Tam system is involved in cell envelope homeostasis in the opportunistic pathogen Ochrobactrum anthropi

ZIMMERMAN LUCIANA M.; BIALER MAGALÍ G.; SYCZ GABRIELA; RUSSO DANIELA M.; ZORREGUIETA ANGELES

Chapadmalal

Congreso; XVIII Congreso de la Sociedad Argentina de Microbiologia General SAMIGE 2023; 2023

SAMIGE

The ability of Gram-negative pathogens to resist the action of host toxic agents relies on the correct assembly of the cell envelope, particularly the outer membrane (OM). Despite the progress in elucidating the mechanisms underlying OM biogenesis, several questions remain unsolved. Our prior research demonstrated the role of the Translocation and Assembly Module (TAM) system in maintaining the integrity of the OM in Brucella suis, an intracellular pathogen belonging to the Alphaproteobacteria group. The aim of this work is to give insight into the role of the TAM system in the cell envelope biogenesis using a species belonging to the Brucella closest genus, the opportunistic pathogen Ochrobactrum anthropi. A mutant in the homologue locus of O. anthropi (Oant_0054) was generated and several cell envelope related phenotypes were analysed. The O. anthropi tamB mutant showed enhanced sensitivity to 0.5% SDS and a marked susceptibility to lysozyme. Furthermore, the O. anthropi wild type (wt) and tamB mutant strains displayed differences in minimum inhibitory concentration (MIC) for vancomycin. No differences were observed between the tamB mutant and the wt strain after Triton X-100, DOC or EDTA treatment. Transmission electron microscopy (TEM) showed some alterations in the cell envelope of the tamB mutant. While the wt strain exhibited defined OM edges, the mutant showed a looser appearance. Taken together, these results show that the cell envelope integrity of the O. anthropi TamB-defective strain is compromised. Recently, we have successfully performed subcellular fractionation of the OM and IM (inner membrane), an achievement that has not been possible in Brucella due to its cell envelope stiffness. We observed differences in the densities of both IM and OM between wt and tamB strains. These differences may indicate an altered composition of the membranes, probably in protein and/or phospholipid content.