The mglA gene and its flanking regions in Brucella: The role of mglA in tolerance to hostile environments, Fe-metabolism and in vivo persistence

Abstract

We previously demonstrated that a spontaneous smooth small-colony variant of Brucella abortus S19 is characterized by increased in vivo persistence and the differential expression of a gene predicted to encode a galactoside transport ATP binding protein (mglA). In order to further investigate the role of this gene in the context of its flanking regions, we analyzed the respective DNA sequences from the formerly described B. abortus S19 as well as from avirulent B. neotomae 5K33 and compared these with published data from other Brucella species. Deletion mutagenesis of mglA in the large-colony variant of B. abortus S19 resulted in increased tolerance of the deletion mutant to a hyperosmotic (toxic), galactose-containing medium as well as to oxidative stress (H 2 O 2 ). Whilst the deletion mutant is characterized by reduced growth on solid Fe 3+ -containing minimal medium (small-colony morphology), in vivo studies in mice demonstrated statistical significant differences in the bacterial load of spleens in the pre-immune, but not in the late phase of the infection.

Survival of Brucella abortus S19 and other Brucella spp. in the presence of oxidative stress and within macrophages

“…The hypothesis was that high tolerance against oxidative stress as shown most impressively for B. neotomae may positively correlate with the degree of growth and survival in macrophages. The results presented here extend previous findings (Jacob et al 2012 ), i.e., that the B. abortus ∆mglA mutant strain (being more tolerant to H 2 O 2 ) was found in up to 10-fold higher amounts in macrophages when compared to the parental strain B. abortus S19 at 24 h and 48 h after infection in the presence or absence of any preincubation of the macrophages with iron (Fig. 6 ).…”

“…In a previous paper investigating the effect of a depletion of the mglA gene (Jacob et al 2006 , 2012 , 2016 ), we demonstrated that the mgl-operon may be an interesting gene region to increase safety and efficacy of the available vaccine strain Brucella abortus S19 . The mutant was characterized by (a) decreased growth on an iron (Fe 2+ )-containing minimal basic medium (Jacob et al 2012 ), (b) an increased tolerance against oxidative stress (H 2 O 2 ), (c) an increased fitness in CRL2471 macrophages, and (d) a significant expression of TNFα, IL1, and IL6 cytokines in CRL2471 macrophages (Jacob et al 2016 ).…”

“…B. abortus ∆mglA 3.14 (Jacob et al 2012 ), B. microti CCM4915 (Hubálek et al 2008 ; Audic et al 2009 ; Jiménez de Bagues et al 2010 ), B. abortus S19 (Crasta et al 2008 ), B. neotomae 5K33 (Stoenner and Lackmann 1957 ), as well as Brucella 83/13 (Tiller et al 2010a , b ; Jiménez de Bagues et al 2014 ) were grown in tryptic soy broth (TSB) and subsequently stored at − 80 °C as previously described (Hort et al 2003 ). B. neotomae 5K33 and B. microti CCM4915 were obtained from Dr. Garin-Bastuji, B., AFFSA (Maison-Alfort, France).…”

“…In a previous paper, we showed that an isogenic ∆ mglA deletion mutant of B. abortus S19 shows an increased tolerance to H 2 O 2 and survival inside of macrophages but was found to be inhibited by Fe 2+ in a minimal medium (Jacob et al 2012 ).…”

“…Gene mglA is located in chromosome II of B. abortus and has recently been associated with stress responses and detoxification (Jacob et al 2012 , 2016 ). Close to mglA (a various polyols ABC transporter, ATP binding component, http://pubseed.theseed.org/?page=CompareMetabolicReconstruction&organism=430066.4 ), various other stress response genes are located.…”