Identification and characterization of RomA, a key factor for membrane homeostasis in Rhizobiales bacteria

E.VALGUARNERA, ; J. M. SPERA; F. GUAIMAS; M. F. FELDMAN; S. ALTABE; A C.CASABUONO,; A S. COUTO; J E. UGALDE

Indiana

Conferencia; 22nd Annual Midwest Microbial Conference; 2015

All bacteria must be capable of sensing environmental changes in order to adapt to the multiplicity of changes and fluctuations generated in the environment. Cell membranes have a multiple role both in the detection and response to environmental stimuli, as well as in the protection of the bacterial cell against threats or injuries from the external medium. Balance between both functions requires a topological organization of membrane components, in particular, protein macromolecular complexes of diverse function. The present work describes the identification and characterization of a gene (romA), restricted to alpha-proteobacteria, whose protein product has a periplasmic localization and is weakly bound to membranes. In Brucella, the absence of RomA affects membrane lipid composition as well as the ratio between smooth and rough LPS molecules. The romA mutant in Brucella shows a diminished in vitro infectivity, but surprisingly, generates an in vivo hipervirulent phenotype. Additionally, the absence of RomA generates alterations in the subcellular distribution of membrane protein complexes. In Agrobacterium, RomA is also necessary for the maintenance of membrane homeostasis, as the mutant strain shows reduced motility as the consequence of an improper assembly of the bacterial flagellum. Our results demonstrate a general role for RomA as a key factor in membrane homeostasis by regulating the architecture of membrane macromolecular complexes both in Brucella and Agrobacterium, showing specific functions depending on the evolutionary niche and phenotypical traits of each microorganism