"Effects of light on the non-photosynthetic plant growth promoting rhizobacteria A. brasilense Az39?

MOLINA, ROMINA; NIEVAS SOFIA; CONIGLIO, ANAHÍ; MORA, M VERONICA; ROSAS, SUSANA; CASSAN, FABRICIO D.

Simposio; Symposium at the 19th Congress of the European Society for Photobiology; 2021

With the discovery of photoreceptors in prokaryotes, progress was made in the understanding of their functionality in non-photosynthetic bacteria1. A. brasilense Az39 is a non-photosynthetic rhizobacterium used as a biofertilizer in South America during the last 40 years. In our laboratory, we analyzed the Az39 genome, generated mutants at the level of its photoreceptors, and studied its physiological and microbiological responses to white, blue and red light (PAR38) under different experimental systems. In a complementary way, we analyzed its physiological behavior in soybean leaves inoculated with this bacterium and exposed to different light conditions. Our results allowed us to understand that the tolerance of Az39 to light depends on the culture conditions. In particularly, under conditions of gregarious growth (culture on solid medium), white and blue light were found to be lethal for this bacterium; however, positive effects were observed under liquid culture conditions, at level of the phytohormones production and lifestyle characters. The survival of these bacteria on soybean leaves was drastically affected by the exposure to all light sources after inoculation, but mostly by white light on bacterial phytochrome expression deficient strain. Summarizing, A. brasilense Az39 is differentially affected by light conditions in both positive and negative ways, and this capacity is dependent on the bacterial growth conditions.