Characterization of an endophytic bacterium (Pseudomonas aeruginosa), originating from tomato (Solanum lycopersicum L.), and its ability to inhabit the parasitic weed Phelipanche aegyptiaca.

PHELIPANCHE AEGYPTIACA: is an obligate holo-parasitic weedlacking a functional photosynthetic system, which subsists on roots of a wide range of host crops, causing severe losses in yield quality and quantity. The parasite and its host are connected through their vascular system, forming a unique ecological system that enables the exchange of various substances. In a previous study, it was suggested that endophytic bacteria, which naturally inhabit the internal tissues of plants, can also be transmitted from the parasitic weed to its host and vice versa. In the current study, we investigate the characteristics of a previously isolated Pseudomonas sp. PhelS10 strain using both biochemical and molecular methods. This isolate was obtained from tomato plant tissue and was able to reduce P. aegyptiaca parasitism, and thus it may serve as a biocontrol agent. Our results revealed that production of Pseudomonas aeruginosa quinolone signal (PQS) was 2.1 times higher than that of the standard Pseudomonas aeruginosa strain (PAO1), which contributed to a 22% higher biofilm formation capability. PhelS10 strain was detected in the xylem of tomato plants using FISH analysis. In addition, PhelS10 strain was found in the parasitic weed's inner tissues, confirming the hypothesis that endophytic bacteria traffic between the host plant and its parasitic weed.

Structural Insights into Curli CsgA Cross-ß Fibril Architecture Inspire Repurposing of Anti-amyloid Compounds as Anti-biofilm Agents.

Curli amyloid fibrils secreted by Enterobacteriaceae mediate host cell adhesion and contribute to biofilm formation, thereby promoting bacterial resistance to environmental stressors. Here, we present crystal structures of amyloid-forming segments from the major curli subunit, CsgA, revealing steric zipper fibrils of tightly mated ß-sheets, demonstrating a structural link between curli and human pathological amyloids. D-enantiomeric peptides, originally developed to interfere with Alzheimer's disease-associated amyloid-ß, inhibited CsgA fibrillation and reduced biofilm formation in Salmonella typhimurium. Moreover, as previously shown, CsgA fibrils cross-seeded fibrillation of amyloid-ß, providing support for the proposed structural resemblance and potential for cross-species amyloid interactions. The presented findings provide structural insights into amyloidogenic regions important for curli formation, suggest a novel strategy for disrupting amyloid-structured biofilms, and hypothesize on the formation of self-propagating prion-like species originating from a microbial source that could influence neurodegenerative diseases.

Frateuria defendens sp. nov., bacterium isolated from the yellows grapevine's disease vector Hyalesthes obsoletus.

A Dyella-like bacterium was previously isolated from the planthopper Hyalesthes obsoletus (Hemiptera). Based on its 16S rRNA gene sequence, strain DHoT was assigned to the family Rhodanobacteraceae with Dyella and Frateuria as its closest relatives. The closest 16S rRNA gene sequences were Frateuria aurantia DSM 6220T (98.2 %), Dyella thiooxydans ATSB10T (98 %), Dyella terrae JS14-6T (97.8 %) and Dyella marensis CS5-B2T (97.8 %). Strain DHoT is a Gram-negative, aerobic, motile, yellow-pigmented, rod-shaped bacterium. Strain DHoT cells grew well at 28-30 °C and at pH 6.5-7.5 on a nutrient agar plate. DNA-DNA hybridization showed that the relatedness between strain DHoT and D. jiangningensis strain SBZ3-12T, and F. aurantia DSM 6220T was 42.7 and 42.6 %, respectively. Ubiquinone Q-8 was the predominant respiratory quinone, and the major fatty acids (>10 %) were iso-C15 : 0, iso-C16 : 0 and iso-C17 : 0. In silico analysis based on phylogenetics and sequence identity at the nucleotide and protein levels suggests that Frateuria is the closest known relative of strain DHoT. Based on the phenotypic, chemotaxonomic and phylogenetic data, strain DHoT was designated as a novel species of the genus Frateuria, for which the name Frateuria defendens sp. nov. is proposed. The type strain is DHoT (=NCCB 100648T; =DLBT=DSM 106169T).

Introduction of a putative biocontrol agent into a range of phytoplasma- and liberibacter-susceptible crop plants.

BACKGROUND: Phytoplasma, the causative agent of Bois Noir disease of grapevines, are vectored by the planthopper Hyalesthes obsoletus (Hemiptera: Cixiidae). A Dyella-like bacterium (DLB) isolated from H. obsoletus inhibits the growth of Spiroplasma melliferum, a cultivable relative of phytoplasma. Additional evidence suggests that DLB can reduce the symptoms of yellows disease in grapevine plantlets. The aim of this study was to test whether DLB could colonize a range of phytoplasma- and liberibacter-sensitive crop plants, and thus assess its potential agricultural use. RESULTS: Vitex agnus-castus, the preferred host plant of H. obsoletus was found to be a natural host of DLB, which was successfully introduced into a range of crop plants belonging to seven families. The most effective DLB application method was foliar spraying. Microscopy observation revealed that DLB aggregated on the leaf surface and around the stomata, suggesting that this is its route of entry. DLB was also present in the vascular tissues of plants, indicating that it moved systemically through the plant. CONCLUSIONS: DLB is a potential biocontrol agent and its broad spectrum of host plants indicates the possibility of its future use against a range of diseases caused by phloem-limited bacteria. © 2017 Society of Chemical Industry.