Extracellular hydrolytic enzymes produced by yeasts from Antarctic lichens.

In the Antarctic environment, yeasts are versatile eukaryotes that have shown wide dispersion in different substrates, producing active enzymes in extreme conditions, but their relevance in biotechnological applications is largely unknown. The aim of this study was to evaluate the production of extracellular hydrolases by yeasts isolated from Antarctic lichens and molecularly identify these isolates. From a total of 144 isolates on the screening, 109 (76%) produced at least one of the hydrolases tested, with most activities for proteases 59 (41%), cellulases 58 (40%), esterases 57 (39%), lipases 29 (20%), amylases 23 (16%) and pectinases 20 (14%). Among these isolates, 76 were identified, most belonged to the phylum Basidiomycota (n=73) with the dominance of Vishniacozyma victoriae (n=27), Cystobasidium alpinum (n=3), Mrakia niccombsii (n=3), Cystobasidium laryngis (n=2), Bannozyma yamatoana (n=2), Holtermanniella nyarrowii (n=2), and Glaciozyma martinii (n=2). This study is the first one reporting extracellular enzyme production by yeasts isolated from thallus of the species of Antarctic lichens Lecania brialmontii, Polycauliona candelaria, Usnea capillacea, Cladonia metacorallifera, and Polycauliona regalis. With these data, it's possible to confirm lichens as a source of hydrolase-producing yeasts, reinforcing the potential of these microorganisms in bioprospecting studies of catalytic molecules from polar regions that may be useful in promising biotechnological applications.

A short peptide with selective anti-biofilm activity against Pseudomonas aeruginosa and Klebsiella pneumoniae carbapenemase-producing bacteria.

Biofilm-related infections represent an enormous clinical challenge nowadays. In this context, diverse studies are underway to develop effective antimicrobial agents targeting bacterial biofilms. Here, we describe the antibacterial and anti-biofilm activities of a short, cationic peptide named R5F5, obtained from sliding-window analysis based on a peptide (PcDBS1R5) derived from Plasmodium chabaudi. Ten fragments were generated (R5F1 to F10) and submitted to initial antibacterial assays against Pseudomonas aeruginosa. As a result, R5F5 showed the highest antimicrobial activity. We therefore carried out further antibacterial and anti-biofilm assays against P. aeruginosa and Klebsiella pneumoniae carbapenemase-producing bacterial strains. R5F5 revealed selective anti-biofilm activity, as the peptide inhibited >60% biofilm formation in all cases from 8 to 64 µg·mL-1. Moreover, R5F5 was not hemolytic against mice erythrocytes at 640 µg mL-1. Cytotoxic effects on human lung fibroblast cells were not detected at 160 µg·mL-1. Structural studies revealed that R5F5 presents random coil conformations in water and 50% 2,2,2-trifluoroethanol (TFE)/water (v/v), whereas amphipathic, extended conformations were observed in contact with sodium dodecyl sulfate (SDS) micelles. Thus, here we report a novel peptide with selective anti-biofilm activity against susceptible and resistant bacterial strains, with no toxicity toward mammalian cells and that adopts a stable structure in anionic environment.

Microbial diversity in degraded and non-degraded petroleum samples and comparison across oil reservoirs at local and global scales.

Microorganisms have shown their ability to colonize extreme environments including deep subsurface petroleum reservoirs. Physicochemical parameters may vary greatly among petroleum reservoirs worldwide and so do the microbial communities inhabiting these different environments. The present work aimed at the characterization of the microbiota in biodegraded and non-degraded petroleum samples from three Brazilian reservoirs and the comparison of microbial community diversity across oil reservoirs at local and global scales using 16S rRNA clone libraries. The analysis of 620 16S rRNA bacterial and archaeal sequences obtained from Brazilian oil samples revealed 42 bacterial OTUs and 21 archaeal OTUs. The bacterial community from the degraded oil was more diverse than the non-degraded samples. Non-degraded oil samples were overwhelmingly dominated by gammaproteobacterial sequences with a predominance of the genera Marinobacter and Marinobacterium. Comparisons of microbial diversity among oil reservoirs worldwide suggested an apparent correlation of prokaryotic communities with reservoir temperature and depth and no influence of geographic distance among reservoirs. The detailed analysis of the phylogenetic diversity across reservoirs allowed us to define a core microbiome encompassing three bacterial classes (Gammaproteobacteria, Clostridia, and Bacteroidia) and one archaeal class (Methanomicrobia) ubiquitous in petroleum reservoirs and presumably owning the abilities to sustain life in these environments.