A phylogenetic approach to assessing the targets of microbial warfare

Riley, Margaret A.; Goldstone, Carla; Wertz, John E.; Gordon, David M.

doi:10.1046/j.1420-9101.2003.00575.x

Cited by 69 publications

(82 citation statements)

References 44 publications

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“…Bacteriocins are a diverse group of antimicrobial toxins that are produced by all species of bacteria (Riley & Wertz, 2002;Riley et al, 2003). Unlike traditional broad-spectrum antibiotics, bacteriocins have a narrow killing range and are generally only toxic to susceptible strains of the same or a closely related species (Riley & Wertz, 2002).…”

Section: Introductionmentioning

confidence: 99%

Evolution of colicin BM plasmids: the loss of the colicin B activity gene

Christenson

Gordon

2009

Microbiology

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Colicins, a class of antimicrobial compounds produced by bacteria, are thought to be important mediators of intra-and interspecific interactions, and are a significant factor in maintaining microbial diversity. Colicins B and M are among the most common colicins produced by Escherichia coli, and are usually encoded adjacently on the same plasmid. In this study, the characterization of a collection of E. coli isolated from Australian vertebrates revealed that a significant fraction of colicin BM strains lack an intact colicin B activity gene. The colicin B and M gene region was sequenced in 60 strains and it was found (with one exception) that all plasmids lacking an intact colicin B activity gene have an identical colicin gene structure, possessing a complete colicin B immunity gene and a 130 bp remnant of the B activity gene. A phylogenetic analysis of the colicin M and B operons and characterization of the plasmids suggested that ColBM plasmids with a truncated B activity gene have evolved on at least three separate occasions. Colicin B immunity was found to be non-functional in strains that have lost colicin B activity, and colicin M was still produced despite the absence of the SOS box believed to regulate its production in colicin BM strains. The presence of a remnant of the microcin V operon next to the truncated colicin B activity gene indicated that these plasmids evolved as a consequence of gene transfer between colicin BM and microcin V plasmids. We suggest that these transfer events most likely involved the transfer of some microcin V genes and associated virulence factors onto ColBM plasmids.

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Section: Introductionmentioning

confidence: 99%

Evolution of colicin BM plasmids: the loss of the colicin B activity gene

Christenson

Gordon

2009

Microbiology

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“…They are a diverse family of proteins with a range of antimicrobial killing activities including enzyme inhibition, nuclease activity and pore formation in cell membranes (Riley & Wertz 2002). Unlike other antimicrobials, the lethal activity of bacteriocins is often (but not always) limited to members of the same or closely related species to the producer (Riley et al 2003), suggesting a major role in competition with conspecifics. Clone mates are protected from the toxic effects of bacteriocins as a result of genetic linkage between the bacteriocin gene and an immunity gene that encodes a factor that deactivates the bacteriocin (Riley & Wertz 2002).…”

Section: Introductionmentioning

confidence: 99%

Interference competition and parasite virulence

Massey

Buckling

ffrench‐Constant

2004

Proc. R. Soc. Lond. B

100

111

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Within-host competition between parasites, a consequence of infection by multiple strains, is predicted to favour rapid host exploitation and greater damage to hosts (virulence). However, the inclusion of biological variables can drastically change this relationship. For example, if competing parasite strains produce toxins that kill each other (interference competition), their growth rates and virulence may be reduced relative to single-strain infections. Bacteriocins are antimicrobial toxins produced by bacteria that target closely related strains and species, and to which the producing strain is immune. We investigated competition between bacteriocin-producing, insect-killing bacteria (Photorhabdus and Xenorhabdus) and how this competition affected virulence in caterpillars. Where one strain could kill the other, and not vice versa, the non-killing strain was competitively excluded, and insect mortality was the same as that of the killing strain alone. However, when caterpillars were multiply infected by strains that could kill each other, we did not observe competitive exclusion and their virulence was less than single-strain infections. The ubiquity and diversity of bacteriocins among pathogenic bacteria suggest mixed infections will be, on average, less virulent than single infections.

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“…Bacteriocins are a group of polypeptide antibiotics excreted by different bacterial genera including Gram-negative and Gram-positive species (1)(2)(3). Once released, they restrain the growth of competing bacterial strains in a receptor-mediated manner employing several mechanisms.…”

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confidence: 99%

Microcin Amyloid Fibrils A Are Reservoir of Toxic Oligomeric Species

Shahnawaz

Soto

2012

Journal of Biological Chemistry

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Microcin E492 (Mcc), a low molecular weight bacteriocin produced by Klebsiella pneumoniae RYC492, has been shown to exist in two forms: soluble forms that are believed to be toxic to the bacterial cell by forming pores and non-toxic fibrillar forms that share similar biochemical and biophysical properties with amyloids associated with several human diseases. Here we report that fibrils polymerized in vitro from soluble forms sequester toxic species that can be released upon changing environmental conditions such as pH, ionic strength, and upon dilution. Our results indicate that basic pH (>8.5), low NaCl concentrations (<50 mM), and dilution (>10-fold) destabilize Mcc fibrils into more soluble species that are found to be toxic to the target cells. Additionally, we also found a similar conversion of non-toxic fibrils into highly toxic oligomers using Mcc aggregates produced in vivo. Moreover, the soluble protein released from fibrils is able to rapidly polymerize into amyloid fibrils under fibril-forming conditions and to efficiently seed aggregation of monomeric Mcc. Our findings indicate that fibrillar forms of Mcc constitute a reservoir of toxic oligomeric species that is released into the medium upon changing the environmental conditions. These findings may have substantial implications to understand the dynamic process of interconversion between toxic and non-toxic aggregated species implicated in protein misfolding diseases.Bacteriocins are a group of polypeptide antibiotics excreted by different bacterial genera including Gram-negative and Gram-positive species (1-3). Once released, they restrain the growth of competing bacterial strains in a receptor-mediated manner employing several mechanisms. Mcc 2 is a low molecular weight (ϳ7.8 kDa) bacteriocin produced by Klebsiella pneumoniae RYC492 (4 -6). Antibacterial activity of Mcc appeared to be restricted to the Enterobacteriaceae species, closely related to the producer strain that directly competes with Klebsiella to occupy a spatial niche in the ecosystem (5, 7). Mcc has been shown to exert its toxic effect by forming ion channels on the cell membrane of target cells in a receptor-mediated fashion, which leads to a rapid depolarization and thus permeabilization of the cell membrane (6,8,9). Unlike other bacteriocins, toxic forms of Mcc are produced mainly in the exponential phase and comparatively less toxic in the stationary phase (5, 10). Surprisingly, neither apparent differences in the amounts of Mcc nor degradation or post-translational modifications have been shown to be responsible for the loss of activity (11). Some reports have described that these changes in Mcc toxicity may be due to the production of a microcin antagonist known as enterochelin in the stationary phase (12). More recently, the loss of Mcc toxicity in the stationary phase has been attributed to changes in the folding and polymerization of Mcc into aggregated structures similar to amyloid fibrils (13). Compelling in vitro and in vivo studies have shown that the changes on the Mcc...

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A phylogenetic approach to assessing the targets of microbial warfare

Cited by 69 publications

References 44 publications

Evolution of colicin BM plasmids: the loss of the colicin B activity gene

Evolution of colicin BM plasmids: the loss of the colicin B activity gene

Interference competition and parasite virulence

Microcin Amyloid Fibrils A Are Reservoir of Toxic Oligomeric Species

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