicillinase formation was found to fit the mass law equation, xy = C, where x is the dihydrostreptomycin concentration, y is the fractional enzyme synthesis, and C is a constant. In the antibiotic-resistant B. cereus, neither growth nor penicillinase formation was inhibited by much higher concentrations of dihydrostreptomycin. A slight "partial dependence" on the antibiotic was noted. When antibiotic-resistant cultures, which had been grown in the absence of dihydrostreptomycin, were induced with penicillin in the absence and in the presence of streptomycin, there was, in the absence of the antibiotic, a longer lag period for the formation of penicillinase. That is, the resistant organism showed a slight dependence on streptomycin in the early stages of growth and enzyme induction. It was found that short periods of sonic treatment of suspensions of B. cereus produced an increase in the rate of penicillinase induction. Longer periods of sonic treatment, however, decreased the rate of enzyme induction. The results of this study - that streptomycin inhibits the formation of penicillinase in sensitive B. cereus but does not inhibit the action of this enzyme -were speculatively correlated with the known synergism between streptomycin and penicillin. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

The purpose of this investigation is to determine if there was a metabolic relationship between the actinomycetes and the gram positive, spore-forming becilli in surface waters, and, if such a relationship was evident, to relate the association to the disappearances of typical actinomycete tastes and odors from waters.

Orientador: Telma Teixeira Franco / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-07-24T03:01:02Z (GMT). No. of bitstreams: 1 Piza_FranciscoAssisToledo_M.pdf: 2251619 bytes, checksum: 74daaae73ee6ad4791486a0d5bd12b5a (MD5) Previous issue date: 1998 / Resumo: Este trabalho investigou a produção, extração e purificação da enzlma quitosanase. Planejamento fatorial fracionado 25-1 foi utilizado para obtenção de maiores níveis de quitosanase, avaliando o efeito das seguintes variáveis: concentração de quitosana, concentração de sulfato de amônio, pH, aeração e tempo de fermentação. As variáveis significativas para a produção da enzima quitosanase foram a concentração de sulfato de amônio, aeração, pH e as interações entre concentração de sulfato de amônio e aeração. A atividade máxima (l,5U/mL) foi alcançada em meio contendo 2,0% de quito sana, 4,0% de sulfato de amônio, aeração 10 (relação entre o volume do Erlenmeyer e o volume de meio de cultura), pH 5,8, 30°C em 16 horas de fermentação. Purificação primária da enzima quitosanase foi desenvolvida por partição em Sistemas de Duas Fases Aquosas (SDFA). Cinco composições de SDFA foram investigadas, sendo o melhor sistema para separação constituído de 22% PEG 1500 e 10% fosfato. Neste SDFA a enzima quitosanase foi recuperada na fase inferior (91%), obtendo-se um fator de purificação de 5,2. Purificação secundária da enzima quitosanase foi desenvolvida por cromatografia preparativa de troca iônica (CTI) em resina S-Sepharose (catiônica). A extração e purificação nas duas etapas (SDFA e CTI) resultaram em fator de purificação de 20 vezes e 66% de recuperação de quitosanase. Este processo de purificação desenvolvido é potencialmente interessante para a ampliação de escala, alcançando elevada recuperação em apenas duas etapas. A massa molecular da enzima quitosanase purificada (47 kDa) foi determinada por eletroforese em gel de poliacrilamida (SDS) e o ponto isoelétrico (8,8) foi determinado por focalização isoelétrica. / Abstract: A culture media for a wild strain of Baci/lus cereus was studied with regard to chitosanase production by means of experimental fractional fatorial design 25-1. The factors which were investigated were the chitosan concentration, the pH, the ammonium sulfate concentration, the aeration and the fennentation time. The factors having the strongest influence on chitosanase production were the ammonium sulfate concentration, aeration, pH and the interaction of the first two parameters. Optimal conditions for chitosan production (1.5 U/rnL) were in culture media containing 2.0% of chitosan, 4.0% of ammonium sulfate and with aeration 10 (Erlenmeyer flask volume and culture media volume ratio) at pH 5.8 at 30° for 16 hours. The enzyme was partially purified by partitioning in aqueous two-phase system (ATPS). Five different ATPS compositions were investigated for enzyme recovery and purity. The best system was made with 22% PEG 1,500, 10% phosphate, where the chitosanase was mainly collected in the botton phase (91% recovery and 5.2 fold the purification factor). A second-step purification was achieved by cation-exchange chromatography with S-Sepharose and salt gradient. The complete two-steps purification process developed achieved 66% chitosanase recovery and a 20 fold increase of the purification factor The apparent molecular weight of the chitosanase detennined by SDS-P AGE electrophoresis was 47 kDa and the observed isoelectric point was 8.8. / Mestrado / Mestre em Tecnologia de Alimentos

