RESUMO
During sporulation Bacillus subtilis Mfd couples transcription to nucleotide excision repair (NER) to eliminate DNA distorting lesions. Here, we report a significant decline in sporulation following Mfd disruption, which was manifested in the absence of external DNA-damage suggesting that spontaneous lesions activate the function of Mfd for an efficient sporogenesis. Accordingly, a dramatic decline in sporulation efficiency took place in a B. subtilis strain lacking Mfd and the repair/prevention guanine oxidized (GO) system (hereafter, the ∆GO system), composed by YtkD, MutM and MutY. Furthermore, the simultaneous absence of Mfd and the GO system, (i) sensitized sporulating cells to H2O2, and (ii) elicited spontaneous and oxygen radical-induced rifampin-resistance (Rifr) mutagenesis. Epifluorescence (EF), confocal and transmission electron (TEM) microscopy analyses, showed a decreased ability of ∆GO ∆mfd strain to sporulate and to develop the typical morphologies of sporulating cells. Remarkably, disruption of sda, sirA and disA partially, restored the sporulation efficiency of the strain deficient for Mfd and the ∆GO system; complete restoration occurred in the RecA- background. Overall, our results unveil a novel Mfd mechanism of transcription-coupled-repair (TCR) elicited by 8-OxoG which converges in the activation of a RecA-dependent checkpoint event that control the onset of sporulation in B. subtilis.
Assuntos
Bacillus subtilis/genética , Bacillus subtilis/metabolismo , Reparo do DNA , Guanina/análogos & derivados , Recombinases Rec A/metabolismo , Transcrição Gênica , Bacillus subtilis/ultraestrutura , Dano ao DNA , Regulação Bacteriana da Expressão Gênica , Guanina/metabolismo , Mutação , Espécies Reativas de Oxigênio , Esporos BacterianosRESUMO
Neutral Electrolyzed Water (NEW) was tested in vitro and on artificially contaminated eggs against Salmonella enterica subsp. enterica or Escherichia coli. The antibacterial effect was measured 30â¯s after treatment. NEW microbicide activity results were compared against 2% citric acid and 0.9% saline solutions. NEW caused an in vitro decrease in Salmonella titers by Ë5.56 Log10 CFU mL-1 and in artificially contaminated eggs by Ë1.45 Log10 CFU/egg. When it was tested against E. coli, it decreased in vitro bacterial titers by Ë3.28 Log10 CFU mL-1 and on artificially contaminated eggs by Ë6.39 Log10 CFU/egg. The 2% citric acid solution caused an in vitro decrease of 0.4 Log10 CFU mL-1 of Salmonella and E. coli and on eggs artificially contaminated with E. coli or Salmonella there was a decrease of 0.06 and 0.62 Log10 CFU/egg respectively. We evaluated egg cuticle integrity by scanning electron microscopy after treatments with evaluated solutions; the 2% citric acid solution caused damage to the cuticle and exposed eggshell pores and no interaction of NEW or NaCl with the cuticle was observed. NEW treatment showed a fast-bactericidal effect in vitro and table eggs.
Assuntos
Antibacterianos/farmacologia , Casca de Ovo/microbiologia , Escherichia coli/efeitos dos fármacos , Salmonella enterica/efeitos dos fármacos , Água/farmacologia , Animais , Antibacterianos/química , Contagem de Colônia Microbiana , Casca de Ovo/efeitos dos fármacos , Ovos/microbiologia , Eletrólise , Escherichia coli/crescimento & desenvolvimento , Microbiologia de Alimentos , Concentração de Íons de Hidrogênio , Salmonella enterica/crescimento & desenvolvimento , Água/químicaRESUMO
Light and electron microscopy have been used to study cell structure for many years, but atomic force microscopy is a more recent technique used to analyze cells, mainly due to the absence of techniques to prepare the samples. Isolated molecules or organelles, whole cells, and to a lesser extent in situ cell structure have been observed by different atomic force microscopy imaging modes. Here, we review efforts intended to analyze in situ the cell structures using approaches involving imaging of the surface of semithin sections of samples embedded in resin and sections prepared with an ultramicrotome. The results of such studies are discussed in relation to their implications to analyze the fine structure of organelles at the nanoscale in situ at enhanced resolution compared to light microscopy.
Assuntos
Linfócitos/citologia , Linfócitos/ultraestrutura , Microscopia de Força Atômica , Organelas/ultraestrutura , Animais , Resinas Epóxi/química , Humanos , Linfócitos/química , Organelas/químicaRESUMO
Two untapered, heterocytous species were observed and collected from the intertidal and supratidal zones of the Mexican coastline of the Pacific Ocean near Oaxaca and from the Gulf of Mexico. These populations were highly similar in morphology to the freshwater taxon Petalonema incrustans in the Scytonemataceae. However, 16S rRNA sequence data and phylogenetic analysis indicated that they were sister taxa to the epiphyllic, Brazilian species Phyllonema aveceniicola in the Rivulariaceae, described from culture material. While genetic identity between the two new species was high, they differed significantly in morphology, 16S rRNA gene sequence identity, and sequence and structure of the 16S-23S ITS region. Their morphology differed markedly from the generitype of the previously monotypic Phyllonema, which has tapered, heteropolar, single-false branched trichomes with very thin or absent sheath. The two new species, Phyllonema ansata and Phyllonema tangolundensis, described from both culture and environmental material, have untapered, isopolar, geminately false branched trichomes with thick, lamellated sheaths, differences so significant that the species would not be placed in Phyllonema without molecular corroboration. The morphological differences are so significant that a formal emendation of the genus is required. These taxa provide a challenge to algal taxonomy because the morphological differences are such that one would logically conclude that they represent different genera, but the phylogenetic evidence for including them all in the same genus is conclusive. This conclusion is counter to the current trend in algal taxonomy in which taxa with minor morphological differences have been repeatedly placed in separate genera based primarily upon DNA sequence evidence.