scholarly journals Listeria Phage and Phage Tail Induction Triggered by Components of Bacterial Growth Media (Phosphate, LiCl, Nalidixic Acid, and Acriflavine)

2015 ◽  
Vol 81 (6) ◽  
pp. 2117-2124 ◽  
Author(s):  
Jean-Paul Lemaître ◽  
Amandine Duroux ◽  
Romain Pimpie ◽  
Jean-Marie Duez ◽  
Marie-Louise Milat
Keyword(s):  
Listeria Monocytogenes ◽  
Nalidixic Acid ◽  
Bacterial Growth ◽  
False Negative ◽  
Brain Heart Infusion ◽  
False Negative Result ◽  
Growth Media ◽  
Content Type ◽  
Phage Tail ◽  
Initial Ph

ABSTRACTThe detection ofListeria monocytogenesfrom food is currently carried out using a double enrichment. For the ISO methodology, this double enrichment is performed using half-Fraser and Fraser broths, in which the overgrowth ofL. innocuacan occur in samples where both species are present. In this study, we analyzed the induction of phages and phage tails ofListeriaspp. in these media and in two brain heart infusion (BHI) broths (BHIM [bioMérieux] and BHIK [Biokar]) to identify putative effectors. It appears that Na2HPO4at concentrations ranging from 1 to 40 g/liter with an initial pH of 7.5 can induce phage or phage tail production ofListeriaspp., especially with 10 g/liter of Na2HPO4and a pH of 7.5, conditions present in half-Fraser and Fraser broths. Exposure to LiCl in BHIM (18 to 21 g/liter) can also induce phage and phage tail release, but in half-Fraser and Fraser broths, the concentration of LiCl is much lower (3 g/liter). Low phage titers were induced by acriflavine and/or nalidixic acid. We also show that the production of phages and phage tails can occur in half-Fraser and Fraser broths. This study points out that induction of phages and phage tails could be triggered by compounds present in enrichment media. This could lead to a false-negative result for the detection ofL. monocytogenesin food products.

scholarly journals Nisin Resistance of Listeria monocytogenes Is Increased by Exposure to Salt Stress and Is Mediated via LiaR

2013 ◽  
Vol 79 (18) ◽  
pp. 5682-5688 ◽  
Author(s):  
Teresa M. Bergholz ◽  
Silin Tang ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Salt Stress ◽  
Listeria Monocytogenes ◽  
Safety Concern ◽  
Response Regulator ◽  
Brain Heart Infusion ◽  
Control Measures ◽  
Protective Effects ◽  
Wild Type ◽  
Content Type ◽  
Type Strains

ABSTRACTGrowth ofListeria monocytogeneson refrigerated, ready-to-eat food is a significant food safety concern. Natural antimicrobials, such as nisin, can be used to control this pathogen on food, but little is known about how other food-related stresses may impact how the pathogen responds to these compounds. Prior work demonstrated that exposure ofL. monocytogenesto salt stress at 7°C led to increased expression of genes involved in nisin resistance, including the response regulatorliaR. We hypothesized that exposure to salt stress would increase subsequent resistance to nisin and that LiaR would contribute to increased nisin resistance. Isogenic deletion mutations inliaRwere constructed in 7 strains ofL. monocytogenes, and strains were exposed to 6% NaCl in brain heart infusion broth and then tested for resistance to nisin (2 mg/ml Nisaplin) at 7°C. For the wild-type strains, exposure to salt significantly increased subsequent nisin resistance (P< 0.0001) over innate levels of resistance. Compared to the salt-induced nisin resistance of wild-type strains, ΔliaRstrains were significantly more sensitive to nisin (P< 0.001), indicating that induction of LiaFSR led to cross-protection ofL. monocytogenesagainst subsequent inactivation by nisin. Transcript levels of LiaR-regulated genes were induced by salt stress, and lmo1746 andtelAwere found to contribute to LiaR-mediated salt-induced nisin resistance. These data suggest that environmental stresses similar to those on foods can influence the resistance ofL. monocytogenesto antimicrobials such as nisin, and potential cross-protective effects should be considered when selecting and applying control measures for this pathogen on ready-to-eat foods.

