Pseudomonas fortuita sp. nov., isolated from the endosphere of a wild yam.

A Gram-negative, strictly aerobic bacterial strain was isolated from asymptomatic leaf tissue of a wild yam plant. Optimal growth was observed at 28 °C and pH 7, and catalase and oxidase activities were detected. Polyphasic taxonomic and comparative genomics revealed that strain LMG 33091T represents a novel species of Pseudomonas. The nearest phylogenetic neighbours of strain LMG 33091T were Pseudomonas putida NBRC 14164T (with 99.79 % 16S rRNA sequence identity), Pseudomonas alkylphenolica KL28T (99.28 %) and Pseudomonas asplenii (99.07 %) ATCC 23835T. MALDI-TOF MS analysis yielded distinct profiles for strain LMG 33091T and the nearest phylogenetic neighbours. Average nucleotide identity analyses between the whole genome sequence of strain LMG 33091T and of the type strains of its nearest-neighbour taxa yielded values below the species delineation threshold and thus confirmed that the strain represented a novel Pseudomonas species, for which we propose the name Pseudomonas fortuita sp. nov., with strain LMG 33091T (=GMI12077T= CFBP 9143T) as the type strain.

Structures of the P. aeruginosa FleQ-FleN master regulators reveal large-scale conformational switching in motility and biofilm control.

Pseudomonas aeruginosa can cause a wide array of chronic and acute infections associated with its ability to rapidly switch between planktonic, biofilm, and dispersed lifestyles, each with a specific arsenal for bacterial survival and virulence. At the cellular level, many of the physiological transitions are orchestrated by the intracellular second messenger c-di-GMP and its receptor-effector FleQ. A bacterial enhancer binding protein, FleQ acts as a master regulator of both flagellar motility and adherence factor secretion and uses remarkably different transcription activation mechanisms depending on its dinucleotide loading state, adenosine triphosphatase (ATPase) activity, interactions with polymerase sigma (σ) factors, and complexation with a second ATPase, FleN. How the FleQ-FleN tandem can exert diverse effects through recognition of a conserved FleQ binding consensus has remained enigmatic. Here, we provide cryogenic electron microscopy (cryo-EM) structures of both c-di-GMP-bound and c-di-GMP-free FleQ-FleN complexes which deepen our understanding of the proteins' (di)nucleotide-dependent conformational switching and fine-tuned roles in gene expression regulation.