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Intracellular survival of B. abortus BAM41 (open bars) and 2308 (filled bars) in J774 murine macrophages. Bacteria were recovered from the macrophages at different times after infection and intracellular live brucellae were determined by a c.f.u. count on BA plates.
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Brucella abortus is known to produce 2,3-dihydroxybenzoate (2,3-DHBA) and to use this catechol as a siderophore to grow under iron-limited conditions. In this study a mutant (BAM41) is described that is deficient in siderophore production by insertion of Tn5 in the virulent B. abortus strain 2308. This mutant was unable to grow on iron-deprived med...
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... of this catechol could provide intracellular brucellae with an efficient mechanism for acquiring iron in an iron- restricted environment that exists within the phagosome, thereby contributing to bacterial proliferation in the host. However, a recent report indicated that production of 2,3-DHBA was not required for rep- lication of Brucella in murine macrophages or for the establishment of a chronic infection in the BALB \ c mouse model (Bellaire et al ., 1999). In this work we report the isolation and characterization of a mutant B . abortus strain which, unlike the parental strain, was siderophore-negative in chrome-azurol-S (CAS) plates and unable to grow in iron-restricted medium, although it secreted 2,3-DHBA. The growth restriction observed under these conditions was over- come by the addition of iron in a soluble form or of a catecholic extract from culture supernatants of the parental strain grown in the presence of subinhibitory concentrations of EDDA. The mutant strain altered in siderophore production was deficient in iron assimilation but did multiply in macrophages. A bank of B . abortus 2308 Tn 5 insertion mutants was grown in MMB agar and tested for siderophore secretion. Isolated colonies were deposited on modified CAS plates. Although B . abortus was unable to grow on this medium, the siderophore present in the sample was able to decolorize CAS. The presence of a siderophore was considered positive when an orange halo was present under the mass of bacteria. Three hundred colonies were assayed by this method. The orange halo was absent in one isolate which was named BAM41 (Fig. 1). To assess the ability of the CAS-negative mutant BAM41 to grow in media with low availability of iron we tested the parental and the mutant strains in liquid MMB containing different concentrations of EDDA. The results showed that at EDDA concentrations higher than 15 μ M the biomass of the mutant strain was considerably lower than that of the parental strain (Fig. 2). This result suggested that the mutant BAM41 was unable to assimilate iron when the metal was chelated by EDDA. Addition of Fe(III) in the form of NTA Fe(III) reverted the inhibitory effect of EDDA on strain BAM41, demonstrating that the inhibition was caused by the absence of bioavailable iron in the medium (Fig. 2) Supernatants from B . abortus cultures grown in MMB medium containing a subinhibitory concentration of EDDA were analysed by the Arnow test for catechol content at different time points. Maximal production of catechols was observed at the beginning of the stationary phase of growth. The amount of catechol detected for a particular strain under the same culture conditions varied considerably between different assays. However, when catechol was detected, the amount found was always proportional to the biomass of bacterial cells present in iron-limited cultures. Catechols were extracted from supernatants with ethyl acetate, concentrated and analysed by TLC. This analysis indicated the presence of a catechol molecule (Arnow-positive) with an R identical to that of 2,3- f DHBA both in the mutant BAM41 and in the parental strain, 2308. Strain 2308 presented, in addition, a second Arnow-positive spot that exhibited a lower R and was f less abundant than 2,3-DHBA (Fig. 3). To confirm that the fast-migrating catechol described above was 2,3-DHBA we performed a cross-feed assay with the E . coli entA mutant AN193, unable to synthesize 2,3-DHBA, and hence enterochelin. This strain cannot grow in media with inhibitory concentrations of a strong iron chelator, such as DIP, unless 2,3- DHBA is present. The results showed that filtered supernatants from both B . abortus 2308 and mutant BAM41, were able to cross-feed the E . coli entA mutant, indicating that they contained 2,3-DHBA. This cross- feed assay was more efficient with strain BAM41 than with 2308, suggesting overproduction of 2,3-DHBA by the mutant. The fast-migrating catechol from BAM41 and 2308 supernatants was purified from the TLC plate, eluted and blotted on a filter. This purified substance restored the growth of AN193, confirming its identifica- tion as 2,3-DHBA. To further characterize the Brucella siderophore-deficient mutant, we tried to restore its growth in EDDA- chelated MMB medium with different substances spot- ted on filters placed on the agar surface. 