scholarly journals Cyclic di-AMP Is Critical for Listeria monocytogenes Growth, Cell Wall Homeostasis, and Establishment of Infection

mBio ◽  
2013 ◽  
Vol 4 (3) ◽  
Author(s):  
Chelsea E. Witte ◽  
Aaron T. Whiteley ◽  
Thomas P. Burke ◽  
John-Demian Sauer ◽  
Daniel A. Portnoy ◽  
...  
Keyword(s):  
Cell Wall ◽  
Listeria Monocytogenes ◽  
Bacterial Growth ◽  
Genetic Screen ◽  
Content Type ◽  
Forward Genetic Screen ◽  
Innate Immune Signaling ◽  
Food Borne Illness ◽  
Multidrug Resistance Transporters

ABSTRACT Listeria monocytogenes infection leads to robust induction of an innate immune signaling pathway referred to as the cytosolic surveillance pathway (CSP), characterized by expression of beta interferon (IFN-β) and coregulated genes. We previously identified the IFN-β stimulatory ligand as secreted cyclic di-AMP. Synthesis of c-di-AMP in L. monocytogenes is catalyzed by the diadenylate cyclase DacA, and multidrug resistance transporters are necessary for secretion. To identify additional bacterial factors involved in L. monocytogenes detection by the CSP, we performed a forward genetic screen for mutants that induced altered levels of IFN-β. One mutant that stimulated elevated levels of IFN-β harbored a transposon insertion in the gene lmo0052. Lmo0052, renamed here PdeA, has homology to a cyclic di-AMP phosphodiesterase, GdpP (formerly YybT), of Bacillus subtilis and is able to degrade c-di-AMP to the linear dinucleotide pApA. Reduction of c-di-AMP levels by conditional depletion of the di-adenylate cyclase DacA or overexpression of PdeA led to marked decreases in growth rates, both in vitro and in macrophages. Additionally, mutants with altered levels of c-di-AMP had different susceptibilities to peptidoglycan-targeting antibiotics, suggesting that the molecule may be involved in regulating cell wall homeostasis. During intracellular infection, increases in c-di-AMP production led to hyperactivation of the CSP. Conditional depletion of dacA also led to increased IFN-β expression and a concomitant increase in host cell pyroptosis, a result of increased bacteriolysis and subsequent bacterial DNA release. These data suggest that c-di-AMP coordinates bacterial growth, cell wall stability, and responses to stress and plays a crucial role in the establishment of bacterial infection. IMPORTANCE Listeria monocytogenes is a Gram-positive intracellular pathogen and the causative agent of the food-borne illness listeriosis. Upon infection, L. monocytogenes stimulates expression of IFN-β and coregulated genes dependent upon host detection of a secreted bacterial signaling nucleotide, c-di-AMP. Using a forward genetic screen for mutants that induced high levels of host IFN-β expression, we identified a c-di-AMP phosphodiesterase, PdeA, that degrades c-di-AMP. Here we characterize L. monocytogenes mutants that express enhanced or diminished levels of c-di-AMP. Decreased c-di-AMP levels by conditional depletion of the diadenylate cyclase (DacA) or overexpression of PdeA attenuated bacterial growth and led to bacteriolysis, suggesting that its production is essential for viability and may regulate cell wall metabolism. Mutants lacking PdeA had a distinct transcriptional profile, which may provide insight into additional roles for the molecule. This work demonstrates that c-di-AMP is a critical signaling molecule required for bacterial replication, cell wall stability, and pathogenicity.

scholarly journals Secretion Chaperones PrsA2 and HtrA Are Required for Listeria monocytogenes Replication following Intracellular Induction of Virulence Factor Secretion

2016 ◽  
Vol 84 (10) ◽  
pp. 3034-3046 ◽  
Author(s):  
Jana K. Ahmed ◽  
Nancy E. Freitag
Keyword(s):  
Listeria Monocytogenes ◽  
Virulence Factor ◽  
Bacterial Growth ◽  
Cell Types ◽  
Broth Culture ◽  
Bacterial Invasion ◽  
Bacterial Membrane ◽  
Content Type ◽  
Factor Secretion

