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  1. Article ; Online: Plasmid-free cheater cells commonly evolve during laboratory growth.

    Bedore, Amber M / Waters, Christopher M

    Applied and environmental microbiology

    2024  Volume 90, Issue 4, Page(s) e0231123

    Abstract: It has been nearly a century since the isolation and use of penicillin, heralding the discovery of a wide range of different antibiotics. In addition to clinical applications, such antibiotics have been essential laboratory tools, allowing for selection ... ...

    Abstract It has been nearly a century since the isolation and use of penicillin, heralding the discovery of a wide range of different antibiotics. In addition to clinical applications, such antibiotics have been essential laboratory tools, allowing for selection and maintenance of laboratory plasmids that encode cognate resistance genes. However, antibiotic resistance mechanisms can additionally function as public goods. For example, extracellular beta-lactamases produced by resistant cells that subsequently degrade penicillin and related antibiotics allow neighboring plasmid-free susceptible bacteria to survive antibiotic treatment. How such cooperative mechanisms impact selection of plasmids during experiments in laboratory conditions is poorly understood. Here, we show in multiple bacterial species that the use of plasmid-encoded beta-lactamases leads to significant curing of plasmids in surface-grown bacteria. Furthermore, such curing was also evident for aminoglycoside phosphotransferase and tetracycline antiporter resistance mechanisms. Alternatively, antibiotic selection in liquid growth led to more robust plasmid maintenance, although plasmid loss was still observed. The net outcome of such plasmid loss is the generation of a heterogenous population of plasmid-containing and plasmid-free cells, leading to experimental confounds that are not widely appreciated.IMPORTANCEPlasmids are routinely used in microbiology as readouts of cell biology or tools to manipulate cell function. Central to these studies is the assumption that all cells in an experiment contain the plasmid. Plasmid maintenance in a host cell typically depends on a plasmid-encoded antibiotic resistance marker, which provides a selective advantage when the plasmid-containing cell is grown in the presence of antibiotic. Here, we find that growth of plasmid-containing bacteria on a surface and to a lesser extent in liquid culture in the presence of three distinct antibiotic families leads to the evolution of a significant number of plasmid-free cells, which rely on the resistance mechanisms of the plasmid-containing cells. This process generates a heterogenous population of plasmid-free and plasmid-containing bacteria, an outcome which could confound further experimentation.
    MeSH term(s) Humans ; Plasmids/genetics ; Anti-Bacterial Agents/pharmacology ; Bacteria/genetics ; beta-Lactamases/genetics ; Penicillins/pharmacology
    Chemical Substances Anti-Bacterial Agents ; beta-Lactamases (EC 3.5.2.6) ; Penicillins
    Language English
    Publishing date 2024-03-06
    Publishing country United States
    Document type Journal Article
    ZDB-ID 223011-2
    ISSN 1098-5336 ; 0099-2240
    ISSN (online) 1098-5336
    ISSN 0099-2240
    DOI 10.1128/aem.02311-23
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Plasmid-free cheater cells commonly evolve during laboratory growth.

    Bedore, Amber M / Waters, Christopher M

    bioRxiv : the preprint server for biology

    2023  

    Abstract: It has been nearly a century since the isolation and use of penicillin, heralding the discovery of a wide range of different antibiotics. In addition to clinical applications, such antibiotics have been essential laboratory tools, allowing for selection ... ...

    Abstract It has been nearly a century since the isolation and use of penicillin, heralding the discovery of a wide range of different antibiotics. In addition to clinical applications, such antibiotics have been essential laboratory tools, allowing for selection and maintenance of laboratory plasmids that encode cognate resistance genes. However, antibiotic resistance mechanisms can additionally function as public goods. For example, secretion of beta-lactamase from resistant cells, and subsequent degradation of nearby penicillin and related antibiotics, allows neighboring plasmid-free susceptible bacteria to survive antibiotic treatment. How such cooperative mechanisms impact selection of plasmids during experiments in laboratory conditions is poorly understood. Here, we show that the use of plasmid-encoded beta-lactamases leads to significant curing of plasmids in surface grown bacteria. Furthermore, such curing was also evident for aminoglycoside phosphotransferase and tetracycline antiporter resistance mechanisms. Alternatively, antibiotic selection in liquid growth led to more robust plasmid maintenance, although plasmid loss still occurred. The net outcome of such plasmid loss is the generation of a heterogenous population of plasmid-containing and plasmid-free cells, leading to experimental confounds that are not widely appreciated.
    Language English
    Publishing date 2023-05-20
    Publishing country United States
    Document type Preprint
    DOI 10.1101/2023.05.19.541508
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Replication cycle timing determines phage sensitivity to a cytidine deaminase toxin/antitoxin bacterial defense system.

