Direct live imaging of cell–cell protein transfer by transient outer membrane fusion in Myxococcus xanthus

Ducret, Adrien; Fleuchot, Betty; Bergam, Ptissam; Mignot, Tâm

doi:10.7554/elife.00868

Cited by 82 publications

(91 citation statements)

References 28 publications

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“…For example, chains of vesicles in Myxococcus xanthus are important for cell-cell signaling; outer membrane exchange between cells facilitated by these structures can help manage stress at the population level (9,10). Cryo-electron microscopy (cryo-EM) images of the M. xanthus vesicle chains show characteristics similar to those we observed for S. oneidensis nanowires using atomic force microscopy and fluorescence microscopy (8,11,12). Recently, tube-like membrane connections have been identified between Desulfovibrio vulgaris and Clostridium acetobutylicum, as well as between Escherichia coli and Acinetobacter baylyi, for the purpose of exchanging cellular materials and cross-feeding between each pair of species (13,14).…”

supporting

confidence: 51%

Regulation of Gene Expression in Shewanella oneidensis MR-1 during Electron Acceptor Limitation and Bacterial Nanowire Formation

Barchinger

Pirbadian

Sambles

et al. 2016

Appl Environ Microbiol

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In limiting oxygen as an electron acceptor, the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 rapidly forms nanowires, extensions of its outer membrane containing the cytochromes MtrC and OmcA needed for extracellular electron transfer. RNA sequencing (RNA-Seq) analysis was employed to determine differential gene expression over time from triplicate chemostat cultures that were limited for oxygen. We identified 465 genes with decreased expression and 677 genes with increased expression. The coordinated increased expression of heme biosynthesis, cytochrome maturation, and transport pathways indicates that S. oneidensis MR-1 increases cytochrome production, including the transcription of genes encoding MtrA, MtrC, and OmcA, and transports these decaheme cytochromes across the cytoplasmic membrane during electron acceptor limitation and nanowire formation. In contrast, the expression of the mtrA and mtrC homologs mtrF and mtrD either remains unaffected or decreases under these conditions. The ompW gene, encoding a small outer membrane porin, has 40-fold higher expression during oxygen limitation, and it is proposed that OmpW plays a role in cation transport to maintain electrical neutrality during electron transfer. The genes encoding the anaerobic respiration regulator cyclic AMP receptor protein (CRP) and the extracytoplasmic function sigma factor RpoE are among the transcription factor genes with increased expression. RpoE might function by signaling the initial response to oxygen limitation. Our results show that RpoE activates transcription from promoters upstream of mtrC and omcA. The transcriptome and mutant analyses of S. oneidensis MR-1 nanowire production are consistent with independent regulatory mechanisms for extending the outer membrane into tubular structures and for ensuring the electron transfer function of the nanowires. IMPORTANCEShewanella oneidensis MR-1 has the capacity to transfer electrons to its external surface using extensions of the outer membrane called bacterial nanowires. These bacterial nanowires link the cell's respiratory chain to external surfaces, including oxidized metals important in bioremediation, and explain why S. oneidensis can be utilized as a component of microbial fuel cells, a form of renewable energy. In this work, we use differential gene expression analysis to focus on which genes function to produce the nanowires and promote extracellular electron transfer during oxygen limitation. Among the genes that are expressed at high levels are those encoding cytochrome proteins necessary for electron transfer. Shewanella coordinates the increased expression of regulators, metabolic pathways, and transport pathways to ensure that cytochromes efficiently transfer electrons along the nanowires.