The Gram-positive bacteriumListeria monocytogenestransitions from an environmental organism to an intracellular pathogen following its ingestion by susceptible mammalian hosts. Bacterial replication within the cytosol of infected cells requires activation of the central virulence regulator PrfA followed by a PrfA-dependent induction of secreted virulence factors. The PrfA-induced secreted chaperone PrsA2 and the chaperone/protease HtrA contribute to the folding and stability of select proteins translocated across the bacterial membrane.L. monocytogenesstrains that lack bothprsA2andhtrAexhibit near-normal patterns of growth in broth culture but are severely attenuatedin vivo. We hypothesized that, in the absence of PrsA2 and HtrA, the increase in PrfA-dependent protein secretion that occurs following bacterial entry into the cytosol results in misfolded proteins accumulating at the bacterial membrane with a subsequent reduction in intracellular bacterial viability. Consistent with this hypothesis, the introduction of a constitutively activated allele ofprfA(prfA*) into ΔprsA2ΔhtrAstrains was found to essentially inhibit bacterial growth at 37°C in broth culture. ΔprsA2ΔhtrAstrains were additionally found to be defective for cell invasion and vacuole escape in selected cell types, steps that precede full PrfA activation. These data establish the essential requirement for PrsA2 and HtrA in maintaining bacterial growth under conditions of PrfA activation. In addition, chaperone function is required for efficient bacterial invasion and rapid vacuole lysis within select host cell types, indicating roles for PrsA2/HtrA prior to cytosolic PrfA activation and the subsequent induction of virulence factor secretion.

scholarly journals Intracellular Accumulation of High Levels of γ-Aminobutyrate by Listeria monocytogenes 10403S in Response to Low pH: Uncoupling of γ-Aminobutyrate Synthesis from Efflux in a Chemically Defined Medium

2010 ◽  
Vol 76 (11) ◽  
pp. 3529-3537 ◽  
Author(s):  
Kimon-Andreas G. Karatzas ◽  
Orla Brennan ◽  
Sin�ad Heavin ◽  
John Morrissey ◽  
Conor P. O'Byrne
Keyword(s):  
Listeria Monocytogenes ◽  
Brain Heart Infusion ◽  
Defined Medium ◽  
Low Ph ◽  
Growth Media ◽  
Chemically Defined Medium ◽  
Extracellular Glutamate ◽  
Gaba Production ◽  
Mammalian Stomach ◽  
Acidic Conditions

ABSTRACT It is well established that the glutamate decarboxylase (GAD) system is central to the survival of Listeria monocytogenes at low pH, both in acidic foods and within the mammalian stomach. The accepted model proposes that under acidic conditions extracellular glutamate is transported into the cell in exchange for an intracellular γ-aminobutyrate (GABAi). The glutamate is then decarboxylated to GABAi, a reaction that consumes a proton, thereby helping to prevent acidification of the cytoplasm. In this study, we show that glutamate supplementation had no influence on either growth rate at pH 5.0 or survival at pH 2.5 when L. monocytogenes 10403S was grown in a chemically defined medium (DM). In response to acidification, cells grown in DM failed to efflux GABA, even when glutamate was added to the medium. In contrast, in brain heart infusion (BHI), the same strain produced significant extracellular GABA (GABAe) in response to acidification. In addition, high levels of GABAi (>80 mM) were found in the cytoplasm in response to low pH in both growth media. Medium-swap and medium-mixing experiments revealed that the GABA efflux apparatus was nonfunctional in DM, even when glutamate was present. It was also found that the GadT2D2 antiporter/decarboxylase system was transcribed poorly in DM-grown cultures while overexpression of gadD1T1 and gadD3 occurred in response to pH 3.5. Interestingly, BHI-grown cells did not respond with upregulation of any of the GAD system genes when challenged at pH 3.5. The accumulation of GABAi in cells grown in DM in the absence of extracellular glutamate indicates that intracellular glutamate is the source of the GABAi. These results demonstrate that GABA production can be uncoupled from GABA efflux, a finding that alters the way we should view the operation of bacterial GAD systems.

scholarly journals Unveiling the Expression Characteristics of IspC, a Cell Wall-Associated Peptidoglycan Hydrolase in Listeria monocytogenes, during Growth under Stress Conditions

2012 ◽  
Vol 78 (22) ◽  
pp. 7833-7840 ◽  
Author(s):  
Jennifer Ronholm ◽  
Xudong Cao ◽  
Min Lin
Keyword(s):  
Listeria Monocytogenes ◽  
Diagnostic Marker ◽  
Stress Conditions ◽  
Health Concern ◽  
Immunofluorescent Staining ◽  
Clinical Samples ◽  
Peptidoglycan Hydrolase ◽  
Growth Media ◽  
Content Type ◽  
Serotype 4B

