The Bradyrhizobium Sp. LmicA16 Type VI Secretion System Is Required for Efficient Nodulation of Lupinus Spp.

Abstract

Many bacteria of the genus Bradyrhizobium are capable of inducing nodules in legumes. In this work, the importance of a type VI secretion system (T6SS) in a symbiotic strain of the genus Bradyrhizobium is described. T6SS of Bradyrhizobium sp. LmicA16 (A16) is necessary for efficient nodulation with Lupinus micranthus and L. angustifolius. A mutant in the gene vgrG, coding for a component of the T6SS nanostructure, induced less nodules and smaller plants than the wild type strain (wt) and was less competitive when coinoculated with the wt strain. A16 T6SS genes are organized in a 26 kb DNA region in two divergent gene clusters of nine genes each. One of these genes codes for a protein (Tsb1) of unknown function but containing a methyltransferase domain. A tsb1 mutant showed an intermediate symbiotic phenotype regarding vgrG mutant and higher mucoidy and motility than the wt strain in free living conditions. T6SS promoter fusions to the lacZ reporter indicate expression in nodules but not in free living cells grown in different media and conditions. The analysis of nodule structure revealed that the level of nodule colonization was significantly reduced in the mutants with respect to the wt strain.

Sporulation Activated via σ W Protects Bacillus from a Tse1 Peptidoglycan Hydrolase Type VI Secretion System Effector

“…(B) Phylogenetic distribution of T6SS clusters in five main groups based on the tssB locus. Phylogenetic analysis was done using previous nomenclature ( 107 , 108 ) based on the core protein TssB, widely used as structural component for T6SS phylogenetic analysis ( 33 , 109 ). The maximum-likelihood method with 1,000 bootstrap replicates was built with Mega X ( 110 ) using Clustal Omega ( 97 ).…”

Correlating phylogenetic and functional diversity of thenod-free but nodulatingBradyrhizobiumphylogroup

“…However, it is still interesting to note that as an intermediate clade, the two strains in Clade 2 uniquely have a gene cluster for the type VI secretion system (T6SS) (Fig. S5, Dataset S5), which is known to influence bacterial competitiveness and symbiosis with eukaryotes (De Sousa et al, 2023; Tighilt et al, 2022). The effects on symbiosis with plants may be closely related to the effectors secreted by T6SS that interact with the host plant and surrounding microbiota (De Sousa et al, 2023).…”

The role of the type VI secretion system in the stress resistance of plant-associated bacteria

“…BH72 (Lucero et al 2022 ), (Mosquito et al 2022 ), (Durán et al 2021 ), (Shidore et al 2012 ) Influences the symbiosis of Rhizobium and hosts R. leguminosarum RBL5523, R. etli Mim1, P. phymatum STM815, Bradyrhizobium sp. LmicA16 (Bladergroen et al 2003 ), (Salinero-Lanzarote et al 2019 ), (Hug et al 2021 ), (Tighilt et al 2022 ) …”