    Hsueh, Brian Y / Ferrell, Micah J / Sanath-Kumar, Ram / Bedore, Amber M / Waters, Christopher M

    PLoS pathogens

    2023  Volume 19, Issue 9, Page(s) e1011195

    Abstract: Toxin-antitoxin (TA) systems are ubiquitous two-gene loci that bacteria use to regulate cellular processes such as phage defense. Here, we demonstrate the mechanism by which a novel type III TA system, avcID, is activated and confers resistance to phage ... ...

    Abstract Toxin-antitoxin (TA) systems are ubiquitous two-gene loci that bacteria use to regulate cellular processes such as phage defense. Here, we demonstrate the mechanism by which a novel type III TA system, avcID, is activated and confers resistance to phage infection. The toxin of the system (AvcD) is a deoxycytidylate deaminase that converts deoxycytidines (dC) to dexoyuridines (dU), while the RNA antitoxin (AvcI) inhibits AvcD activity. We have shown that AvcD deaminated dC nucleotides upon phage infection, but the molecular mechanism that activated AvcD was unknown. Here we show that the activation of AvcD arises from phage-induced inhibition of host transcription, leading to degradation of the labile AvcI. AvcD activation and nucleotide depletion not only decreases phage replication but also increases the formation of defective phage virions. Surprisingly, infection of phages such as T7 that are not inhibited by AvcID also lead to AvcI RNA antitoxin degradation and AvcD activation, suggesting that depletion of AvcI is not sufficient to confer protection against some phage. Rather, our results support that phage with a longer replication cycle like T5 are sensitive to AvcID-mediated protection while those with a shorter replication cycle like T7 are resistant.
    MeSH term(s) Cytidine Deaminase ; Antitoxins ; Bacteria ; Bacteriophages/genetics ; Nucleotides ; RNA
    Chemical Substances Cytidine Deaminase (EC 3.5.4.5) ; Antitoxins ; Nucleotides ; RNA (63231-63-0)
    Language English
    Publishing date 2023-09-08
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 2205412-1
    ISSN 1553-7374 ; 1553-7374
    ISSN (online) 1553-7374
    ISSN 1553-7374
    DOI 10.1371/journal.ppat.1011195
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Time to lysis determines phage sensitivity to a cytidine deaminase toxin/antitoxin bacterial defense system.

    Hsueh, Brian Y / Sanath-Kumar, Ram / Bedore, Amber M / Waters, Christopher M

    bioRxiv : the preprint server for biology

    2023  

    Abstract: Toxin-antitoxin (TA) systems are ubiquitous two-gene loci that bacteria use to regulate cellular processes such as phage defense. Here, we demonstrate the mechanism by which a novel type III TA system, : Author’s summary: Numerous diverse antiphage ... ...

    Abstract Toxin-antitoxin (TA) systems are ubiquitous two-gene loci that bacteria use to regulate cellular processes such as phage defense. Here, we demonstrate the mechanism by which a novel type III TA system,
    Author’s summary: Numerous diverse antiphage defense systems have been discovered in the past several years, but the mechanisms of how these systems are activated upon phage infection and why these systems protect against some phage but not others are poorly understood. The AvcID toxin-antitoxin phage defense system depletes nucleotides of the dC pool inside the host upon phage infection. We show that phage inhibition of host cell transcription activates this system by depleting the AvcI inhibitory sRNA, which inhibits production of phage and leads to the formation of defective virions. Additionally, we determined that phage lysis time is a key factor that influences sensitivity to AvcID with faster replicating phage exhibiting resistance to its effects. This study has implications for understanding the factors that influence bacterial host/phage dynamics.
    Language English
    Publishing date 2023-02-10
    Publishing country United States
    Document type Preprint
    DOI 10.1101/2023.02.09.527960
    Database MEDical Literature Analysis and Retrieval System OnLINE

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