No abstract

This work reports the photophysical and biological evaluation of five cationic porphyrins as photosensitizers (PS) for the photodynamic inactivation (PDI) of Penicillium chrysogenum conidia. Two different cationic porphyrin groups were synthesized from 5,10,15,20-tetrakis(4-pyridyl)porphyrin and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin. The photostability and singlet oxygen generation studies showed that these molecules are photostable and efficient singlet oxygen generators. PDI experiments of P. chrysogenum conidia conducted with 50 μmol L(-1) of photosensitiser under white light at a fluence rate of 200 mW cm(-2) over 20 min showed that the most effective PS caused a 4.1 log reduction in the concentration of viable conidia. The present results show that porphyrins 1a and 1b are more efficient PSs than porphyrin 2a while porphyrins 1c and 2b show no inactivation of P. chrysogenum. It is also clear that the effectiveness of the molecule as PS for antifungal PDI is strongly related with the porphyrin substituent groups, and consequently their solubility in physiological media. The average amount of PS adsorbed per viable conidium was a determining factor in the photoinactivation efficiency and varied between the different studied PSs. Cationic PSs 1a and 1b might be promising anti-fungal PDI agents with potential applications in phytosanitation, biofilm control, bioremediation, and wastewater treatment.

As is the case for Saccharomyces boulardii, Saccharomyces cerevisiae W303 protects Fisher rats against cholera toxin (CT). The addition of glucose or dinitrophenol to cells of S. boulardii grown on a nonfermentable carbon source activated trehalase in a manner similar to that observed for S. cerevisiae. The addition of CT to the same cells also resulted in trehalase activation. Experiments performed separately on the A and B subunits of CT showed that both are necessary for activation. Similarly, the addition of CT but not of its separate subunits led to a cyclic AMP (cAMP) signal in both S. boulardii and S. cerevisiae. These data suggest that trehalase stimulation by CT probably occurred through the cAMP-mediated protein phosphorylation cascade. The requirement of CT subunit B for both the cAMP signal and trehalase activation indicates the presence of a specific receptor on the yeasts able to bind to the toxin, a situation similar to that observed for mammalian cells. This hypothesis was reinforced by experiments with 125I-labeled CT showing specific binding of the toxin to yeast cells. The adhesion of CT to a receptor on the yeast surface through the B subunit and internalization of the A subunit (necessary for the cAMP signal and trehalase activation) could be one more mechanism explaining protection against the toxin observed for rats treated with yeasts.

Membrane phospholipids of S. warneri are molecular targets of the photoinactivation process induced by Tri-Py(+) -Me-PF. The overall modification in the relative amount of phospholipids and the formation of lipid hydroxides and hydroperoxides indicate the lethal damage caused to photosensitized bacterial cells.

Sponge species have been deemed high microbial abundance (HMA) or low microbial abundance (LMA) based on the composition and abundance of their microbial symbionts. In the present study, we evaluated the richness and composition of bacterial communities associated with one HMA sponge (Xestospongia testudinaria; Demospongiae: Haplosclerida: Petrosiidae), one LMA sponge (Stylissa carteri; Demospongiae: Scopalinida -Scopalinidae), and one sponge with a hitherto unknown microbial community (Aaptos suberitoides; Demospongiae: Suberitida: Suberitidae) inhabiting the Misool coral reef system in the West Papua province of Indonesia. The bacterial communities of these sponge species were also compared with seawater and sediment bacterial communities from the same coastal coral reef habitat. Using a 16S rRNA gene barcoded pyrosequencing approach, we showed that the most abundant phylum overall was Proteobacteria. The biotope (sponge species, sediment or seawater) explained almost 84% of the variation in bacterial composition with highly significant differences in composition among biotopes and a clear separation between bacterial communities from seawater and S. carteri; X. testudinaria and A. suberitoides and sediment. The Chloroflexi classes SAR202 and Anaerolineae were most abundant in A. suberitoides and X. testudinaria and both of these species shared several OTUs that were largely absent in the remaining biotopes. This suggests that A. suberitoides is a HMA sponge. Although similar, the bacterial communities of S. carteri and seawater were compositionally distinct. These results confirm compositional differences between sponge and non-sponge biotopes and between HMA and LMA sponges.

In the present study, we used Illumina sequencing to explore the prokaryote communities of 17 demosponge species and how they compare with bacterial mat, sediment and seawater samples (all sampled from coral reef habitat in Taiwan and Thailand). The studied sponge species formed three clusters. OTU richness and evenness were by far highest in the sediment and bacterial mat biotopes. There were pronounced differences in OTU richness and evenness among clusters and also considerable variation among certain host species within clusters. Additionally, the relative abundance of some prokaryotic taxa also differed among clusters with Poribacteria, for example, being recorded in all sponge species, but with very low relative abundances in species of two of the three clusters. This sponge-associated phylum was, however, recorded at relatively high mean abundance in bacterial mat samples, which also housed relatively high abundances of actinobacterial and Chloroflexi members. Our results support the HMA status of the species Aaptos lobata, Hyrtios erectus, Pseudoceratina purpurea and Xestospongia testudinaria, which clustered together and LMA status of the species Acanthella cavernosa, Echinodictyum asperum, Jaspis splendens, Ptilocaulis spiculifer, Stylissa carteri and Suberites diversicolor, which also clustered together. Other species (Agelas cavernosa, Agelas nemoechinata, Acanthostylotella cornuta, Paratetilla sp., Hymeniacidon sp. and Haliclona cymaeformis) deviated somewhat from the typical HMA/LMA dichotomy and formed a strongly supported cluster.

In this work we report an optimized protocol for simultaneous extraction of DNA and RNA from soil matrices. Treatment of soil matrices with ethanol followed by bead-beating worked as a successful strategy to lyse the cells without considerable degradation of nucleic acids, resulting in DNA and RNA of good yield and integrity. The reverse transcribed RNA could be amplified with primers targeting a glutamine synthetase (glnA) gene fragment. From both DNA and cDNA, 16S rDNA fragments were amplified and analyzed by Denaturing Gradient Gel Electrophoresis (DGGE). The method was applied to soil and rhizosphere (strawberry and oilseed rape) samples. Two other protocols for the extraction of nucleic acids from soil were applied to the same set of samples in order to compare the methods in terms of efficiency and reproducibility. The DGGE profiles indicated no relevant differences between the patterns obtained. The method described here is suitable for rapid processing of many samples and therefore appropriate for ecological studies.

Five strains of Rhodotorula mucilaginosa were tested for the ability to accumulate free and complexed silver ions by metabolism-dependent and -independent processes. The ability to take up Ag + was observed in both live and dead biomass, whereas silver dicyanide [Ag (CN)2-] uptake was strictly glucose dependent. In contrast to Ag (CN)2-, glucose addition inhibited by 16 to 25% the Ag + uptake rate of living UFMG -Y02, Y27, and Y35 cells, while strains CBS 316 and UFMG-Y01 showed an improved uptake rate of about 115% and 13%, respectively. The Langmuir sorption model was used to evaluate the silver sorption capability of the R. mucilaginosa strains. The calculated qmax value suggested that R. mucilaginosa strains UFMG-Y27 had the highest loading capacity. The type strain CBS 316 had the lowest qmax but showed the highest affinity for silver ions. The results provided by the Fourier Transform Infra Red analysis (FTIR) suggest that C=O groups represent the main reactive site for silver uptake by the strain UFMG-Y27.