Michele Bertoni Mann

Genetic variability of Bipolaris sorokiniana isolates using URP-PCR

Spot blotch disease, caused by Bipolaris sorokiniana, is one of the major diseases of wheat and is responsible for large losses of wheat crops worldwide. We used polymerase chain reaction (PCR) with universal rice primers (URP) for molecular characterization of 60 monosporic B. sorokiniana isolates from Brazil and other countries, and evaluated the diversity of the samples. PCR amplification generated 232 different DNA fragments ranging in size from 100 to 2018 bp. The primers URP-4R, URP-2R, and URP-1F generated greater numbers of amplified fragments (36, 30, and 25, respectively) from the single-spore isolates, and some diversity was observed among the isolates generated using these primers. The primers URP-2F, URP-6R, URP-17R, URP-30F, and URP-38F produced a pattern of monomorphic fragments and 73% of the isolates showed an average of 44 different DNA-amplified fragments. Primer URP-2F generated a 578-bp fragment that was common to 83.7% of the isolates; primer URP-6R generated a 548-bp fragment and primer URP-38F generated a 650bp product that was common to 89.1% and 80% of the isolates, respectively. The URP-PCR primers provided important information about the genetic profiles of the monosporic cultures, which showed intraspecific variability among the monoconidial isolates and among the monosporic cultures that originated from the same polysporic strain. Our results indicate that URPs are sensitive and give reproducible results for assaying the genetic variability of B. sorokiniana.

Bioaccumulation and distribution of selenium in Enterococcus durans

Selenium is an essential nutrient for all living organisms. Under appropriate conditions lactic acid bacteria (LAB) are capable for accumulating large amounts of trace elements, such as selenium, and incorporating them into organic compounds. In this study, the capacity of selenium bioaccumulation by Enterococcus durans LAB18s was evaluated. The distribution of organic selenium in selenium-enriched E. durans LAB18s biomass was analyzed, and the highest percentage of organic selenium was found in the fraction of total protein, followed by the fractions of polysaccharides and nucleic acids. When the protein fraction was obtained by different extractions (water, NaCl, ethanol and NaOH) it was demonstrated that alkali-soluble protein showed the higher Selenium content. Analysis of protein fractions by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that selenium was present in the proteins ranging from 23 to 100kDa. The cells were analyzed by scanning electron microscopy (SEM); scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) and transmission electron microscopy (TEM). SEM, TEM and SEM/EDS showed the morphology, the selenium particles bioaccumulated into and on the cells and the amounts of selenium present into the cells, respectively. Thus, the isolate E. durans LAB18s can be a promising probiotic to be used as selenium-enriched biomass in feed trials.