Bacillus cereus is a Gram-positive, spore-forming bacterium that is frequently identified as the causative agent of food-borne diseases and is also implicated in food spoilage of especially dairy products. The capacity of B. cereus to form biofilms on different substrata is of great concern in the food industry. Not only does biofilm formation cause economic loss by equipment failure, but contamination of food products via biofilm cells also raises safety concerns. Bacterial biofilms have been defined as structmed multicellular communities that form through a complex developmental process. In contrast to Gram-negative bacteria, biofilm formation by Gram-positive bacteria has only recently been examined. Relatively few genes have been identified that are required for these bacteria to form biofilms and little is known about how they coordinate biofilm formation. In order to contribute to the advancement of knowledge regarding the process of biofilm formation in Gram-positive bacteria, the aim of this investigation was essentially to identify and characterize genes involved in B. cereus biofilm formation. To investigate. B. cereus ATCC 14579 was subjected to transposon mutagenesis with the Tn917-LTVI transposon. Screening of a collection of3 500 insertional mutants for the ability to form biofilms at the solid-liquid-air interface of glass surfaces led to the identification of eight biofilm-impaired mutants. Each of the mutants contained a single transposon insertion, and no significant differences were observed in the planktonic growth rate between the B. cereus wild-type and biofilm-impaired mutant strains. The chromosomal transposon insertion in three of the mutants mapped to genes involved in purine biosynthesis (pur A, purC and purL), while the transposon insertion in two other mutants mapped to the ftsE gene and to the promoter region of the motA gene, respectively. In one of the mutants the transposon was located in the intergenic region between two divergently transcribed genes, which encodes a murein hydrolase exporter and nucleoside hydrolase, respectively. In the final two biofilmimpaired mutants the transposon was respectively mapped to genes encoding a putative membrane spanning protein and a putative protein of unknown function. Results obtained by quantitative real-time PCR assays indicated that expression of each of the identified B. cereus ATCC 14579 genes, with the exception of the motA gene, was up-regulated in the biofilm population. In the case of motA, expression of the gene was down-regulated 3.2-fold in the biofilm population and results obtained during the course of this investigation indicated that motility, rather than the presence of flagella, is required for B. cereus biofilm formation. Although this result is in agreement with that reported previously for B. subtilis, none of the other genes identified in this investigation have previously been implicated in biofilm formation by Gram-positive bacteria. / Dissertation (MSc)--University of Pretoria, 2010. / Microbiology and Plant Pathology / unrestricted

No description available.

No description available.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Dallas G. Hoover, Dept. of Animal & Food Sciences. Includes bibliographical references.

