<i>Erwinia chrysanthemi</i>Iron Metabolism: the Unexpected Implication of the Inner Membrane Platform within the Type II Secretion System

Douet, Vanessa; Expert, Dominique; Barras, Frédéric; Py, Béatrice

doi:10.1128/jb.00845-08

Cited by 9 publications

(9 citation statements)

References 62 publications

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“…Our transcriptome profiling and phenotypic analysis demonstrate that inactivation of the T2S system has severe consequences on iron homeostasis and the overall oxidative status of V. cholerae cells. In contrast to previous suggestions for other gram-negative bacteria (17,22), we show that the T2S system is not directly engaged in iron acquisition in V. cholerae.…”

Section: Vol 191 2009 T2s System Iron Homeostasis and Stress Respcontrasting

confidence: 54%

“…Moreover, it was reported that certain T2S mutants of E. chrysanthemi lack a periplasmic FbpA-like iron binding protein and display increased susceptibility to oxidants and streptonigrin in the stationary phase of growth (17). Our comparative analysis of different T2S and NtolA mutants exhibiting similarly altered outer membrane integrity, however, suggests that changes in iron homeostasis as well as in oxidative stress are not unique to T2S mutants but rather occur in response to cell envelope perturbation.…”

Section: Vol 191 2009 T2s System Iron Homeostasis and Stress Respmentioning

confidence: 56%

“…Based on these results, it has been suggested that the T2S system might be involved in iron acquisition. Similarly, certain T2S mutants of Erwinia chrysanthemi exhibit defects indicative of changes in iron homeostasis (17). It has also been noted that the level of aconitate hydratase, an iron-sulfur cluster-containing enzyme, is reduced in L. pneumophila T2S mutants (16).…”

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confidence: 97%

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Cell Envelope Perturbation Induces Oxidative Stress and Changes in Iron Homeostasis inVibrio cholerae

et al. 2009

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The Vibrio cholerae type II secretion (T2S) machinery is a multiprotein complex that spans the cell envelope. When the T2S system is inactivated, cholera toxin and other exoproteins accumulate in the periplasmic compartment. Additionally, loss of secretion via the T2S system leads to a reduced growth rate, compromised outer membrane integrity, and induction of the extracytoplasmic stress factor RpoE (A. E. Sikora, S. R. Lybarger, and M. Sandkvist, J. Bacteriol. 189:8484-8495, 2007). In this study, gene expression profiling reveals that inactivation of the T2S system alters the expression of genes encoding cell envelope components and proteins involved in central metabolism, chemotaxis, motility, oxidative stress, and iron storage and acquisition. Consistent with the gene expression data, molecular and biochemical analyses indicate that the T2S mutants suffer from internal oxidative stress and increased levels of intracellular ferrous iron. By using a tolA mutant of V. cholerae that shares a similar compromised membrane phenotype but maintains a functional T2S machinery, we show that the formation of radical oxygen species, induction of oxidative stress, and changes in iron physiology are likely general responses to cell envelope damage and are not unique to T2S mutants. Finally, we demonstrate that disruption of the V. cholerae cell envelope by chemical treatment with polymyxin B similarly results in induction of the RpoE-mediated stress response, increased sensitivity to oxidants, and a change in iron metabolism. We propose that many types of extracytoplasmic stresses, caused either by genetic alterations of outer membrane constituents or by chemical or physical damage to the cell envelope, induce common signaling pathways that ultimately lead to internal oxidative stress and misregulation of iron homeostasis.Vibrio cholerae, a rod-shaped, highly motile, gram-negative bacterium, is the causative agent of the life threatening diarrheal disease cholera (59). The type II secretion (T2S) system plays an important role in the pathogenesis of V. cholerae by secreting cholera toxin (63), which is largely responsible for the symptoms of the disease (33). The T2S system is widespread and well conserved in gram-negative bacteria inhabiting a variety of ecological niches and likely contributes to environmental survival as well as to virulence (11,21). In V. cholerae, secretion via the T2S machinery is supported by a transenvelope complex of 12 Eps proteins (EpsC to EpsN) and the type 4 prepilin peptidase PilD (VcpD) (25,44,63). Transport of exoproteins by the T2S system occurs via a two-step process. The first step, which is either Sec or Tat dependent, requires recognition of the N-terminal signal peptide of the exoproteins and translocation through the inner membrane to the periplasm. Then the folded proteins engage the T2S machinery and are subsequently exported across the outer membrane to the extracellular milieu (23,29).Besides periplasmic accumulation of exoproteins, additional phenotypes of T2S mutants are reporte...

