Contact-Dependent Growth Inhibition Causes Reversible Metabolic Downregulation in
            <i>Escherichia coli</i>

Aoki, Stephanie K.; Webb, Jeremy S.; Braaten, Bruce A.; Low, David A.

doi:10.1128/jb.01437-08

Cited by 93 publications

(115 citation statements)

References 54 publications

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“…In the case of EC93, two secreted proteins encoded by cdiA and cdiB (expressed in early logarithmic phase) bind to BamA in the outer membrane of target cells (E. coli K-12) to inhibit their growth. A protein encoded by a third gene, cdiI, protects the inhibitor strain from self-inhibition (2). PCR analysis of our inhibitor strains showed that they do not possess the cdiI immunity gene.…”

Section: Discussionmentioning

confidence: 99%

Proximity-Dependent Inhibition in Escherichia coli Isolates from Cattle

Sawant

Casavant

Call

et al. 2011

Appl Environ Microbiol

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We describe a novel proximity-dependent inhibition phenotype of Escherichia coli that is expressed when strains are cocultured in defined minimal media. When cocultures of "inhibitor" and "target" strains approached a transition between logarithmic and stationary growth, target strain populations rapidly declined >4 log CFU per ml over a 2-h period. Inhibited strains were not affected by exposure to conditioned media from inhibitor and target strain cocultures or when the inhibitor and target strains were incubated in shared media but physically separated by a 0.4-m-pore-size membrane. There was no evidence of lytic phage or extracellular bacteriocin involvement, unless the latter was only present at effective concentrations within immediate proximity of the inhibited cells. The inhibitory activity observed in this study was effective against a diversity of E. coli strains, including enterohemorrhagic E. coli serotype O157:H7, enterotoxigenic E. coli expressing F5 (K99) and F4 (K88) fimbriae, multidrug-resistant E. coli, and commensal E. coli. The decline in counts of target strains in coculture averaged 4.8 log CFU/ml (95% confidence interval, 4.0 to 5.5) compared to their monoculture counts. Coculture of two inhibitor strains showed mutual immunity to inhibition. These results suggest that proximity-dependent inhibition can be used by bacteria to gain a numerical advantage when populations are entering stationary phase, thus setting the stage for a competitive advantage when growth conditions improve.With the discovery of quorum sensing in the 1960s and 1970s, in comparison to the discovery of colicins in the 1920s, it became evident that populations of individual cells are capable of coordinating functions by using signaling molecules for communication. These communications can enhance fitness in a multispecies community, help exploit nutrients more efficiently, increase cooperation with neighboring cells, or harm competing bacteria. Some of the cell-to-cell communications have been well characterized. Streptococcus oralis 34 secretes an autoinducer that signals Actinomyces naeslundii T14V to congregate with S. oralis 34 and form a mutualistic biofilm in saliva (21). Vibrio cholerae uses autoinducers to shut down expression of virulence factors and biofilm formation at high cell densities (13). As an SOS response, certain bacteria can produce toxins, called bacteriocins, which can kill a narrow spectrum of competing cells that express suitable cell surface receptors (8)(9)(10)14). Bacteria can also produce inhibitory phage particles and iron-sequestering aerobactin to gain an advantage over competing bacteria (6,23).Many of these mechanisms enhance the fitness of bacterial strains in a given environment. Khachatryan et al. in 2004 observed a fitness trait allowing certain multidrug-resistant Escherichia coli in Holstein calves to dominate the enteric E. coli population (16). Neither antimicrobial drug use nor the presence of antimicrobial resistance genes was associated with the fitness trait observed in the ...

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Section: Discussionmentioning

confidence: 99%

Proximity-Dependent Inhibition in Escherichia coli Isolates from Cattle

Sawant

Casavant

Call

et al. 2011

Appl Environ Microbiol

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“…Our results together with previous predictions (25) also suggest that many other CdiA-CT toxin domains may have similar structures despite sharing very little sequence identity. However, we note that some CDI toxin family members must possess other folds because the E. coli EC93 toxin forms pores in target cell membranes (6), and CdiA-CTs from B. pseudomallei K96243 and Erwinia chrysanthemi EC16 share significant sequence identity with colicins E5 and E3, respectively (5,26).…”

Section: Discussionmentioning

confidence: 99%

Structural basis of toxicity and immunity in contact-dependent growth inhibition (CDI) systems

Morse¹,

Nikolakakis²,

Willett

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

168

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Contact-dependent growth inhibition (CDI) systems encode polymorphic toxin/immunity proteins that mediate competition between neighboring bacterial cells. We present crystal structures of CDI toxin/ immunity complexes from Escherichia coli EC869 and Burkholderia pseudomallei 1026b. Despite sharing little sequence identity, the toxin domains are structurally similar and have homology to endonucleases. The EC869 toxin is a Zn 2+ -dependent DNase capable of completely degrading the genomes of target cells, whereas the Bp1026b toxin cleaves the aminoacyl acceptor stems of tRNA molecules. Each immunity protein binds and inactivates its cognate toxin in a unique manner. The EC869 toxin/immunity complex is stabilized through an unusual β-augmentation interaction. In contrast, the Bp1026b immunity protein exploits shape and charge complementarity to occlude the toxin active site. These structures represent the initial glimpse into the CDI toxin/immunity network, illustrating how sequence-diverse toxins adopt convergent folds yet retain distinct binding interactions with cognate immunity proteins. Moreover, we present visual demonstration of CDI toxin delivery into a target cell.structural biology | bacterial competition | β-complementation | tRNase activity

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“…The CdiA-CT EC93 domain deployed by Escherichia coli isolate EC93 increases target-cell permeability to protons (9,10), suggesting that this toxin forms pores in the inner membrane. Many other CdiA-CT toxins are nucleases that must be delivered into the target-cell cytoplasm to inhibit growth.…”

mentioning

confidence: 99%

Activation of contact-dependent antibacterial tRNase toxins by translation elongation factors

Jones

Garza-Sánchez

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Contact-dependent growth inhibition (CDI) is a mechanism by which bacteria exchange toxins via direct cell-to-cell contact. CDI systems are distributed widely among Gram-negative pathogens and are thought to mediate interstrain competition. Here, we describe tsf mutations that alter the coiled-coil domain of elongation factor Ts (EF-Ts) and confer resistance to the CdiA-CT EC869 tRNase toxin from enterohemorrhagic Escherichia coli EC869. Although EF-Ts is required for toxicity in vivo, our results indicate that it is dispensable for tRNase activity in vitro. We find that CdiA-CT EC869 binds to elongation factor Tu (EF-Tu) with high affinity and this interaction is critical for nuclease activity. Moreover, in vitro tRNase activity is GTP-dependent, suggesting that CdiA-CT EC869 only cleaves tRNA in the context of translationally active GTP·EF-Tu·tRNA ternary complexes. We propose that EF-Ts promotes the formation of GTP·EF-Tu·tRNA ternary complexes, thereby accelerating substrate turnover for rapid depletion of target-cell tRNA.cell communication | protein synthesis | toxin-immunity proteins | ribonuclease | bacterial competition

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Contact-Dependent Growth Inhibition Causes Reversible Metabolic Downregulation in Escherichia coli

Cited by 93 publications

References 54 publications

Proximity-Dependent Inhibition in Escherichia coli Isolates from Cattle

Proximity-Dependent Inhibition in Escherichia coli Isolates from Cattle

Structural basis of toxicity and immunity in contact-dependent growth inhibition (CDI) systems

Activation of contact-dependent antibacterial tRNase toxins by translation elongation factors

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