Global Rsh-dependent transcription profile of Brucella suis during stringent response unravels adaptation to nutrient starvation and cross-talk with other stress responses

International audienceBackground: In the intracellular pathogen Brucella spp., the activation of the stringent response, a global regulatorynetwork providing rapid adaptation to growth-affecting stress conditions such as nutrient deficiency, is essential forreplication in the host. A single, bi-functional enzyme Rsh catalyzes synthesis and hydrolysis of the alarmone (p)ppGpp, responsible for differential gene expression under stringent conditions.Results: cDNA microarray analysis allowed characterization of the transcriptional profiles of the B. suis 1330 wildtypeand Δrsh mutant in a minimal medium, partially mimicking the nutrient-poor intramacrophagic environment.A total of 379 genes (11.6% of the genome) were differentially expressed in a rsh-dependent manner, of which 198were up-, and 181 were down-regulated. The pleiotropic character of the response was confirmed, as the genesencoded an important number of transcriptional regulators, cell envelope proteins, stress factors, transport systems,and energy metabolism proteins. Virulence genes such as narG and sodC, respectively encoding respiratory nitratereductase and superoxide dismutase, were under the positive control of (p)ppGpp, as well as expression of thecbb3-type cytochrome c oxidase, essential for chronic murine infection. Methionine was the only amino acid whosebiosynthesis was absolutely dependent on stringent response in B. suis.Conclusions: The study illustrated the complexity of the processes involved in adaptation to nutrient starvation,and contributed to a better understanding of the correlation between stringent response and Brucella virulence.Most interestingly, it clearly indicated (p)ppGpp-dependent cross-talk between at least three stress responsesplaying a central role in Brucella adaptation to the host: nutrient, oxidative, and low-oxygen stress

Inhibition of β-carbonic anhydrases from Brucella suis with C-cinnamoyl glycosides incorporating the phenol moiety

A small series of C-glycosides containing the phenol moiety was tested for the inhibition of the β-class carbonic anhydrases (βCAs, EC 4.2.1.1) from Brucella suis. Many compounds showed activities in the micromolar or submicromolar range and excellent selectivity for pathogen CAs over human isozymes. Glycosides incorporating the 3-hydroxyphenyl moiety showed the best inhibition profile, and therefore this functionality represents lead for the development of novel anti-infectives with a new mechanism of action.Laboratorio de Estudio de Compuestos Orgánico

Brucella suis carbonic anhydrases and their inhibitors: Towards alternative antibiotics?

Carbonic anhydrases have started to emerge as new potential antibacterial targets for several pathogens. Two β-carbonic anhydrases, denominated bsCA I and bsCA II, have been isolated and characterized from the bacterial pathogen Brucella suis, the causative agent of brucellosis or Malta fever. These enzymes have been investigated in detail and a wide range of classical aromatic and heteroaromatic sulfonamides as well as carbohydrate-based compounds have been found to inhibit selectively and efficiently Brucella suis carbonic anhydrases. Inhibition of these metalloenzymes constitutes a novel approach for the potential development of new anti-Brucella agents. This review aims at discussing the recent literature on this topic

Role of the Brucella suis Lipopolysaccharide O Antigen in Phagosomal Genesis and in Inhibition of Phagosome-Lysosome Fusion in Murine Macrophages

Brucella species are gram-negative, facultative intracellular bacteria that infect humans and animals. These organisms can survive and replicate within a membrane-bound compartment inside professional and nonprofessional phagocytic cells. Inhibition of phagosome-lysosome fusion has been proposed as a mechanism for intracellular survival in both cell types. However, the molecular mechanisms and the microbial factors involved are poorly understood. Smooth lipopolysaccharide (LPS) of Brucella has been reported to be an important virulence factor, although its precise role in pathogenesis is not yet clear. In this study, we show that the LPS O side chain is involved in inhibition of the early fusion between Brucella suis-containing phagosomes and lysosomes in murine macrophages. In contrast, the phagosomes containing rough mutants, which fail to express the O antigen, rapidly fuse with lysosomes. In addition, we show that rough mutants do not enter host cells by using lipid rafts, contrary to smooth strains. Thus, we propose that the LPS O chain might be a major factor that governs the early behavior of bacteria inside macrophages

Oxo- and thiooxo-imidazo[1,5-c]pyrimidine molecule library: Beyond their interest in inhibition of Brucella suis histidinol dehydrogenase, a powerful protection tool in the synthesis of histidine analogues

International audienceHistidinol dehydrogenase (HDH) has been established as a virulence factor for the human pathogen bacterium Brucella suis. Targeting such a virulence factor is a relevant anti-infectious approach as it could decrease the frequency of antibiotic resistance appearance. In this paper, we describe the synthesis of a family of oxo- and thioxo-imidazo[1,5-c]pyrimidines, potential enzyme inhibitors. Beyond their anti-HDH activity, the synthesis approach of these molecules, never described before, is highly original and these oxo- and thioxo- derivatives can improve dramatically the efficiency of the histidine protection pathway for the synthesis of histidine analogues

The intramacrophagic environment of Brucella suis and bacterial response

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