2,3-DHBA (3 μ l, 10 mM) was unable to restore the growth of mutant BAM41. Ethyl acetate extracts from B . abortus 2308 culture supernatants, but not from BAM41, did complement the growth defect in the mutant. The two catechols in the 2308 supernatant were separately purified from a TLC plate and used in the complementation assay. Only the slow-migrating catechol was able to restore the growth of the mutant (Table 2). The role of siderophore in the ability of B . abortus to survive in macrophages was tested by using the B . abortus BAM41 mutant in an in vitro macrophage survival assay. The results of the experiment are shown in Fig. 4. Both B . abortus 2308 and BAM41 survived and replicated in the macrophage without significant differ- ences. Total DNA from BAM41 was digested with Eco RI and hybridized with an internal Tn 5 probe as described in Methods. A single hybridization Eco RI band of 8 kb was observed. This band was excised from an agarose gel and cloned in the plasmid vector pUC18, resulting in pSUBA41. A physical map of this DNA fragment is shown in Fig. 5. The nucleotide sequence of both ends of this DNA fragment was determined by sequencing the recombinant plasmid pSUBA41 with universal primers. To analyse the transposon insertion point we used the arbitrary PCR method described by O’Toole & Kolter (1998). Using this method we obtained and sequenced a PCR amplification product corresponding to the right flank of the transposon (Fig. 5). To determine the sequence of the left flank we used a synthetic primer derived from the previously determined sequence. These sequences were assembled in a contig of 1 kb corresponding to the B . abortus chromosome (GenBank accession no. AF361942). This sequence was compared with the non-redundant GenBank nucleotide sequence database using the program. The sequence showed strong homology with the gene vibH from Vibrio cholerae , which encodes an amidase involved in the condensation steps of vibriobactin synthesis (Keating et al ., 2000a, b). The sequence also showed homology with the amino-terminal part of E . coli entF , a gene encoding a subunit of the enterobactin biosynthesis multienzyme complex (Rusnak et al ., 1991). According to these results we may conclude that the Tn 5 insertion in BAM41 occurred at position 275, near the 5 h end of a B . abortus gene homologous to E . coli entF . This insertion resulted in the inactivation of the gene, which could be involved in the biosynthesis of the new catecholic siderophore described above. The sequence of the right end of plasmid pSUBA41 was also compared with sequences in the GenBank database. The sequence showed strong homology with the E . coli entC and entE genes, involved in the first stage of enterobactin biosynthesis. These data fit well in the physical map reported for the region encoding the 2,3- DHBA biosynthesis genes of B . abortus (Bellaire et al ., 1999). 2,3-DHBA has been reported to be the only catecholic siderophore present in the supernatant of Brucella cultures growing under iron-limiting conditions. 2,3- DHBA was able to supply iron to the bacterium and accordingly was considered as a true siderophore for Brucella (Lopez-Gon 4 i et al ., 1992). The appearance of large amounts of 2,3-DHBA or salicylic acid in culture supernatants is a phenomenon commonly observed for bacteria producing phenolate siderophores in response to iron deprivation. However, those compounds are considered to be low-affinity siderophores (Actis et al ., 1986), unable to compete with stronger iron-chelating compounds. Moreover, recent theoretical studies do not consider 2,3-DHBA to be capable of acting as a bacterial siderophore (Chipperfield & Ratledge, 2000). These facts question the role of 2,3-DHBA as a siderophore in B . abortus and suggest that Brucella either produces a stronger siderophore, different from 2,3-DHBA, or it uses a different iron assimilation system. We have observed that B . abortus 2308 was able to decolorize CAS plates, indicating that this strain secretes a siderophore. To discover the role of this siderophore in intracellular survival we have isolated a Tn 