Participation of the type VI secretion system in the endophytic colonization of phosphate solubilizing bacteria

LUCERO, C.T; LORDA, G.S.; LUDUEÑA, L.M.; NIEVAS, F.; BOGINO, P.C.; ANGELINI, J.; TAURIAN, T.

Congreso; XXX Reunión Latinoamericana de Rizobiología - V Conferencia Latinoamericana de Microorganismos Promotores del Crecimiento Vegetal; 2021

There are different types of secretion systems in bacteria that transfer molecules both to the extracellular medium and to the interior of adjacent cells. In mutualistic endophytic bacteria, type VI secretion system (T6SS) is related to important functions, such as interbacterial competition, stress response, quorum sensing, biofilm formation and symbiosis. The endophytic population associated with different plants has a high number of genes related to T6SS, which suggests that it would play an important role in its interaction with the plant. Phosphate solubilizing bacteria constitute a group of bacteria of great relevance in the rhizosphere as they provide phosphorus to plants. Among them, those with endophytic colonization capacity have adaptive and survival advantages. The aim of this study was to analyze if the T6SS of a native peanut bacterium with phosphate solubilizing capacity is involved in its endophytic colonization in this legume. Enterobacter sp. J49 strain was used due its efficient ability to solubilize significant amounts of insoluble phosphates and to promote the growth of peanut, corn and soybean plants. Initially, an in silico analysis looking for genes related to T6SS in the genome of the Enterobacter sp. J49 strain was developed. It was possible to identify, with the exception of the tssE gene, all the tss genes in its genome. Subsequently, a mutant of the Enterobacter sp. J49 strain was obtained by interrupting one of the essential tss genes. Then, the Enterobacter sp. J49Δhcp strain obtained was inoculated on peanut plants in order to analyze its colonization capacity. The results obtained indicated a significant decrease in the epiphytic and endophytic aerial and radical colonization of the mutant with respect to the wild strain. It is possible to conclude that T6SS, although not essential, would participate in bacterial colonization, either accelerating the infection, or promoting other mechanisms involved in it.