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Section: Vol 191 2009 T2s System Iron Homeostasis and Stress Respcontrasting

confidence: 54%

Section: Vol 191 2009 T2s System Iron Homeostasis and Stress Respmentioning

confidence: 56%

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confidence: 97%

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Cell Envelope Perturbation Induces Oxidative Stress and Changes in Iron Homeostasis inVibrio cholerae

et al. 2009

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“…The modified ferrozine assay demonstrated; however, that the free iron pool was markedly diminished. This observation is in accordance with our previously reported finding that ∆ fupA is highly resistant to streptonigrin [ 9 ], which is considered to be a measure of a small free intracellular iron pool [ 20 , 21 ]. Based on this previous and the present observations, it appears that the poor growth of ∆ fupA probably is not related to heme utilization per se but rather to the role of FupA to maintain an iron pool that is easily accessible to effectively support growth.…”

Section: Discussionsupporting

confidence: 93%

Mechanisms of Heme Utilization by Francisella tularensis

et al. 2015

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Francisella tularensis is a highly virulent facultative intracellular pathogen causing the severe disease tularemia in mammals. As for other bacteria, iron is essential for its growth but very few mechanisms for iron acquisition have been identified. Here, we analyzed if and how F. tularensis can utilize heme, a major source of iron in vivo. This is by no means obvious since the bacterium lacks components of traditional heme-uptake systems. We show that SCHU S4, the prototypic strain of subspecies tularensis, grew in vitro with heme as the sole iron source. By screening a SCHU S4 transposon insertion library, 16 genes were identified as important to efficiently utilize heme, two of which were required to avoid heme toxicity. None of the identified genes appeared to encode components of a potential heme-uptake apparatus. Analysis of SCHU S4 deletion mutants revealed that each of the components FeoB, the siderophore system, and FupA, contributed to the heme-dependent growth. In the case of the former two systems, iron acquisition was impaired, whereas the absence of FupA did not affect iron uptake but led to abnormally high binding of iron to macromolecules. Overall, the present study demonstrates that heme supports growth of F. tularensis and that the requirements for the utilization are highly complex and to some extent novel.

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“…We have chosen the phytopathogenic bacterium D. dadantii as our model organism because the structural organization and function of the Out system, as well as its secreted cargo proteins, have been extensively studied. 3,11,14 Moreover, D. dadantii is a causative agent of soft-rot disease in all major groups of dicotyledons and has served as a model in studies elucidating bacterial virulence factors in plant pathogenicity. 5 We reasoned that the delivery of the T2S-exoproteins could be blocked by an inhibitory molecule in multiple ways, including (1) plugging the secretion pore, (2) affecting steps in the assembly of the secretion machinery, (3) disturbing the recognition of the cargo protein by the T2S complex, (4) disrupting interactions between the individual constituents of the T2S complex, (5) interfering with either the Sec or the Tat transport systems located within the cytoplasmic membrane, or (6) inhibiting synthesis of the T2S system (Fig.…”

Section: Design Of the Assay For Screening Of The T2s Inhibitorsmentioning

confidence: 99%

Development of a Quantitative Assay Amenable for High-Throughput Screening to Target the Type II Secretion System for New Treatments against Plant-Pathogenic Bacteria

et al. 2013

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Plant-pathogenic bacteria are the causative agents of diseases in important agricultural crops and ornamental plants. The severe economic burden of these diseases requires seeking new approaches for their control, particularly because phytopathogenic bacteria are often resistant to available treatments. The type II secretion (T2S) system is a key virulence factor used by major groups of phytopathogenic bacteria. The T2S machinery transports many hydrolytic enzymes responsible for degradation of the plant cell wall, thus enabling successful colonization and dissemination of the bacteria in the plant host. The genetic inactivation of the T2S system leads to loss of virulence, which strongly suggests that targeting the T2S could enable new treatments against plant-pathogenic bacteria. Accordingly, we have designed and optimized an assay to identify small-molecule inhibitors of the T2S system. This assay uses a double parametric output: measurement of bacterial growth and the enzymatic activity of cellulase, which is secreted via the T2S pathway in our model organism Dickeya dadantii. The assay was evaluated by screening natural extracts, culture filtrates isolated from rhizosphere bacteria, and a collection of pharmaceutically active compounds in LOPAC(1280). The calculated Z' values of 0.63, 0.63, and 0.58, respectively, strongly suggest that the assay is applicable for a high-throughput screening platform.

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Erwinia chrysanthemiIron Metabolism: the Unexpected Implication of the Inner Membrane Platform within the Type II Secretion System

Cited by 9 publications

References 62 publications

Cell Envelope Perturbation Induces Oxidative Stress and Changes in Iron Homeostasis inVibrio cholerae

Cell Envelope Perturbation Induces Oxidative Stress and Changes in Iron Homeostasis inVibrio cholerae

Mechanisms of Heme Utilization by Francisella tularensis

Development of a Quantitative Assay Amenable for High-Throughput Screening to Target the Type II Secretion System for New Treatments against Plant-Pathogenic Bacteria

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