ABSTRACTListeria monocytogenesserotype 4b is a food-borne pathogen of public health concern, since it accounts for approximately 40% of human listeriosis cases. We have recently identified IspC, a surface-localized peptidoglycan hydrolase, as the antigen recognized by a number of monoclonal antibodies (MAbs) produced against a serotype 4b strain for diagnostic applications. To determine whether IspC, which is well conserved among various serotype 4b strains, is a useful diagnostic marker in antibody-based methods, we assessed the expression of IspC inL. monocytogenescultured under normal and stress conditions. A functional promoter directing the transcription of theispCgene was identified upstream of theispCopen reading frame by constructing a promoterlesslacZgene fusion with the putativeispCpromoter region and by 5′ rapid amplification of cDNA ends analysis. Using both thelacZreporter gene system and immunofluorescent staining with an IspC-specific MAb, we provide evidence that IspC is expressed on the cell surface in all growth conditions tested (temperature, osmotic stress, pH, ethanol, oxidative stress, anaerobic conditions, carbon source, and type of growth media) that allow for cellular division, although the level ofispCgene expression varies. These results demonstrated the usefulness of IspC as an excellent diagnostic marker for the serotype 4b strains and imply that IspC, in conjunction with specific MAbs, can be targeted for detection and isolation ofL. monocytogenesserotype 4b strains directly from food, environmental, and clinical samples with minimal or no need for culture enrichment.

scholarly journals Transcriptomic Analysis of the Adaptation of Listeria monocytogenes to Growth on Vacuum-Packed Cold Smoked Salmon

2015 ◽  
Vol 81 (19) ◽  
pp. 6812-6824 ◽  
Author(s):  
Silin Tang ◽  
Renato H. Orsi ◽  
Henk C. den Bakker ◽  
Martin Wiedmann ◽  
Kathryn J. Boor ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Molecular Mechanisms ◽  
Growth Parameters ◽  
Differential Expression Analysis ◽  
Foodborne Pathogen ◽  
Brain Heart Infusion ◽  
Enrichment Analysis ◽  
Water Phase ◽  
Content Type ◽  
Smoked Salmon

ABSTRACTThe foodborne pathogenListeria monocytogenesis able to survive and grow in ready-to-eat foods, in which it is likely to experience a number of environmental stresses due to refrigerated storage and the physicochemical properties of the food. Little is known about the specific molecular mechanisms underlying survival and growth ofL. monocytogenesunder different complex conditions on/in specific food matrices. Transcriptome sequencing (RNA-seq) was used to understand the transcriptional landscape ofL. monocytogenesstrain H7858 grown on cold smoked salmon (CSS; water phase salt, 4.65%; pH 6.1) relative to that in modified brain heart infusion broth (MBHIB; water phase salt, 4.65%; pH 6.1) at 7°C. Significant differential transcription of 149 genes was observed (false-discovery rate [FDR], <0.05; fold change, ≥2.5), and 88 and 61 genes were up- and downregulated, respectively, in H7858 grown on CSS relative to the genes in H7858 grown in MBHIB. In spite of these differences in transcriptomes under these two conditions, growth parameters forL. monocytogeneswere not significantly different between CSS and MBHIB, indicating that the transcriptomic differences reflect howL. monocytogenesis able to facilitate growth under these different conditions. Differential expression analysis and Gene Ontology enrichment analysis indicated that genes encoding proteins involved in cobalamin biosynthesis as well as ethanolamine and 1,2-propanediol utilization have significantly higher transcript levels in H7858 grown on CSS than in that grown in MBHIB. Our data identify specific transcriptional profiles ofL. monocytogenesgrowing on vacuum-packaged CSS, which may provide targets for the development of novel and improved strategies to controlL. monocytogenesgrowth on this ready-to-eat food.

scholarly journals Listeria monocytogenes Mutants with Altered Growth Phenotypes at Refrigeration Temperature and High Salt Concentrations

2011 ◽  
Vol 78 (4) ◽  
pp. 1265-1272 ◽  
Author(s):  
Laurel S. Burall ◽  
Pongpan Laksanalamai ◽  
Atin R. Datta
Keyword(s):  
Listeria Monocytogenes ◽  
Substantial Reduction ◽  
Brain Heart Infusion ◽  
High Salt ◽  
Salt Adaptation ◽  
Content Type ◽  
Transposon Insertion ◽  
Food Isolate ◽  
Transposon Mutants ◽  
Growth Profiles

