Colicin Biology

Albert Einstein College of Medicine, New York, New York, United States
Microbiology and Molecular Biology Reviews (Impact Factor: 14.61). 04/2007; 71(1):158-229. DOI: 10.1128/MMBR.00036-06
Source: PubMed


Colicins are proteins produced by and toxic for some strains of Escherichia coli. They are produced by strains of E. coli carrying a colicinogenic plasmid that bears the genetic determinants for colicin synthesis, immunity, and release. Insights gained into each fundamental aspect of their biology are presented: their synthesis, which is under SOS regulation; their release into the extracellular medium, which involves the colicin lysis protein; and their uptake mechanisms and modes of action. Colicins are organized into three domains, each one involved in a different step of the process of killing sensitive bacteria. The structures of some colicins are known at the atomic level and are discussed. Colicins exert their lethal action by first binding to specific receptors, which are outer membrane proteins used for the entry of specific nutrients. They are then translocated through the outer membrane and transit through the periplasm by either the Tol or the TonB system. The components of each system are known, and their implication in the functioning of the system is described. Colicins then reach their lethal target and act either by forming a voltage-dependent channel into the inner membrane or by using their endonuclease activity on DNA, rRNA, or tRNA. The mechanisms of inhibition by specific and cognate immunity proteins are presented. Finally, the use of colicins as laboratory or biotechnological tools and their mode of evolution are discussed.

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Available from: Roland Lloubes
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    • "Colicins are plasmid-encoded bacteriocins secreted by Escherichia coli which kill closely related competing bacteria by penetrating their outer membranes and delivering a toxic domain into or beyond the inner membrane (Cascales et al., 2007). Initially, they bind a cell surface receptor, after which they recruit a translocator protein to cross the outer membrane. "
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    ABSTRACT: Most colicins kill Escherichia coli cells by membrane pore formation or nuclease activity and, superficially, the mechanisms are similar; receptor binding, translocon recruitment, periplasmic receptor binding and membrane insertion. However, in detail they employ a wide variety of molecular interactions that reveal a high degree of evolutionary diversification. Group A colicins bind to members of the TolQRAB complex in the periplasm and heterotrimeric complexes of Colicin-TolA-TolB have been observed for both colicins A and E9. Colicin N, the smallest and simplest pore -forming colicin, binds only to TolA and we show here that it uses the binding site normally used by TolB, effectively preventing formation of the larger complex used by other colicins. Colicin N binding to TolA is by β-strand addition with a Kd of 1uM compared to 40 µM for the TolA-B interaction. The β-strand addition and Colicin N activity can be abolished by single proline point mutations in TolA, which each remove one backbone hydrogen bond. By also blocking TolA-TolB binding these point mutations confer a complete tol phenotype which destabilises the outer membrane, prevents both colicin A and E9 activity and abolishes phage protein binding to TolA. These are the only point mutations known to have such pleiotropic effects and show that the TolA-TolB β-strand addition is essential for Tol function. This formation of this simple binary colicin N-TolA complex provides yet more evidence of a distinct translocation route for Colicin N and may help to explain the unique toxicity of its N terminal domain.
    Full-text · Article · Dec 2014 · Microbiology
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    • "These include colicin A, B, E1, Ia, Ib, K, and N; (2) Nuclease type colicins: colicins containing DNase, 16S rRNase, and tRNase to non-specifically digest DNA and RNA of bacteria. These include colicin E2 to E9; (3) Peptidoglycanase type colicins: these proteins can digest the peptidoglycan precursor, leading to an inability to synthesize peptidoglycan and bacterial death (Cascales et al., 2007). "
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    ABSTRACT: Bacteriocins are a kind of ribosomal synthesized antimicrobial peptides produced by bacteria, which can kill or inhibit bacterial strains closely-related or non-related to produced bacteria, but will not harm the bacteria themselves by specific immunity proteins. Bacteriocins become one of the weapons against microorganisms due to the specific characteristics of large diversity of structure and function, natural resource, and being stable to heat. Many recent studies have purified and identified bacteriocins for application in food technology, which aims to extend food preservation time, treat pathogen disease and cancer therapy, and maintain human health. Therefore, bacteriocins may become a potential drug candidate for replacing antibiotics in order to treat multiple drugs resistance pathogens in the future. This review article summarizes different types of bacteriocins from bacteria. The latter half of this review focuses on the potential applications in food science and pharmaceutical industry.
    Full-text · Article · Dec 2014 · Frontiers in Microbiology
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    • "The temporal dynamics of range expansions was simulated employing a Gillespie algorithm [44]. The algorithm also governed the toxin interaction between sensitive and toxic lattice sites (we assumed that 3% of initially and newly colonized lattice sites dominated by the C strain were toxic [45]). Our inclusion of this interaction explicitly accounted for the long-range diffusion of colicins (a nearest-neighbour interaction would have been insufficient to recover experimental results). "
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    ABSTRACT: Dispersal of species is a fundamental ecological process in the evolution and maintenance of biodiversity. Limited control over ecological parameters has hindered progress in understanding of what enables species to colonize new areas, as well as the importance of interspecies interactions. Such control is necessary to construct reliable mathematical models of ecosystems. In our work, we studied dispersal in the context of bacterial range expansions and identified the major determinants of species coexistence for a bacterial model system of three Escherichia coli strains (toxin-producing, sensitive and resistant). Genetic engineering allowed us to tune strain growth rates and to design different ecological scenarios (cyclic and hierarchical). We found that coexistence of all strains depended on three strongly interdependent factors: composition of inoculum, relative strain growth rates and effective toxin range. Robust agreement between our experiments and a thoroughly calibrated computational model enabled us to extrapolate these intricate interdependencies in terms of phenomenological biodiversity laws. Our mathematical analysis also suggested that cyclic dominance between strains is not a prerequisite for coexistence in competitive range expansions. Instead, robust three-strain coexistence required a balance between growth rates and either a reduced initial ratio of the toxin-producing strain, or a sufficiently short toxin range.
    Full-text · Article · Apr 2014 · Journal of The Royal Society Interface
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