Phylogeny and structural modeling of the transcription factor CsqR (YihW) from Escherichia coli.

CsqR (YihW) is a local transcription factor that controls expression of yih genes involved in degradation of sulfoquinovose in Escherichia coli. We recently showed that expression of the respective gene cassette might be regulated by lactose. Here, we explore the phylogenetic and functional traits of CsqR. Phylogenetic analysis revealed that CsqR had a conserved Met25. Western blot demonstrated that CsqR was synthesized in the bacterial cell as two protein forms, 28.5 (CsqR-l) and 26 kDa (CsqR-s), the latter corresponding to start of translation at Met25. CsqR-s was dramatically activated during growth with sulfoquinovose as a sole carbon source, and displaced CsqR-l in the stationary phase during growth on rich medium. Molecular dynamic simulations revealed two possible states of the CsqR-s structure, with the interdomain linker being represented by either a disordered loop or an ɑ-helix. This helix allowed the hinge-like motion of the N-terminal domain resulting in a switch of CsqR-s between two conformational states, "open" and "compact". We then modeled the interaction of both CsqR forms with putative effectors sulfoquinovose, sulforhamnose, sulfoquinovosyl glycerol, and lactose, and revealed that they all preferred the same pocket in CsqR-l, while in CsqR-s there were two possible options dependent on the linker structure.

Sense and antisense RNA products of the uxuR gene can affect motility and chemotaxis acting independent of the UxuR protein.

Small non-coding and antisense RNAs are widespread in all kingdoms of life, however, the diversity of their functions in bacteria is largely unknown. Here, we study RNAs synthesised from divergent promoters located in the 3'-end of the uxuR gene, encoding transcription factor regulating hexuronate metabolism in Escherichia coli. These overlapping promoters were predicted in silico with rather high scores, effectively bound RNA polymerase in vitro and in vivo and were capable of initiating transcription in sense and antisense directions. The genome-wide correlation between in silico promoter scores and RNA polymerase binding in vitro and in vivo was higher for promoters located on the antisense strands of the genes, however, sense promoters within the uxuR gene were more active. Both regulatory RNAs synthesised from the divergent promoters inhibited expression of genes associated with the E. coli motility and chemotaxis independent of a carbon source on which bacteria had been grown. Direct effects of these RNAs were confirmed for the fliA gene encoding σ28 subunit of RNA polymerase. In addition to intracellular sRNAs, promoters located within the uxuR gene could initiate synthesis of transcripts found in the fraction of RNAs secreted in the extracellular medium. Their profile was also carbon-independent suggesting that intragenic uxuR transcripts have a specific regulatory role not directly related to the function of the protein in which gene they are encoded.

Unusual Pipistrelle: Taxonomic Position of the Malayan Noctule (Pipistrellus stenopterus; Vespertilionidae; Chiroptera).

Sergei V. Kruskop, Evgeniya N. Solovyeva, and Anna D. Kaznadzey (2018) Despite huge progress in the systematics of bats and, in particular, of the Vespertilionidae family in latest years, the taxonomic position of a number of remarkable bat species has been uncertain until now, partly because of limits in acceptable comparative material. Researchers have previously placed the Malayan noctule, Pipistrellus stenopterus, into Nyctalus, because of similar body shape and proportions, or into Pipistrellus, based on karyological analysis. This study reassesses Pipistrellus stenopterus using available collection material and compares it to various members of Nyctalus and Pipistrellus, as well as with some other related and similar genera, based on respective morphological and molecular genetic features. This species demonstrates vast morphological peculiarities compared to other Pipistrellus-like bats. Nonetheless, both mitochondrial and nuclear genetic markers unequivocally place it close to other Asian pipistrelles, most probably in a sister position to the "javanicus" species group. We propose establishing P. stenopterus as a separate subgenus, Alionoctula. Our results also confirm that Pipistrellus is paraphyletic in its current state, and we suggest that further studies explore its internal taxonomy and limits.