ABSTRACTListeria monocytogenescan survive and grow in refrigerated temperatures and high-salt environments. In an effort to better understand the associated mechanisms, a library of ∼ 5,200 transposon mutants of LS411, a food isolate from the Jalisco cheese outbreak, were screened for their ability to grow in brain heart infusion (BHI) broth at 5°C or in the presence of 7% NaCl and two mutants with altered growth profiles were identified. The LS522 mutant has a transposon insertion betweensecA2andiapand showed a significant reduction in growth in BHI broth at 5°C and in the presence of 7% NaCl. Reverse transcriptase quantitative PCR (RT-qPCR) revealed a substantial reduction in the expression ofiap. Additionally, a hypothetical gene (met), containing a putativeS-adenosylmethionine-dependent methyltransferase domain, downstream ofiaphad downregulated expression. In-frame deletion mutants ofiapandmetwere created in LS411. The LS560 (LS411Δiap) mutant showed reduced growth at 5°C and in the presence of 7% salt, confirming its role in cold and salt growth attenuation. Surprisingly, the LS655 (LS411 Δmet) mutant showed slightly increased growth during refrigeration, though no alteration was seen in salt growth relative to the wild-type strain. The LS527 mutant, containing an insertion 36 bp upstream of thegbuoperon, showed reduced expression of thegbutranscript by RT-qPCR and also showed growth reduction at 5°C and in the presence of 7% salt. This attenuation was severely exacerbated when the mutant was grown under the combined stresses. Analysis of thegbuoperon deletion mutant showed decreased growth in 7% salt and refrigeration, supporting the previously characterized role for this gene in cold and salt adaptation. These studies indicate the potential for an intricate relationship between environmental stress regulation and virulence inL. monocytogenes.

scholarly journals Glucose and Nutrient Concentrations Affect the Expression of a 104-Kilodalton Listeria Adhesion Protein in Listeria monocytogenes

2002 ◽  
Vol 68 (10) ◽  
pp. 4876-4883 ◽  
Author(s):  
Ziad W. Jaradat ◽  
Arun K. Bhunia
Keyword(s):  
Listeria Monocytogenes ◽  
Brain Heart Infusion ◽  
Luria Bertani ◽  
Nutrient Concentrations ◽  
Enzyme Linked Immunosorbent Assay ◽  
Growth Media ◽  
Adhesion Protein ◽  
Sugar Fermentation ◽  
Rich Media ◽  
High Concentrations

ABSTRACT Growth media and environmental conditions influence the expression of adhesion and invasion proteins in Listeria monocytogenes. Here, the expression of the 104-kDa Listeria adhesion protein (LAP) was studied in nutrient-rich media (Trypticase soy broth [TSB] and brain heart infusion [BHI]), minimal medium (Luria-Bertani [LB]), or nutrient-deficient medium (peptone water [PW]) by immunoblotting, enzyme-linked immunosorbent assay (ELISA), and immunoelectron microscopy. Also, the effect of incorporating different concentrations of glucose on LAP expression was studied. Immunoblotting showed that LAP expression was at least twofold higher in LB medium than in TSB or BHI, while PW supported very poor cell growth and LAP expression. ELISA and immunoblotting results showed that higher concentrations of glucose (>1.6 g/liter) lowered the culture pH and suppressed LAP expression by more than 75%; however, the addition of K2HPO4 reduced this effect. L. monocytogenes cells grown in LB media with lower concentrations of glucose showed higher adhesion to Caco-2 cells (3,716 and 4,186 cpm of attached bacteria for 0 and 0.2 g of glucose/liter, respectively), while L. monocytogenes cells grown in LB with higher glucose concentrations exhibited lower adhesion (2,126 and 2,221 cpm for 1.6 and 3.2 g of glucose/liter, respectively). A LAP-negative L. monocytogenes strain (A572) showed low adhesion profiles regardless of the amount of glucose added. Transmission electron microscopy revealed that LAP is localized mainly in the cytoplasm, with only a few molecules located on the cell surface. Growth in LB with high glucose (3.2 g/liter) showed the presence of only a few molecules in the cells, corroborating the results observed with ELISA or immunoblotting. In summary, nutrient-rich media and high concentrations of glucose suppressed LAP expression, which possibly is due to the changes in the pH of the media during growth from the accumulation of sugar fermentation by-products.

scholarly journals Role of GlnR in Controlling Expression of Nitrogen Metabolism Genes in Listeria monocytogenes

2020 ◽  
Vol 202 (19) ◽  
Author(s):  
Rajesh Biswas ◽  
Abraham L. Sonenshein ◽  
Boris R. Belitsky
Keyword(s):  
Listeria Monocytogenes ◽  
Nitrogen Metabolism ◽  
Transcriptional Regulator ◽  
Nitrogen Sources ◽  
Negative Regulator ◽  
Ammonium Uptake ◽  
Ammonium Transport ◽  
Growth Media ◽  
Content Type