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supporting

confidence: 51%

Regulation of Gene Expression in Shewanella oneidensis MR-1 during Electron Acceptor Limitation and Bacterial Nanowire Formation

Barchinger

Pirbadian

Sambles

et al. 2016

Appl Environ Microbiol

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“…Other studies have demonstrated a transfer of outer-membrane proteins between the two strains of Myxococcus xanthus, a wildtype strain acting as donor cell and a mutant strain acting as recipient for the product of the missing gene 41,42 . A form of bacterial communication has been described between adjacent cells via connecting 'nanotubes', even between Gram-positive and Gram-negative bacteria 23 , which could resemble the cell-cell interaction between C. acetobutylicum and D. vulgaris described here, where we show a bidirectional exchange.…”

Section: Discussionmentioning

confidence: 99%

Nutritional stress induces exchange of cell material and energetic coupling between bacterial species

et al. 2015

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Knowledge of the behaviour of bacterial communities is crucial for understanding biogeochemical cycles and developing environmental biotechnology. Here we demonstrate the formation of an artificial consortium between two anaerobic bacteria, Clostridium acetobutylicum (Gram-positive) and Desulfovibrio vulgaris Hildenborough (Gram-negative, sulfate-reducing) in which physical interactions between the two partners induce emergent properties. Molecular and cellular approaches show that tight cell-cell interactions are associated with an exchange of molecules, including proteins, which allows the growth of one partner (D. vulgaris) in spite of the shortage of nutrients. This physical interaction induces changes in expression of two genes encoding enzymes at the pyruvate crossroads, with concomitant changes in the distribution of metabolic fluxes, and allows a substantial increase in hydrogen production without requiring genetic engineering. The stress induced by the shortage of nutrients of D. vulgaris appears to trigger the interaction.

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“…To identify whether these intercellular connections consist of membrane-derived lipids, 9-h-old interspecific cocultures of the cross-feeding mutants A. baylyi DhisDDtrpR and E. coli DtrpBDhisL were labelled with the lipophilic dye DiO that intercalates in lipid membranes 20 . Subsequent in vivo fluorescent imaging of the otherwise mCherry-labelled cells should pinpoint the potential lipid-based nature of extracellular appendages by their green fluorescence.…”

Section: Construction Of Synthetic Cross-feeding Interactionsmentioning

confidence: 99%

“…Such mechanisms include, for example, the production of outer membrane vesicles, as they are used by many bacterial species to deliver cargo to other cells [12][13][14][15][16] . Alternatively, bacterial cells may connect via channels 17 , nanotubes 18 , pili 19 or transiently fuse their outer membrane 20 to transfer cytoplasmic components or outer membrane materials.…”

mentioning

confidence: 99%

“…Second, chemical signals that help to coordinate social activities within microbial communities are trafficked between cells 16 . Third, proteins can be transferred between cells 18,20 , which are involved in social movement 14 or serve predatory bacteria as interspecific killing factors 15 . Another possibility, which remains virtually unexplored, is the utilization of intercellular connections to transfer nutrients between bacterial cells.…”

mentioning

confidence: 99%

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Metabolic cross-feeding via intercellular nanotubes among bacteria

et al. 2015

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Bacteria frequently exchange metabolites by diffusion through the extracellular environment, yet it remains generally unclear whether bacteria can also use cell-cell connections to directly exchange nutrients. Here we address this question by engineering cross-feeding interactions within and between Acinetobacter baylyi and Escherichia coli, in which two distant bacterial species reciprocally exchange essential amino acids. We establish that in a well-mixed environment E. coli, but likely not A. baylyi, can connect to other bacterial cells via membranederived nanotubes and use these to exchange cytoplasmic constituents. Intercellular connections are induced by auxotrophy-causing mutations and cease to establish when amino acids are externally supplied. Electron and fluorescence microscopy reveal a network of nanotubular structures that connects bacterial cells and enables an intercellular transfer of cytoplasmic materials. Together, our results demonstrate that bacteria can use nanotubes to exchange nutrients among connected cells and thus help to distribute metabolic functions within microbial communities.

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Direct live imaging of cell–cell protein transfer by transient outer membrane fusion in Myxococcus xanthus

Cited by 82 publications

References 28 publications

Regulation of Gene Expression in Shewanella oneidensis MR-1 during Electron Acceptor Limitation and Bacterial Nanowire Formation

Regulation of Gene Expression in Shewanella oneidensis MR-1 during Electron Acceptor Limitation and Bacterial Nanowire Formation

Nutritional stress induces exchange of cell material and energetic coupling between bacterial species

Metabolic cross-feeding via intercellular nanotubes among bacteria

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