5 mutant of B . abortus 2308, named BAM41, which was negative in the CAS assay and thus considered to be siderophore- deficient. The minimal inhibitory concentration of EDDA for this mutant was lower than that of the parental strain, 2308. The correlation between absence of siderophore activity in the CAS assay and inability to grow in an iron-deprived medium indicated that the transposon insertion in this mutant was probably affecting genes involved in siderophore biosynthesis. The growth of BAM41 in a low-iron medium was stimulated by filtered supernatants from a 2308 culture grown in an iron-deprived medium, and also by ethyl acetate extracts from the same culture, indicating that an iron-related growth factor was present in both samples. Analysis of ethyl acetate extracts of B . abortus 2308 low-iron culture supernatants by TLC showed the presence of two different catechol species, one with an R identical to that of 2,3-DHBA and the other with a f lower R . The concentration of the low R catechol in f f culture supernatants was always considerably lower than that of 2,3-DHBA. When isolated from TLC plates, only the compound with the low R , but not 2,3-DHBA, f was able to complement the growth of the mutant in an iron-deprived medium and to decolorize CAS plates. These results indicated that B . abortus 2308 produced a second catecholic substance with a higher affinity for iron than the formerly reported 2,3-DHBA. Since this new compound, capable of ...
Citations
... Furthermore, the ricA gene product was found, whose interaction with the host Rab2 protein affects the BCV maturation, thus decreasing intracellular replication rates and contributing to the evasion of the innate immune response (de Barsy et al., 2011). Interestingly, 6 genes, all located in the B. ceti core genome are related to the production of brucebactin, a highlyconserved siderophore firstly identified in B. abortus and putatively acting as an iron transporter in iron-limiting conditions at the beginning of the stationary growth phase (González Carreró et al., 2002). Four additional gene products, all but one encoded by genes in the B. ceti core genome, namely the ugpB, bhuA, flhP, and fliQ, are virulence factor candidates according to the VFDB classification. ...
The Gram‐negative bacteria Brucella ceti and Brucella pinnipedialis circulate in marine environments primarily infecting marine mammals, where they cause an often‐fatal disease named brucellosis. The increase of brucellosis among several species of cetaceans and pinnipeds, together with the report of sporadic human infections, raises concerns about the zoonotic potential of these pathogens on a large scale and may pose a threat to coastal communities worldwide. Therefore, the characterization of the B. ceti and B. pinnipedialis genetic features is a priority to better understand the pathological factors that may impact global health. Moreover, an in‐depth functional analysis of the B. ceti and B. pinnipedialis genome in the context of virulence and pathogenesis was not undertaken so far. Within this picture, here we present the comparative whole‐genome characterization of all B. ceti and B. pinnipedialis genomes available in public resources, uncovering a collection of genetic tools possessed by these aquatic bacterial species compared to their zoonotic terrestrial relatives. We show that B. ceti and B. pinnipedialis genomes display a wide host‐range infection capability and a polyphyletic phylogeny within the genus, showing a genomic structure that fits the canonical definition of closeness. Functional genome annotation led to identifying genes related to several pathways involved in mechanisms of infection, others conferring pan‐susceptibility to antimicrobials and a set of virulence genes that highlight the similarity of B. ceti and B. pinnipedialis genotypes to those of Brucella spp. displaying human‐infecting phenotypes.
... The species of Bacillus, Serratia, Azotobacter, 501 Pseudomonas, Enterobacter, Azospirillum, and Rhizobium are only a few beneficial 502 plant-associated bacterial genera that secrete different forms of siderophores 503 (Ahemad and Kibret 2014). Brucella abortus strain 2308 is known to synthesize 504 brucebactin (2,3-dihydroxybenzoate), a highly efficient catechol siderophore, 505 according to Carrero et al. (2002), who used it as a siderophore for bacterial growth 506 under iron-limited conditions. Pseudomonas putida DFC31 produced pyoverdine-507 type siderophores, and their analysis revealed the existence of hydroxymate and 508 catecholate iron-chelating groups, according to Fu et al. (2007). ...
