Adhesive Functions or Pseudogenization of Type Va Autotransporters in Brucella Species

Abstract

Adhesion to host cells is a key step for successful infection of many bacterial pathogens and may define tropism to different host tissues. To do so, bacteria display adhesins on their surfaces. Brucella is an intracellular pathogen capable of proliferating in a wide variety of cell types. It has been described that BmaC, a large protein that belongs to the classical (type Va) autotransporter family, is required for efficient adhesion of Brucella suis strain 1330 to epithelial cells and fibronectin. Here we show that B. suis 1330 harbors two other type Va autotransporters (BmaA and BmaB), which, although much smaller, share significant sequence similarities with BmaC and contain the essential domains to mediate proper protein translocation to the bacterial surface. Gain and loss of function studies indicated that BmaA, BmaB, and BmaC contribute, to a greater or lesser degree, to adhesion of B. suis 1330 to different cells such as synovial fibroblasts, osteoblasts, trophoblasts, and polarized epithelial cells as well as to extracellular matrix components. It was previously shown that BmaC localizes to a single bacterial pole. Interestingly, we observed here that, similar to BmaC, the BmaB adhesin is localized mostly at a single cell pole, reinforcing the hypothesis that Brucella displays an adhesive pole. Although Brucella species have strikingly similar genomes, they clearly differ in their host preferences. Mainly, the differences identified between species appear to be at loci encoding surface proteins. A careful in silico analysis of the putative type Va autotransporter orthologues from several Brucella strains showed that the bmaB locus from Brucella abortus and both, the bmaA and bmaC loci from Brucella melitensis are pseudogenes in all strains analyzed. Results reported here evidence that all three autotransporters play a role in the adhesion properties of B. suis 1330. However, Brucella spp. exhibit extensive variations in the repertoire of functional adhesins of the classical autotransporter family that can be displayed on the bacterial surface, making them an interesting target for future studies on host preference and tropism.

Kinetics of Placental Infection by Different Smooth Brucella Strains in Mice

“…While Brucella internalisation has been widely studied in macrophages and epithelial cells [ 39 , 40 , 41 ], adhesion and the internalisation mechanism in trophoblast cells requires further clarification. Recently, two proteins of B. suis bv1 1330 (BmaA and BmaB) have been described as feasible adhesins involved in trophoblast adhesion process [ 42 ]. Although Brucella strains share a high degree of genome similarity [ 43 ], bmaA and bmaB loci seem to correspond to pseudogenes in B. melitensis [ 42 ].…”

“…Recently, two proteins of B. suis bv1 1330 (BmaA and BmaB) have been described as feasible adhesins involved in trophoblast adhesion process [ 42 ]. Although Brucella strains share a high degree of genome similarity [ 43 ], bmaA and bmaB loci seem to correspond to pseudogenes in B. melitensis [ 42 ]. Accordingly, variations in the functional adhesins between Brucella species have been related with host preferences [ 44 ]; this fact could explain different adhesion and internalisation ratios between B. melitensis and B. suis bv2 observed in this study.…”

Cross regulation in a three-component cell envelope stress signaling system ofBrucella

“…For example, EssR binds to the promoter of BOV_0115 (Omp25d), which contributes to cell envelope integrity (64, 65), and B. ovis -host interaction (66). The outer membrane autotransporters, bmaA and bmaC , which are important for protein translocation to the cell surface (67) and for host cell adherence (11) are also bound by CenR/EssR but do not change in expression upon cenR or essRS deletion. Additional studies are necessary to determine what CenR/EssR-bound or regulated genes determine B. ovis cell size and support B. ovis fitness under envelope stress and in the intracellular niche.…”

Membrane Protein Bcest Is Involved in Hyphal Growth, Virulence and Stress Tolerance of Botrytis cinerea

“…Among them, adhesin Ata is an important virulence factor that can promote the formation of bacterial bio lms (Weidensdorfer et al 2019). BmaC can facilitate attachment between bacteria and hosts (Bialer et al 2021).…”