Circadian variation in Pseudomonas fluorescens (CHA0)-mediated paralysis of Caenorhabditis elegans

ROMANOWSKI, A; MIGLIORI, ML; VALVERDE, C; GOLOMBEK, DA

MICROBIAL PATHOGENESIS

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 2010 vol. 50 p. 23 - 30

0882-4010

Abiotic and biotic environmental stressors play a key role in the ecophysiology of most organisms. As the presence and activity of stress-inducing agents vary along the day, organisms that are able to predict these periodic changes are better fit to survive. C. elegans, a soil dwelling nematode, is subjected to daily changes in its natural environment, and its tolerance to osmotic and oxidative stress varies along the day. Pseudomonas fluorescens strain CHA0 is a soil bacterium that produces a set of secondary metabolites that serve to antagonize phytopathogenic fungi and therefore to promote healthy growth of several plant species. Here we show that strain CHA0 is able to affect C. elegans either under growth limiting conditions (i.e., slow killing) or by rapid paralysis in nutrient replete conditions (fast killing). Both types of toxicity require the posttranscriptional Gac/Rsm regulatory cascade, and the fast paralytic killing depends strongly on hydrogen cyanide production. The response observed in C. elegans nematodes to fast paralytic killing varies along the day and its sensitivity is higher during the night, at ZT12 (lights off). This behavior correlates well with HCN tolerance, which is higher during the day, at ZT0 (lights on). This innate immune response to P. fluorescens CHA0 might depend on the stress response pathway of C. elegans. The fact that the tolerance varies daily gives further proof of an underlying clock that governs cyclic behavior in C. elegans.