Characterization of FliL Proteins in Bradyrhizobium diazoefficiens : Lateral FliL Supports Swimming Motility, and Subpolar FliL Modulates the Lateral Flagellar System

MENGUCCI, FLORENCIA; DARDIS, CAROLINA; MONGIARDINI, ELÍAS J.; ALTHABEGOITI, MARÍA J.; PARTRIDGE, JONATHAN D.; KOJIMA, SEIJI; HOMMA, MICHIO; QUELAS, JUAN I.; LODEIRO, ANÍBAL R.

JOURNAL OF BACTERIOLOGY

AMER SOC MICROBIOLOGY

Lugar: Washington; Año: 2020 vol. 202

0021-9193

Bradyrhizobium diazoefficiens is a soil alphaproteobacterium that possessestwo evolutionarily distinct flagellar systems, a constitutive subpolar flagellumand inducible lateral flagella that, depending on the carbon source, may be expressedsimultaneously in liquid medium and used interactively for swimming. Ineach system, more than 30 genes encode the flagellar proteins, most of which arewell characterized. Among the exceptions is FliL, which has been scarcely studied inalphaproteobacteria and whose function in other bacterial classes is somewhat controversial.Because each B. diazoefficiens flagellar system contains its own fliL paralog,we obtained the respective deletions ΔfliLS (subpolar) and ΔfliLL (lateral) to studytheir functions in swimming. We determined that FliLL was essential for lateralflagellum-driven motility. FliLS was dispensable for swimming in either liquid orsemisolid medium; however, it was found to play a crucial role in upregulation ofthe lateral flagellum regulon under conditions of increased viscosity/flagellar load.Therefore, although FliLS seems to be not essential for swimming, it may participatein a mechanosensor complex that controls lateral flagellum induction