Plant growth-promoting rhizobacteria (PGPR) are closely allied with roots and can improve plant growth and inhibit the invading pathogens. The PGPR stimulates plant growth by various means, viz., increased nutrient uptake and production of hormones (IAA, gibberellins, cytokinins, etc.) and bioactive substances (to antagonize phytopathogenic microbes) along with the synthesis of enzymes that regulates plant ethylene levels. Recently, PGPR has attracted many researchers’ attention to the development of biofertilizers as an eco-friendly approach. However, potential PGPR selection is an important factor, as plants’ responses to environmental conditions often vary based on plant genotype, experimental sites, and seasons. A PGPR isolated from the native crop plants or their ecological zone is considered productive and efficient with steady results if reused at the same site and crop. Extensive studies have suggested that PGPR could have emerged as a promising and substitute chemical fertilizer method for agriculture sustainability. With this background, the interactions involving PGPR populations with plants are the current challenge to explore their use under various agroclimatic conditions. The diverse group of PGPR isolated from various plants’ rhizosphere and their role in increasing soil fertility, stress management, bioremediation, etc. are reviewed and discussed in this chapter.KeywordsBiocontrolBiofertilizersPlant hormonesRhizosphereStress management
... We anticipate that many more potentially new polyamine catechol siderophores have yet to be characterized for the remaining organisms, as they encode amide synthases as well as the remaining biosynthetic machinery for the assembly of catecholate siderophores. In the particular case of Brucella spp., brucebactin [70], its catechol siderophore, is unstable; this instability has prevented the elucidation of its structure. ...
Background
Iron is essential for bacterial survival. Bacterial siderophores are small molecules with unmatched capacity to scavenge iron from proteins and the extracellular milieu, where it mostly occurs as insoluble Fe ³⁺ . Siderophores chelate Fe ³⁺ for uptake into the cell, where it is reduced to soluble Fe ²⁺ . Siderophores are key molecules in low soluble iron conditions. The ability of bacteria to synthesize proprietary siderophores may have increased bacterial evolutionary fitness; one way that bacteria diversify siderophore structure is by incorporating different polyamine backbones while maintaining the catechol moieties.
Results
We report that Serratia plymuthica V4 produces a variety of siderophores, which we term the siderome , and which are assembled by the concerted action of enzymes encoded in two independent gene clusters. Besides assembling serratiochelin A and B with diaminopropane, S. plymuthica utilizes putrescine and the same set of enzymes to assemble photobactin, a siderophore found in the bacterium Photorhabdus luminescens . The enzymes encoded by one of the gene clusters can independently assemble enterobactin. A third, independent operon is responsible for biosynthesis of the hydroxamate siderophore aerobactin, initially described in Enterobacter aerogenes . Mutant strains not synthesizing polyamine-siderophores significantly increased enterobactin production levels, though lack of enterobactin did not impact the production of serratiochelins. Knocking out SchF0, an enzyme involved in the assembly of enterobactin alone, significantly reduced bacterial fitness.
Conclusions
This study shows the natural occurrence of serratiochelins, photobactin, enterobactin, and aerobactin in a single bacterial species and illuminates the interplay between siderophore biosynthetic pathways and polyamine production, indicating routes of molecular diversification. Given its natural yields of diaminopropane (97.75 μmol/g DW) and putrescine (30.83 μmol/g DW), S. plymuthica can be exploited for the industrial production of these compounds.
... Interestingly, the need for brucebactin appears to be host dependent. This siderophore is not required for the virulence of B. abortus 2308 in mice (409,414,415) but is essential for the virulence of this strain in pregnant goats (416) and cattle (369). The basis for this differential requirement for brucebactin in these hosts is unknown, but experimental evidence suggests that it may be linked to erythritol catabolism (370). ...
