TAM SYSTEM IS INVOLVED IN PERMEABILITY IN Α-PROTEOBACTERIA

BIALER MAGALÍ; ZORREGUIETA, ANGELES; ZIMMERMAN , LUCIANA; RUSSO, DANIELA MARTA; SYCZ, GABRIELA

mendoza

Congreso; SAIB; 2022

The ability of Gram-negative pathogens to survive and invade host cells depends on the correct assembly of the cell envelope,especially the outer membrane (OM). Our previous work showed that the TAM (Translocation and Assembly Module) system isrequired for the integrity of OM of Brucella suis, an intracellular pathogen that belongs to the Alphaproteobacteria group. The aimof this work is to give insight into the role of the TAM system in the cell envelope biogenesis of Alphaproteobacteria plylum, usingas model bacterium the opportunistic pathogen Ochrobactrum anthropi. A mutant in the tamB homologue locus of O. anthropi(Oant_0054) was generated and several cell envelope related phenotypes were analyzed. While some phenotypes were similar tothose of the Brucella tamB mutant, others were different. The O. anthropi tamB mutant showed enhanced sensitivity to SDS 0.5%and a marked susceptibility to lysozyme. However, no differences were detected between the tamB mutant and the wild type (wt)strain after Triton X-100, DOC or EDTA treatment. Surprisingly, while the Brucella tamB mutant had shown a marked sensitivityto polymyxin B, the O. anthropi mutant was even more resistance to polymyxin B compared to the wt and the complemented strain.Moreover, transmission electron microscopy (TEM) was performed in both strains and showed different structural characteristicsof the membrane. While the wild-type strain exhibited defined edges of the OM, the mutant had a looser appearance. Takentogether, these results show that while it is clear that the TAM system is crucial for the cell envelope biogenesis and homeostasisin Alphaproteobacteria, the impact of the absence of a functional TAM system depends on the characteristics of the cell envelopeof each species, and in particular to those of the OM.