Sourdough bacterial dynamics revealed by metagenomic analysis in Brazil.

This study dealt with the influence of the temperature on the bacterial dynamics of two spontaneously fermented wheat sourdoughs, propagated at 21 ± 1 °C (SD1) and 30 ± 1 °C (SD2), during nine backslopping steps (BS1 to BS9). Proteobacteria was the only phylum found in flour. Escherichia hermannii was predominant, followed by Kosakonia cowanii, besides species belonging to the genera Pantoea and Pseudomonas. After one step of propagation, Clostridium and Bacillus cereus group became predominant. Lactobacillus curvatus was found at low relative abundance. For the second backslopping step, Clostridium was flanked by L. curvatus and Lactobacillus farciminis. From BS4 (6th day) onward, lactic acid bacteria (LAB) became predominant. L. farciminis overcame L. curvatus and remained dominant until the end of propagations for both sourdoughs. At 21 °C, Bacillus, Clostridium, Pseudomonas, and Enterobacteriaceae were gradually inhibited. At the end of propagation, SD1 harbored only LAB. Otherwise, the temperature of 30 °C favored the persistence of atypical bacteria in SD2, as Pseudomonas and Enterobacteriaceae. Therefore, the temperature of 21 °C was more suitable for sourdough propagation in Brazil. This study enhanced the knowledge of temperature's influence on microbial assembly and contributed to the elucidation of sourdough microbial communities in Brazil

AFLP protocol comparison for microbial diversity fingerprinting

Over the last decade, several methods based on genomic DNA have been developed for the identification and genotyping of prokaryotic and eukaryotic organisms. These genomic methods differ regarding taxonomic range, discriminatory power, reproducibility, and ease of interpretation and standardization. The amplified fragment length polymorphism (AFLP) technique is a very powerful DNA fingerprinting technique for DNA of any source or complexity, varying in both size and base composition. In addition, this method shows high discriminatory power and good reproducibility allowing it to be efficient in discriminating at both the species and strain levels. The development and application of AFLP have allowed significant progress in the study of biodiversity and taxonomy of microorganisms. In the last years, the Applied Biosystems AFLP Microbial Fingerprinting Kit, now out of production, was widely used in various studies to perform AFLP characterization of selected bacteria strains (described by Vos et al. (Nucleic Acids Res 23(21):4407-4414, 1995)). Its replacement gives the possibility for laboratories to continue the use of the previous AFLP data as a reference for bacteria genetic fingerprinting analysis in biodiversity studies. To overcome this issue a result comparison, by using an improved AFLP protocol and the AFLP commercial kit, was performed. In particular, previous results on different species (Listeria monocytogenes, Lactobacillus plantarum, and Streptococcus thermophilus) obtained with the commercial kit were compared with the improved AFLP procedure to validate the protocol. When compared with the AFLP Microbial Fingerprinting Kit, the improved protocol shows high reproducibility, resolution, and overall, is a faster method with lower costs

A genome-wide approach in Arabidopsis thaliana to assess the toxicity of cadmium sulphide quantum dots

Cadmium sulphide quantum dots (CdS QDs) are used in the manufacture of a number of electronics products. Their small size allows their ready entry into living cells, but as yet no attempt has been made to assess their toxicity. Our aim was to exploit two Ds transposition-induced mutant lines of Arabidopsis thaliana which tolerated exposure to CdS QDs to identify the genetic basis of their tolerance. Both a genome-wide top-down (from mutant to genes) and a bottom-up (from gene expression to phenotype) approach were applied. The differential responses of the mutants compared to the wild type showed that sensitivity to CdS QDs was unrelated to sensitivity to Cd2+ ions. A transcriptomic analysis identified a number of genes whose transcript abundance was correlated with the tolerance. The phenotype of one of the mutants was correlated with the over-expression of ELM2, an MYB containing gene visited by a Ds transposon. Segregation analysis showed that the genetic basis of CdS QDs tolerance in both mutants was monogenic. The phenotype of the other mutant could be explained by the mutation of HCF101, a gene involved in photosynthesis