Análise comparativa da expressão gênica nas cepas selvagem W303 e pkc1∆ de Saccharomyces cerevisiae durante o processo de desrepressão metabólica.

A levedura Saccharomyces cerevisiae possui uma via MAP quinase de transdução de sinais composta por Pkc1p, Bck1p, Mkk1p e Mkk2p, e Mpk1p. Já foi descrito que esta via está envolvida no controle da integridade da parede celular, na resposta ao estresse osmótico, no crescimento de pseudo-hifas e no controle do metabolismo de carbono. Neste trabalho investigamos a participação de Pkc1p no controle da expressão de genes envolvidos no metabolismo de carbono. Para isto, fizemos uma analise da expressão gênica global através de microarranjos de DNA comparando a resposta global sob condições de repressão e desrepressão metabólica no mutante a pkc1∆ e na cepa selvagem correspondente W303. Os resultados obtidos indicaram uma diferença significativa na expressão global dos genes nas duas cepas analisadas. Vinte e oito genes envolvidos no metabolismo de carbono foram selecionados para validação por RT-PCR e os resultados confirmaram que sete genes foram mais expressos na cepa W303 quando comparada com a cepa e quatro genes foram mais expressos na cepa pkc1 ∆ quando comparada com a cepa selvagem. Análises “In silico” apontaram três fatores de transcrição Sok2p, Crz1p and Gcr1p, que podem estar envolvidos no controle da expressão gênica por Pkc1p. Experimentos utilizando plasmídeos contendo o gene da β- galactosidase sob controle dos promotores dos genes CYC1, HXT1 e SUC2 mostraram que a expressão destes genes se apresentava diminuída na cepa pkc1∆ para o gene HXT1, aumentada para o gene CYC1 e igual para o gene SUC2 quando comparada com a cepa selvagem W303. A atividade de Invertase apresenta-se significativamente diminuída na cepa pkc1 ∆ quando comparada com a cepa selvagem W303. Nossos resultados confirmam a participação da proteína Pkc1p na regulação da expressão gênica durante o processo de desrepressão metabólica

Activity of extracts and terpenoids from <i>Tontelea micrantha</i> (Mart. ex Schult.) A.C.Sm. (Celastraceae) against pathogenic bacteria

The pharmacological properties of plant extracts and phytochemicals, such as flavonoids and terpenoids, remain of great interest. In this work, the effect of extracts, friedelan-3,21-dione, and 3β-O-D-glucosyl-sitosterol isolated from Tontelea micrantha roots was evaluated against Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae, Klebsiella oxytoca and Escherichia coli. The antibacterial activity was evaluated by the minimum inhibitory and bactericidal concentrations (MIC and MBC, respectively), and the synergistic effect was assessed by the Checkerboard assay. Furthermore, the cytotoxicity of the plant-derived compounds against Vero cells was measured by the 3-(4 5-dimethylthiazol-2-yl)-2 5-diphenyltetrazolium bromide (MTT) method. The biological effects of the isolated compounds were predicted using the PASS online software. The chloroform and hexane extracts of T. micrantha roots showed promising antibacterial effect, with MIC in the range of 4.8–78.0 µg/mL. Further analyses showed that these compounds do not affect the integrity of the membrane. The combination with streptomycin strongly reduced the MIC of this antibiotic and extracts. The extracts were highly toxic to Vero cells, and no cytotoxicity was detected for the two terpenoids isolated from them (i.e. friedelan-3,21-dione and 3β-O-D-glucosyl-sitosterol; CC50 > 1000 μg/mL). Therefore, extracts obtained from T. micrantha roots significantly inhibited bacterial growth and are considered promising agents against pathogenic bacteria. The cytotoxicity results were very relevant and can be tested in bioassays.</p

Protective effect of ions against cell death induced by acid stress in Saccharomyces.

Saccharomyces boulardii is a probiotic used to prevent or treat antibiotic-induced gastrointestinal disorders and acute enteritis. For probiotics to be effective they must first be able to survive the harsh gastrointestinal environment. In this work, we show that S. boulardii displayed the greatest tolerance to simulated gastric environments compared with several Saccharomyces cerevisiae strains tested. Under these conditions, a pH 2.0 was the main factor responsible for decreased cell viability. Importantly, the addition of low concentrations of sodium chloride (NaCl) protected cells in acidic conditions more effectively than other salts. In the absence of S. boulardii mutants, the protective effects of Na1 in yeast viability in acidic conditions was tested using S. cerevisiae Na1-ATPases (ena1-4), Na1/H1 antiporter (nha1D) and Na1/H1 antiporter prevacuolar (nhx1D) null mutants, respectively. Moreover, we provide evidence suggesting that this protection is determined by the plasma membrane potential, once altered by low pH and low NaCl concentrations. Additionally, the absence or low expression/activity of Ena proteins seems to be closely related to the basal membrane potential of the cells