Influence of the carbon source on Gordonia alkanivorans strain 1B resistance to 2-hydroxybiphenyl toxicity

The viability of bacteria plays a critical role in the enhancement of fossil fuels biodesulfurization efficiency since cells are exposed to toxic compounds such as 2-hydroxybiphenyl (2-HBP), the end product of dibenzothiophene (DBT) biodesulfurization. The goal of this work was to study the influence of the carbon source on the resistance of Gordonia alkanivorans strain 1B to 2-HBP. The physiological response of this bacterium, pregrown in glucose or fructose, to 2-HBP was evaluated using two approaches: a growth inhibition toxicity test and flow cytometry. The results obtained from the growth inhibition bioassays showed that the carbon source has an influence on the sensitivity of strain 1B growing cells to 2-HBP. The highest IC50 value was obtained for the assay using fructose as carbon source in both inoculum growth and test medium (IC50-48 h=0.464 mM). Relatively to the evaluation of 2-HBP effect on the physiological state of resting cells by flow cytometry, the results showed that concentrations of 2-HBP >1 mM generated significant loss of cell viability. The higher the 2-HBP concentration, the higher the toxicity effect on cells and the faster the loss of cell viability. In overall, the flow cytometry results highlighted that strain 1B resting cells grown in glucose-SO4 or glucose-DBT are physiologically less resistant to 2-HBP than resting cells grown in fructose-SO4 or fructose-DBT, respectively

Nonextensive statistical mechanics applied to protein folding problem: kinetics aspects

A reduced (stereo-chemical) model is employed to study kinetic aspects of globular protein folding process, by Monte Carlo simulation. Nonextensive statistical approach is used: transition probability p i j between configurations i &#8594; j is given by p i j =[1 +(1 - q)&#916;Gi j/kB T ]1/(1-q), where q is the nonextensive (Tsallis) parameter. The system model consists of a chain of 27 beads immerse in its solvent; the beads represent the sequence of amino acids along the chain by means of a 10-letter stereo-chemical alphabet; a syntax (rule) to design the amino acid sequence for any given 3D structure is embedded in the model. The study focuses mainly kinetic aspects of the folding problem related with the protein folding time, represented in this work by the concept of first passage time (FPT). Many distinct proteins, whose native structures are represented here by compact self avoiding (CSA) configurations, were employed in our analysis, although our results are presented exclusively for one representative protein, for which a rich statistics was achieved. Our results reveal that there is a specific combinations of value for the nonextensive parameter q and temperature T, which gives the smallest estimated folding characteristic time (t). Additionally, for q = 1.1, (t) stays almost invariable in the range 0.9 < T < 1.3, slightly oscillating about its average value <img border=0 width=32 height=32 src="../../../../../../../img/revistas/bjp/v39n2a/a16txt01.gif" align=absmiddle > or = 27 ±&#963;, where &#963; = 2 is the standard deviation. This behavior is explained by comparing the distribution of the folding times for the Boltzmann statistics (q &#8594; 1), with respect to the nonextensive statistics for q = 1.1, which shows that the effect of the nonextensive parameter q is to cut off the larger folding times present in the original (q &#8594; 1) distribution. The distribution of natural logarithm of the folding times for Boltzmann statistics is a triple peaked Gaussian, while, for q = 1.1 (Tsallis), it is a double peaked Gaussian, suggesting that a log-normal process with two characteristic times replaced the original process with three characteristic times. Finally we comment on the physical meaning of the present results, as well its significance in the near future works

The importance of lizards and small mammals as reservoirs for Borrelia lusitaniae in Portugal

Borrelia lusitaniae is a pathogen frequent in the Mediterranean area. Apart from lizards, evidence for birds and small mammals as competent reservoirs for this genospecies has been occasional. We collected questing ticks, skin biopsies and Ixodes sp. ticks feeding on lizards, birds and small mammals in a B. burgdorferi s.l. enzootic area to assess their importance in the maintenance of B. lusitaniae. B. lusitaniae was the most prevalent genospecies in questing ticks and was commonly found in larvae feeding on Psammodromus algirus. One biopsy infected with B. lusitaniae was collected from the tail of one Podarcis hispanica, which suggests systemic infection. I. ricinus larvae feeding on Apodemus sylvaticus were infected with B. lusitaniae but with a lower prevalence. Our results reinforce the importance of lizards as reservoirs for B. lusitaniae, suggesting that P. algirus, in particular, acts as main reservoir for B. lusitaniae in Portugal

Relação entre mudanças no uso da terra e o relevo em uma área piloto da zona da mata sul de Pernambuco.

A identificação, a interpretação, a organização e a espacialização de características ambientais tais como: solos, relevo, clima, uso e ocupação, entre outras, numa escala adequada, são de fundamental importância quando se pretende elaborar uma estratégia de desenvolvimento rural em bases sustentáveis. A expansão da cultura da cana-de-açúcar na Zona da Mata Sul de Pernambuco, motivada pelo Proálcool, não atendeu a esses requisitos, principalmente, com relação ao relevo. Desta forma, o presente estudo tem como objetivos: 1) elaborar os mapas de relevo (altitude e declividade), cobertura ?recente? e cobertura ?pretérita?; 2) avaliar as mudanças na cobertura de mata Atlântica; 3) avaliar a adequação do uso da terra ao relevo de uma área piloto da Zona da Mata Sul de Pernambuco. A área selecionada (aproximadamente 75.000 ha) foi delimitada utilizando mapas planialtimétricos na escala 1:25.000. Esses mapas foram usados na obtenção do modelo digital de terreno (MDT) e extração das áreas com mata Atlântica no início da década de 1970. O mapa de uso e cobertura ?recente? foi obtido usando imagens do sensor Landsat 5 TM. Aproximadamente 50% da área apresenta relevo forte ondulado e montanhoso impróprias para o uso agropecuário. Apesar disso, a cana-de-açúcar ocupa 45% dessas áreas, cuja aptidão é para a preservação da fauna e da flora e recreação. Dos cerca de 24.000 ha de matas existentes na década de 70, 16.000 ha foram removidos. Dos atuais 11.907 ha de mata Atlântica, aproximadamente 4.052 ha são de novas formações

Mudanças no uso e na cobertura do solo em uma área piloto da mesorregião agreste de Pernambuco.

Visando a subsidiar estudos das alterações no balanço de emissões de gases de efeito estufa e balanço de carbono em ambientes terrestres para as diversas fisionomias vegetais, este trabalho teve como objetivo avaliar, com base em imagens de satélites da série Landsat, as mudanças ocorridas, entre 1987 e 2013, no uso e na ocupação do solo. A área piloto foi representada pela folha Venturosa (SC24-X-B-V), escala 1:100.000. Foram utilizadas imagens radiometricamente corrigidas dos sensores Landsat 5 TM de 1987 e Landsat 8 LDCM de 2013. Utilizou-se a classificação supervisionada pelo método da máxima verossimilhança considerando-se as seguintes classes de cobertura: agricultura, pastagem, caatinga densa, caatinga aberta, solo exposto e corpos de água. Nos dois anos considerados a cobertura foi mantida em cerca de 43% da área. A área de agricultura não foi alterada. A perda de vegetação nativa de melhor qualidade (caatinga densa) representou uma perda de lenha de aproximadamente 5.000.000 st. O aumento da área de pastagem em cerca de 10% foi atribuído ao aumento do rebanho bovino entre os anos de 1986 e 1996. O aumento nas áreas de caatinga aberta e de solo exposto pode indicar um aumento na degradação dos solos