Orientador: Mirna Lucia Gigante / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-30T23:01:21Z (GMT). No. of bitstreams: 1 Ribeiro_MariaCeciliaEnes_D.pdf: 17038739 bytes, checksum: 54c8350faac4b14e773283e6e871aa78 (MD5) Previous issue date: 2015 / Resumo: O objetivo geral deste trabalho foi avaliar o efeito de diferentes matrizes na adesão e formação de biofilme em aço inoxidável por Bacillus cereus, bem como avaliar a eficiência dos procedimentos de higienização no controle de biofilmes de esporos desse micro-organismo. Nas duas primeiras etapas, avaliou-se a capacidade de adesão e formação de biofilme por B. cereus em aço inoxidável, com e sem prévio condicionamento da superfície, utilizando-se água, leite UHT desnatado e integral como matrizes e quatro diferentes tipos de inóculos, pool de células vegetativas de B. cereus isolados da indústria láctea, pool de esporos de B. cereus isolados da indústria láctea, células vegetativas da cepa de B. cereus ATCC 14579 e esporos da cepa de B. cereus ATCC 14579. Na terceira etapa do trabalho avaliou-se a influência da matriz condicionante (água e leite UHT integral), do meio de inoculação do pool de esporos de B. cereus (água e leite UHT integral) e do tempo de exposição (5 min (0,08h), 10, 24, 48 e 72 horas) sobre a adesão e formação de biofilme por B. cereus em aço inoxidável. Na quarta etapa, avaliou-se a eficiência de nove procedimentos de higienização na remoção dos biofilmes formados pelo pool de esporos de B. cereus em aço inoxidável. Todos os experimentos foram repetidos três vezes e os dados estatisticamente avaliados. A hidrofobicidade e o potencial zeta das superfícies dos esporos também foram avaliados. Os resultados das duas primeiras etapas indicaram que o pool de esporos de B. cereus isolados de indústria láctea apresentou a maior capacidade de adesão e formação de biofilme em aço inoxidável quando comparado aos outros tipos de inóculos, em todas as condições avaliadas. O maior grau de adesão de esporos de B. cereus (4,93 log UFC/cm2) foi observado ao se utilizar leite integral como matriz condicionante do aço inoxidável. Entretanto, comparando-se todas as matrizes, a menor adesão (3,01 log UFC/cm2) foi observada quando o pool de esporos de B cereus foi veiculado no leite integral sem prévio condicionamento da superfície. Na terceira etapa do trabalho observou-se que a adesão e formação de biofilme pelo pool de esporos de B. cereus foi maior quando inoculados em água, independente das matrizes de condicionamento. A adesão de B. cereus aumentou 1,02 e 0,3 log UFC/cm2 ao longo do tempo de exposição, quando o pool de esporos de B. cereus foi inoculado em água e leite integral, respectivamente. O biofilme de esporos veiculados na água apresentou maior resistência aos procedimentos de higienização. A sanitização com hipoclorito de sódio foi mais eficiente na remoção dos biofilmes quando comparada ao ácido peracético. O pool de esporos de B. cereus isolados da indústria láctea foi altamente hidrofóbico e apresentou carga negativa em uma ampla faixa de pH, com ponto isoelétrico de aproximadamente 3,0. Os esporos de B. cereus isolados da indústria láctea apresentaram maior capacidade de adesão ao aço inoxidável quando comparados aos outros inóculos avaliados, o que pode estar relacionado à alta hidrofobicidade e a baixa carga de superfície dos esporos / Abstract: The aim of this study was to evaluate the effect of different matrices on the adhesion and biofilm formation by Bacillus cereus on stainless steel, and to evaluate the effectiveness of sanitation procedures for controlling biofilm from spores of this microorganism. The first two parts were carried out in order to evaluate the adhesion and biofilm formation by B. cereus on stainless steel, with and without previous conditioning of the surface, using water, skim and whole UHT milk as matrices and four different types of inocula: a pool of B. cereus vegetative cells isolated from dairy industry, a pool of B. cereus spores isolated from dairy industry, vegetative cells of B. cereus ATCC 14579, and spores of B. cereus ATCC 14579. The third part of the study evaluated the effect of the conditioning matrix (water and whole UHT milk), the inoculation medium of pool of B. cereus spores (water and whole UHT milk) and exposure time (5 min (0.08h), 10, 24, 48 and 72 hours) on the adhesion and biofilm formation by B. cereus on stainless steel. In the fourth part, the effect of nine sanitation procedures on the removal of B. cereus spores biofilm was evaluated. All experiments were repeated three times and data were statistically evaluated. Hydrophobicity and zeta potential from spore¿s surface were also evaluated. Regarding the results to the first and second parts, the pool of B. cereus spores isolated from dairy industry had the highest ability of adhesion on stainless steel when compared to the other inocula, for all tested conditions. After stainless steel surface conditioning with whole milk, B. cereus spores showed the highest adhesion (4.93 log CFU/cm2). However, lower adhesion (3.01 log CFU/cm2) was observed when B. cereus spores were delivered in whole milk as compared to the other matrices, without previous conditioning of the surface. The results of the third part indicated that the adhesion and biofilm formation by the pool of B. cereus spores was higher when they were inoculated in water, regardless of the conditioning matrix. B. cereus spores adhesion increased by 1.02 and 0.3 log CFU/cm2 over exposure time, when the pool of B. cereus spores was inoculated into water and whole milk, respectively. Biofilm of B. cereus spores inoculated in water showed the highest resistance against all tested sanitation procedures. Sodium hypochlorite was the most effective sanitizer for removing all biofilms when compared to the peracetic acid. The pool of B. cereus spores isolated from dairy industry was highly hydrophobic and showed a negative charge at a wide pH range, with an isoelectric point of about 3.0. B. cereus spores isolated from dairy industry showed the highest ability to adhere on stainless steel when compared to the other inocula, which is possibly related to its higher hydrophobicity and lower spore surface charge / Doutorado / Tecnologia de Alimentos / Doutora em Tecnologia de Alimentos

Bacillus cereus is the most prevalent pathogenic Bacillus species found in foods, causing food spoilage and two types of toxin-mediated food poisoning known as the diarrhoeal and emetic syndromes. Other Bacillus species, particularly B. subtilis, B. licheniformis, B. brevis, B. pumilus and B. thuringensis, have also been recognised as food poisoning bacteria of increasing concern, with reports of outbreaks of diarrhoeal or emetic food poisoning. This study involved a systematic ecological investigation of Bacillus species isolated from rice products, commonly associated with Bacillus emetic food poisoning, using cultural and molecular methods. A centrifugation-plating method, more sensitive than the conventional spread plating method, was developed and used to determine the occurrence and biodiversity of Bacillus species in rice, a well known source of B. cereus. Eight different Bacillus species, B. cereus/B. thuringiensis, B. mycoides, B. subtilis/B. mojavensis, B. licheniformis, B. pumilus, B. sphaericus/B. fusiformis and B. megaterium, as well as Paenibacillus species, identified by partial rDNA sequencing, were isolated from raw (uncooked) and cooked rice products. The diversity of the isolates at the subspecies (strain) level was investigated using the RAPD-PCR typing technique, which proved to be useful for differentiating strains of bacilli, revealing broad diversity among the strains. Generally, different genotypes were found in raw and cooked rice, with some isolates of the same RAPD pattern found in both raw and cooked rice. The toxigenic potential of Bacillus isolates were also determined by molecular and immunological analysis as well as an MEKC method, developed in this study for quantitative analysis of the emetic toxin, cereulide. The results revealed that most isolates from the B. cereus group were potentially or actually toxigenic and some isolates were able to produce both diarrhoeal and emetic toxins. Other Bacillus species outside the B. cereus group were also shown to produce cereulide.

Thesis (M.S.)--University of Massachusetts Amherst, 2009. / Open access. Includes bibliographical references (p. 68-81).