Bacteria in the genus Brucella are important human and veterinary pathogens. The abortion and infertility they cause in food animals produce economic hardships in areas where the disease has not been controlled, and human brucellosis is one of the world’s most common zoonoses. Brucella strains have also been isolated from wildlife, but we know much less about the pathobiology and epidemiology of these infections than we do about brucellosis in domestic animals. The brucellae maintain predominantly an intracellular lifestyle in their mammalian hosts, and their ability to subvert the host immune response and survive and replicate in macrophages and placental trophoblasts underlies their success as pathogens. We are just beginning to understand how these bacteria evolved from a progenitor alphaproteobacterium with an environmental niche and diverged to become highly host-adapted and host-specific pathogens. Two important virulence determinants played critical roles in this evolution: (i) a type IV secretion system that secretes effector molecules into the host cell cytoplasm that direct the intracellular trafficking of the brucellae and modulate host immune responses and (ii) a lipopolysaccharide moiety which poorly stimulates host inflammatory responses. This review highlights what we presently know about how these and other virulence determinants contribute to Brucella pathogenesis. Gaining a better understanding of how the brucellae produce disease will provide us with information that can be used to design better strategies for preventing brucellosis in animals and for preventing and treating this disease in humans.
... Consistent with previous observations (González Carreró, Sangari, Agüero, & García Lobo, 2002;Jain et al., 2011), the ΔentF strain was shown to be drastically inhibited when grown on ILM compared to control; however, its growth was interestingly found to be not influenced by the presence of rLcn2. Moreover, the complementation with full length of entF open reading frame (entF complemented) significantly recovered its replicative ability on ILM and the sensitivity with rLcn2 as well ( Figure 2f). ...
... On the other hand, because deletion of entF gene does not affect the growth of intracellular Brucella (González Carreró et al., 2002;Jain et al., 2011), the above data led to an argument that ΔentF strain might be neutral with Lcn2 signalling while residing in macrophages. To address this question, we treated cells with Lcn2 siRNA and infected with either ΔentF or entF complemented strains. ...
... Another case that may occur is that Brucella may release the unknown alternative siderophore(s) other than brucebactin or 2,3-DHBA as previously hypothesised (González Carreró et al., 2002;Jain et al., 2011), and this siderophore(s) is also bound by Lcn2 protein. However, we could not explain which case has occurred in this current study. ...
Lipocalin 2 (Lcn2) is an important innate immunity component against bacterial pathogens. In this study, we report that Lcn2 is induced by Brucella (B.) abortus infection and significantly contributes to the restriction of intracellular survival of Brucella in macrophages. We found that Lcn2 prevented iron uptake by B. abortus through two distinct mechanisms. First, Lcn2 is secreted to capture bacterial siderophore(s) and abrogate iron import by Brucella. Second, Lcn2 decreases the intracellular iron levels during Brucella infection, which probably deprives the invading Brucella of the iron source needed for growth. Suppression of Lcn2 signaling resulted in a marked induction of anti-inflammatory cytokine, interleukin 10 (IL-10) which was shown to play a major role in Lcn2-induced antibrucella immunity. Similarly, IL-6 was also found to be increased when Lcn2 signaling is abrogated; however, this induction was thought to be an alternative pathway that rescues the cell from infection when the effective Lnc2 pathway is repressed. Furthermore, Lcn2 deficiency also caused a marked decrease in brucellacidal effectors, such as reactive oxygen species (ROS) and nitric oxide (NO), but not the phagolysosome fusion. Taken together, our results indicate that Lcn2 is required for the efficient restriction of intracellular B. abortus growth that is through limiting iron acquisition and shifting cells to pro-inflammatory brucellacidal activity in murine macrophages.