ABSTRACT Listeria monocytogenes is a fastidious bacterial pathogen that can utilize only a limited number of nitrogen sources for growth. Both glutamine and ammonium are common nitrogen sources used in listerial defined growth media, but little is known about the regulation of their uptake or utilization. The functional role of L. monocytogenes GlnR, the transcriptional regulator of nitrogen metabolism genes in low-G+C Gram-positive bacteria, was determined using transcriptome sequencing and real-time reverse transcription-PCR experiments. The GlnR regulon included transcriptional units involved in ammonium transport (amtB glnK) and biosynthesis of glutamine (glnRA) and glutamate (gdhA) from ammonium. As in other bacteria, GlnR proved to be an autoregulatory repressor of the glnRA operon. Unexpectedly, GlnR was most active during growth with ammonium as the nitrogen source and less active in the glutamine medium, apparently because listerial cells perceive growth with glutamine as a nitrogen-limiting condition. Therefore, paradoxically, expression of the glnA gene, encoding glutamine synthetase, was highest in the glutamine medium. For the amtB glnK operon, GlnR served as both a negative regulator in the presence of ammonium and a positive regulator in the glutamine medium. The gdhA gene was subject to a third mode of regulation that apparently required an elevated level of GlnR for repression. Finally, activity of glutamate dehydrogenase encoded by the gdhA gene appeared to correlate inversely with expression of gltAB, the operon that encodes the other major glutamate-synthesizing enzyme, glutamate synthase. Both gdhA and amtB were also regulated, in a negative manner, by the global transcriptional regulator CodY. IMPORTANCE L. monocytogenes is a widespread foodborne pathogen. Nitrogen-containing compounds, such as the glutamate-containing tripeptide, glutathione, and glutamine, have been shown to be important for expression of L. monocytogenes virulence genes. In this work, we showed that a transcriptional regulator, GlnR, controls expression of critical listerial genes of nitrogen metabolism that are involved in ammonium uptake and biosynthesis of glutamine and glutamate. A different mode of GlnR-mediated regulation was found for each of these three pathways.

scholarly journals F-Type Bacteriocins of Listeria monocytogenes: a New Class of Phage Tail-Like Structures Reveals Broad Parallel Coevolution between Tailed Bacteriophages and High-Molecular-Weight Bacteriocins

2016 ◽  
Vol 198 (20) ◽  
pp. 2784-2793 ◽  
Author(s):  
Grace Lee ◽  
Urmi Chakraborty ◽  
Dana Gebhart ◽  
Gregory R. Govoni ◽  
Z. Hong Zhou ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Listeria Monocytogenes ◽  
High Molecular Weight ◽  
Genetic Locus ◽  
Severe Disease ◽  
Dna Delivery ◽  
Content Type ◽  
New Class ◽  
Phage Tail ◽  
Rule Out

ABSTRACTListeria monocytogenesis a significant foodborne human pathogen that can cause severe disease in certain high-risk individuals.L. monocytogenesis known to produce high-molecular-weight, phage tail-like bacteriocins, or “monocins,” upon induction of the SOS system. In this work, we purified and characterized monocins and found them to be a new class of F-type bacteriocins. TheL. monocytogenesmonocin genetic locus was cloned and expressed inBacillus subtilis, producing specifically targeted bactericidal particles. The receptor binding protein, which determines target cell specificity, was identified and engineered to change the bactericidal spectrum. Unlike the F-type pyocins ofPseudomonas aeruginosa, which are related to lambda-like phage tails, monocins are more closely related to TP901-1-like phage tails, structures not previously known to function as bacteriocins. Monocins therefore represent a new class of phage tail-like bacteriocins. It appears that multiple classes of phage tails and their related bacteriocins have coevolved separately in parallel.IMPORTANCEPhage tail-like bacteriocins (PTLBs) are structures widespread among the members of the bacterial kingdom that are evolutionarily related to the DNA delivery organelles of phages (tails). We identified and characterized “monocins” ofListeria monocytogenesand showed that they are related to the tail structures of TP901-1-like phages, structures not previously known to function as bacteriocins. Our results show that multiple types of envelope-penetrating machines have coevolved in parallel to function either for DNA delivery (phages) or as membrane-disrupting bacteriocins. While it has commonly been assumed that these structures were coopted from phages, we cannot rule out the opposite possibility, that ancient phages coopted complex bacteriocins from the cell, which then underwent adaptations to become efficient at translocating DNA.

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