Rol of light on the physiological characteristics of Ralstonia solanacearum in the colonization of host plants

TANO, JOSEFINA; PETROCELLI, SILVANA; TONDO, MARÍA LAURA; CARRAU, ANALÍA; ORELLANO, ELENA G.

Villa Carlos Paz

Congreso; XIII ENCUENTRO LATINOAMERICANO DE FOTOQUÍMICA Y FOTOBIOLOGÍA; 2017

Comité Latinoamericano de Fotoquímica y Fotobiología

Light perception is achieved by photoreceptor proteins, which trigger the signal transduction cascades that regulate the light responses. LOV (Light, Oxygen or Voltage) photoreceptors are flavin-binding proteins using flavin mononucleotide (FMN) as chromophore [1-2]. Ralstonia solanacearum GMI1000 is a phytopatogen responsible of bacterial wilt in different crops of great agronomic importance such as potato and tomato [3]. In the Rso genome there are one gene encoding a putative transmembrane LOV protein: rsp0254 [4]. The aim of this work was to study the role of LOV photoreceptor in the bacterial physiology.We evaluated the bacterial growth of Rso GMI1000 in liquid medium in white light, blue light and darkness. Several physiological parameters involved in the virulence of Rso related to the first stages of infections in the host plant were determined in the different light conditions. First, bacterial displacement mechanisms such as swimming and twitching, and the production of biosurfactants were analyzed. We also studied characteristics related to the bacterial colonization inside the host plant, such as type two secretion system (TTSS) and oxidative stress. The results obtained revealed that the white light affect the bacterial growth. It was observed that white light inhibits swimming and twitching motility. Regarding the production of biosurfactants, the strain presented the same emulsification capacity in kerosene and sunflower oil in all light conditions, however, the emulsification layer in sunflower oil of cultures grown in blue light, presented a greater stability over time (about one month), indicating that, in this condition, the strain produces a different biosurfactant from that of other light conditions. Finally, no differences were observed in the production of hydrolytic enzymes, but we have significant differences with respect to oxidative stress in white light, blue light and darkness. These results demonstrate that the rsp0254 gene of Rso GMI1000 is functional and would be involved in the regulation of bacterial physiology.