Current status and emerging role of glutathione in food grade lactic acid bacteria.

Lactic acid bacteria (LAB) have taken centre stage in perspectives of modern fermented food industry and probiotic based therapeutics. These bacteria encounter various stress conditions during industrial processing or in the gastrointestinal environment. Such conditions are overcome by complex molecular assemblies capable of synthesizing and/or metabolizing molecules that play a specific role in stress adaptation. Thiols are important class of molecules which contribute towards stress management in cell. Glutathione, a low molecular weight thiol antioxidant distributed widely in eukaryotes and Gram negative organisms, is present sporadically in Gram positive bacteria. However, new insights on its occurrence and role in the latter group are coming to light. Some LAB and closely related Gram positive organisms are proposed to possess glutathione synthesis and/or utilization machinery. Also, supplementation of glutathione in food grade LAB is gaining attention for its role in stress protection and as a nutrient and sulfur source. Owing to the immense benefits of glutathione, its release by probiotic bacteria could also find important applications in health improvement. This review presents our current understanding about the status of glutathione and its role as an exogenously added molecule in food grade LAB and closely related organisms.

A New Reference Genome Shows the One-Speed Genome Structure of the Barley Pathogen Ramularia collo-cygni.

Ramularia leaf spot has recently emerged as a major threat to barley production world-wide, causing 25% yield loss in many barley growing regions. Here, we provide a new reference genome of the causal agent, the Dothideomycete Ramularia collo-cygni. The assembly of 32 Mb consists of 78 scaffolds. We used RNA-seq to identify 11,622 genes of which 1,303 and 282 are coding for predicted secreted proteins and putative effectors respectively.The pathogen separated from its nearest sequenced relative, Zymoseptoria tritici ∼27 Ma. We calculated the divergence of the two species on protein level and see remarkably high synonymous and nonsynonymous divergence. Unlike in many other plant pathogens, the comparisons of transposable elements and gene distributions, show a very homogeneous genome for R. collo-cygni. We see no evidence for higher selective pressure on putative effectors or other secreted proteins and repetitive sequences are spread evenly across the scaffolds. These findings could be associated to the predominantly endophytic life-style of the pathogen. We hypothesize that R. collo-cygni only recently became pathogenic and that therefore its genome does not yet show the typical pathogen characteristics. Because of its high scaffold length and improved CDS annotations, our new reference sequence provides a valuable resource for the community for future comparative genomics and population genetics studies.

Genomic and evolutionary insights into genes encoding proteins with single amino acid repeats.

Mutations causing expansion of amino acid repeats are responsible for 19 hereditary disorders. Repeats in several other proteins also show length variations. These observations prompted us to identify single amino acid repeat-containing proteins (SARPs) in humans and to understand their functional and evolutionary significance. We identified 8812 SARPs containing 17 146 repeat domains, each harboring 4 or more residues. In all, 5% of SARPs (471) showed repeat length variations, and nearly 84% of them (394) have repeats of 10 residues or less. We find that SARPs are involved in functions that require formation of multiprotein complexes. Nearly 78% (6859) of the SARPs did not find a paralogue in the human proteome, and such proteins are considered as orphan SARPs. Orphan SARPs show longer repeat stretches, longer peptide length, and lower expression levels as compared with SARPs belonging to protein family. Because the intensity of gene expression is known to relate inversely with the rate of protein sequence evolution, our results suggest that the orphan SARPs evolve faster than the familial forms and therefore are under a weaker selection pressure. We also find that while GC-rich codons are favored for coding the repeat tracts of SARPs, specific codons and not nucleotide motifs per se are selected, suggesting functional constraints placed on the usage of codons. One of the constraints could be the mRNA stability as clustering of rare codons is known to destabilize the transcripts and rare codons are not favored for coding repeat tracts. Genes encoding polymorphic SARPs show preferential localization toward the telomeric segments. Further, the sex-specific recombination rates of the chromosomal locus strongly correlate with the parental gender that influence the repeat instability in disorder caused by dynamic mutation. Therefore, instability associated with repeats might be driven by processes that are specific to sperm or oocyte development, and the recombination frequency might play a positive role in this process.