... The same could be true if the bacterium has to face deprivation of iron [37][38][39] or other essential compounds, or if the host cell metabolism is modified, as a result of the recognition of the bacterium by the innate immune system. Future studies directed toward investigation of cellcycle progression in different types of host cell, such as trophoblasts or macrophages (activated or not), will provide a deeper understanding of the interface between host cell biology, Brucella cell cycle, and infection. ...
Brucellae are facultative intracellular pathogens. The recent development of methods and genetically engineered strains allowed the description of cell-cycle progression of Brucella abortus, including unipolar growth and the ordered initiation of chromosomal replication. B. abortus cell-cycle progression is coordinated with intracellular trafficking in the endosomal compartments. Bacteria are first blocked at the G1 stage, growth and chromosome replication being resumed shortly before reaching the intracellular proliferation compartment. The control mechanisms of cell cycle are similar to those reported for the bacterium Caulobacter crescentus, and they are crucial for survival in the host cell. The development of single-cell analyses could also be applied to other bacterial pathogens to investigate their cell-cycle progression during infection.
... Brucellae produce the monocatechol siderophore 2,3-dihydroxybenzoic acid (2,3-DHBA) in response to iron limitation, and the genes that encode this siderophore (49) are in an operon (BRA0013 to BRA0016) found in region 5. Production of this siderophore appears to be an adaptation to the environment found in the ruminant placenta (50)(51)(52). Another gene involved in iron regulation is dhbR. ...
Brucella species include important zoonotic pathogens that have a substantial impact on both agriculture and human health throughout
the world. Brucellae are thought of as “stealth pathogens” that escape recognition by the host innate immune response, modulate
the acquired immune response, and evade intracellular destruction. We analyzed the genome sequences of members of the family
Brucellaceae to assess its evolutionary history from likely free-living soil-based progenitors into highly successful intracellular pathogens.
Phylogenetic analysis split the genus into two groups: recently identified and early-dividing “atypical” strains and a highly
conserved “classical” core clade containing the major pathogenic species. Lateral gene transfer events brought unique genomic
regions into Brucella that differentiated them from Ochrobactrum and allowed the stepwise acquisition of virulence factors that include a type IV secretion system, a perosamine-based O antigen,
and systems for sequestering metal ions that are absent in progenitors. Subsequent radiation within the core Brucella resulted in lineages that appear to have evolved within their preferred mammalian hosts, restricting their virulence to become
stealth pathogens capable of causing long-term chronic infections.
... Further evidence for the possible involvement of erythritol metabolism in virulence has been suggested by Burkhardt et al., who demonstrated that inactivation of the eryC gene significantly reduced the intramacrophagic and intramurine fitness of B. suis [11]. Moreover, erythritol metabolism is connected in Brucella with iron uptake by the production of siderophores 2,3-dihydroxy- benzoate (2,3-DHBA) and brucebactin [12],[13]. An entC mutant unable to synthesise DHBA was not able to cause abortions in pregnant goats, underscoring the role played by DHBA in the virulence [14]. ...
Bacteria of the genus Brucella have the unusual capability to catabolize erythritol and this property has been associated with their virulence mainly because of the presence of erythritol in bovine foetal tissues and because the attenuated S19 vaccine strain is the only Brucella strain unable to oxydize erythritol. In this work we have analyzed the transcriptional changes produced in Brucella by erythritol by means of two high throughput approaches: RNA hybridization against a microarray containing most of Brucella ORF's constructed from the Brucella ORFeome and next generation sequencing of Brucella mRNA in an Illumina GAIIx platform. The results obtained showed the overexpression of a group of genes, many of them in a single cluster around the ery operon, able to co-ordinately mediate the transport and degradation of erythritol into three carbon atoms intermediates that will be then converted into fructose-6P (F6P) by gluconeogenesis. Other induced genes participating in the nonoxidative branch of the pentose phosphate shunt and the TCA may collaborate with the ery genes to conform an efficient degradation of sugars by this route. On the other hand, several routes of amino acid and nucleotide biosynthesis are up-regulated whilst amino acid transport and catabolism genes are down-regulated. These results corroborate previous descriptions indicating that in the presence of erythritol, this sugar was used preferentially over other compounds and provides a neat explanation of the the reported stimulation of growth induced by erythritol.
