PARTICIPATION OF THE TYPE VI SECRETION SYSTEM IN THE ENDOPHYTIC COLONIZATION OF PHOSPHATE SOLUBILIZING BACTERIA.

CINTHIA TAMARA LUCERO (1), GRACIELA SUSANA LORDA (1), LILIANA MERCEDES LUDUEÑA (2), FIORELA NIEVAS (3), PABLO CESAR BOGINO (3), JORGE ANGELINI (2), TANIA TAURIAN (2).

Congreso; XXX Reunión Latinoamericana de rizobiología y 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, there is the type VI secretion system (T6SS), which 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. In this study, it was evaluated whether the T6SS of a native peanut bacterium with phosphate solubilizing capacity is involved in endophytic colonization in said legume. Enterobacter sp. J49 strain was used which stands out for solubilizing significant amounts of phosphate and promoting the growth of peanut, corn and soybean plants. Initially, an in silico search was carried out in the genome of the Enterobacter sp. J49 strain for genes related to T6SS. It was possible to identify all the tss genes, with the exception of the tssE gene. Subsequently, a mutant of the Enterobacter sp. J49 strain was obtained by directed mutagenesis of one of the essential genes of the secretion system. Then, the Enterobacter sp. J49 ∆hcp strain obtained was analyzed for its colonization capacity by inoculating peanut plants. 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 promote other mechanisms involved in it.