Abstract
Brucella species cause brucellosis, a worldwide extended zoonosis. The brucellae are related to free-living and plant-associated α2-Proteobacteria and, since they multiply within host cells, their metabolism probably reflects this adaptation. To investigate this, we used the rodent-associated Brucella suis biovar 5, which in contrast to the ruminant-associated Brucella abortus and Brucella melitensis and other B. suis biovars, is fast-growing and conserves the ancestral Entner-Doudoroff pathway (EDP) present in the plant-associated relatives. We constructed mutants in Edd (glucose-6-phosphate dehydratase; first EDP step), PpdK (pyruvate phosphate dikinase; phosphoenolpyruvate ⇌ pyruvate), and Pyk (pyruvate kinase; phosphoenolpyruvate → pyruvate). In a chemically defined medium with glucose as the only C source, the Edd mutant showed reduced growth rates and the triple Edd-PpdK-Pyk mutant did not grow. Moreover, the triple mutant was also unable to grow on ribose or xylose. Therefore, B. suis biovar 5 sugar catabolism proceeds through both the Pentose Phosphate shunt and EDP, and EDP absence and exclusive use of the shunt could explain at least in part the comparatively reduced growth rates of B. melitensis and B. abortus. The triple Edd-PpdK-Pyk mutant was not attenuated in mice. Thus, although an anabolic use is likely, this suggests that hexose/pentose catabolism to pyruvate is not essential for B. suis biovar 5 multiplication within host cells, a hypothesis consistent with the lack of classical glycolysis in all Brucella species and of EDP in B. melitensis and B. abortus. These results and those of previous works suggest that within cells, the brucellae use mostly 3 and 4 C substrates fed into anaplerotic pathways and only a limited supply of 5 and 6 C sugars, thus favoring the EDP loss observed in some species.
Highlights
Members of the genus Brucella are α2-Proteobacteria that infect a wide range of vertebrates causing brucellosis in mammals (Al Dahouk et al, 2008; Whatmore, 2009; Soler-Lloréns et al, 2016), a zoonosis with a high impact on developing countries worldwide (McDermott et al, 2013)
As that hypothesis can be tested by blocking pyruvate synthesis at other levels of the central C pathways, in this work we applied this approach by deleting edd in B. suis biovar 5 and, instead of gnd, the genes putatively coding for pyruvate phosphate dikinase and pyruvate kinase (Figure 1)
The B. suis 513 enzymes involved in PEP-pyruvate conversions would be a pyruvate phosphate dikinase (PpdK) and a pyruvate kinase (Pyk) (Figure 1)
Summary
Members of the genus Brucella are α2-Proteobacteria that infect a wide range of vertebrates causing brucellosis in mammals (Al Dahouk et al, 2008; Whatmore, 2009; Soler-Lloréns et al, 2016), a zoonosis with a high impact on developing countries worldwide (McDermott et al, 2013). Since they are facultative intracellular pathogens unable to persist in nature outside their hosts, this origin implies that they have probably adapted their metabolism to the peculiarities of the Brucella containing vacuoles (BCV) where they multiply Because of their early identification and greater impact on domestic livestock and humans, metabolism has been investigated almost exclusively in B. abortus, B. melitensis, and biovars 1 and 3 of B. suis. B. abortus, B. melitensis, and B. suis other than biovar 5 rely exclusively on PPP because all carry a disabling mutation in edd This shows the dispensability of EDD in the spp. that cause disease in livestock and, consistent with the lack of the phosphofructokinase of the Embden-Meyerhof-Parnas (classical glycolysis) in all brucellae (Barbier et al, 2018), supports the hypothesis that glucose fueling into TCA is not essential in BCVs and was lost in some clades. We present experiments that confirm the corresponding predicted metabolic phenotypes as well as the results of an assessment of virulence in the mouse model of brucellosis
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