... The approach described in the previous paragraph was also used to introduce a bhuQ mutation into B. abortus BHB2 (6). BHB2 has an unmarked, in-frame deletion in its dhbC gene, which renders it unable to produce the two siderophores produced by Brucella strains, 2,3-dihydroxybenzoic acid (15) and brucebactin (12). The B. abortus dhbC bhuQ double mutant constructed in this fashion was given the designation JFO1. ...
The Brucella BhuQ protein is a homolog of the Bradyrhizobium japonicum heme oxygenases HmuD and HmuQ. To determine if this protein plays a role in the ability of Brucella abortus 2308 to use heme as an iron source, an isogenic bhuQ mutant was constructed and its phenotype evaluated. Although the Brucella abortus bhuQ mutant DCO1 did not exhibit a defect in its capacity to use heme as an iron source or evidence of increased heme toxicity
in vitro, this mutant produced increased levels of siderophore in response to iron deprivation compared to 2308. Introduction of a
bhuQ mutation into the B. abortus dhbC mutant BHB2 (which cannot produce siderophores) resulted in a severe growth defect in the dhbC bhuQ double mutant JFO1 during cultivation under iron-restricted conditions, which could be rescued by the addition of FeCl3, but not heme, to the growth medium. The bhuQ gene is cotranscribed with the gene encoding the iron-responsive regulator RirA, and both of these genes are repressed by
the other major iron-responsive regulator in the alphaproteobacteria, Irr. The results of these studies suggest that B. abortus 2308 has at least one other heme oxygenase that works in concert with BhuQ to allow this strain to efficiently use heme as
an iron source. The genetic organization of the rirA-bhuQ operon also provides the basis for the proposition that BhuQ may perform a previously unrecognized function by allowing the
transcriptional regulator RirA to recognize heme as an iron source.
... Siderophores are low molecular weight chelators that microbes release into their external environment to capture iron (Raymond and Dertz, 2004). Brucella strains produce two catechol siderophores when exposed to iron deprivation -2,3-dihydroxybenzoic acid (2,3-DHBA) and the 2,3-DHBA-based molecule brucebactin (López-Goñi et al., 1992;González-Carreró et al., 2002). Owing to its instability in the laboratory, the precise structure of brucebactin is currently unknown. ...
... A B. abortus dhbC mutant, which produces neither 2,3-DHBA nor brucebactin, for instance, does not cause abortion in pregnant goats (Bellaire et al., 2000) or cattle (Bellaire et al., 2003a) (Fig. 3). In contrast, this mutant and isogenic B. abortus mutants that produce 2,3-DHBA but cannot convert it to brucebactin display wildtype virulence in the mouse model of chronic infection (Bellaire et al., 1999;González-Carreró et al., 2002;Parent et al., 2002). ...
... A final point that bears consideration is that the vast majority of the studies that have evaluated the contributions of Brucella metal acquisition to virulence have been performed in the mouse model of chronic infection, which is used as a measure of the ability of these strains to survive and replicate in host macrophages. But as the studies with B. abortus siderophore biosynthesis mutants well demonstrate (Bellaire et al., 1999(Bellaire et al., , 2000(Bellaire et al., , 2003aGonzález-Carreró et al., 2002;Parent et al., 2002), the results obtained with the mouse model may not always predict how a mutant will behave in the natural host, especially in pregnant ruminants. The sources of iron (e.g. ...
Similar to other bacteria, Brucella strains require several biologically essential metals for their survival in vitro and in vivo. Acquiring sufficient levels of some of these metals, particularly iron, manganese and zinc, is especially challenging in the mammalian host, where sequestration of these micronutrients is a well-documented component of both the innate and acquired immune responses. This review describes the Brucella metal transporters that have been shown to play critical roles in the virulence of these bacteria in experimental and natural hosts.
