Phage Lysis: Multiple Genes for Multiple Barriers

Cahill, Jesse; Young, Ry

doi:10.1016/bs.aivir.2018.09.003

Cited by 221 publications

(208 citation statements)

References 110 publications

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“…Holins are the first step in canonical holin-endolysin-spanin lysis systems for Gram negative bacteria (14,15). To briefly summarize the process, holins accumulate in the inner membrane acting as lysis timers, until they reach a critical concentration that triggers depolarization of the membrane, making holes that enable endolysins to access the peptidoglycan.…”

Section: Introductionmentioning

confidence: 99%

“…While such visually discernable phenotypes enabled early genetic inquiries, the molecular underpinnings of LIN remained unknown until recently and have only been identified and characterized in the T-even coliphages where LIN is mediated by holins and antiholins (11)(12)(13). Holins are the first step in canonical holin-endolysin-spanin lysis systems for Gram negative bacteria (14,15). To briefly summarize the process, holins accumulate in the inner membrane acting as lysis timers, until they reach a critical concentration that triggers depolarization of the membrane, making holes that enable endolysins to access the peptidoglycan.…”

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confidence: 99%

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DominantVibrio choleraephage exhibits lysis inhibition sensitive to disruption by a defensive phage satellite

Hays

Seed

2019

Preprint

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AbstractBacteriophages and their bacterial hosts are locked in a dynamic evolutionary arms race. Phage satellites, selfish genomic islands which exploit both host bacterium and target phage, further complicate the evolutionary fray. One such tripartite system involves the etiological agent of the diarrheal disease cholera – Vibrio cholerae, the predominant phage isolated from cholera patients – ICP1, and a phage satellite – PLE. When ICP1 infects V. cholerae harboring the integrated PLE genome, PLE accelerates host lysis, spreading the PLE while completely blocking phage production protecting V. cholerae at the population level. Here we identify a single PLE gene, lidI, sufficient to mediate accelerated lysis during ICP1 infection and demonstrate that LidI functions through disrupting lysis inhibition – an understudied outcome of phage infection when phages vastly outnumber their hosts. This work identifies ICP1-encoded holin and antiholin genes teaA and arrA respectively, that mediate this first example of lysis inhibition outside the T-even coliphages. Through lysis inhibition disruption, LidI is sufficient to limit the number of progeny phage produced from an infection. Consequently, this disruption bottlenecks ICP1 evolution as probed by recombination and CRISPR-Cas targeting assays. These studies link novel characterization of the classic phenomenon of lysis inhibition with a conserved protein in a dominant phage satellite, highlighting the importance of lysis timing during infection and parasitization, as well as providing insight into the populations, relationships, and evolution of bacteria, phages, and phage satellites in nature.ImportanceWith increasing awareness of microbiota impacting human health comes intensified examination of, not only bacteria and the bacteriophages that prey upon them, but also the mobile genetic elements (MGEs) that mediate interactions between them. Research is unveiling evolutionary strategies dependent on sensing the milieu: quorum sensing impacts phage infection, phage teamwork overcomes bacterial defenses, and abortive infections sacrifice single cells protecting populations. Yet, the first discovered environmental sensing by phages, known as lysis inhibition (LIN), has only been studied in the limited context of T-even coliphages. Here we characterize LIN in the etiological agent of the diarrheal disease cholera, Vibrio cholerae, infected by a phage ubiquitous in clinical samples. Further, we show that a specific MGE, the phage satellite PLE, collapses LIN with a conserved protein during its anti-phage program. The insights gleaned from this work add to our expanding understanding of microbial fitness in natural contexts beyond the canonical bacterial genome and into the realm of antagonistic evolution driven by phages and satellites.

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

DominantVibrio choleraephage exhibits lysis inhibition sensitive to disruption by a defensive phage satellite

Hays

Seed

2019

Preprint

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“…Studies in our laboratory showed that in the polylysogen, both phage-specific and host-specific DNA replication machineries are active and operate independently of each other; furthermore, the O and P functions are also needed for the maintenance of the full complement of 20-30 copies of prophage genomes [14]. The R and S gene products cause cell lysis [32], and thus, it is possible that their suboptimal expression from the multiple Ngenomes may cause the observed alterations of the polylysogen cell wall [33]. To complement our data on O and P genes [14], and to test the possible role of R and S, we tested the biochemical phenotypes of conversion in lysogens of the configuration 594(λN -cI -X -), where X is O, P, R, or S. The morphologies of the cells (Figure 11) show that loss of either R or S or both had no effect on the length of the filaments (i.e., they were essentially of the same length as the N -cIpolylysogen), whereas the loss of O or P led to shortening of the polylysogen filaments.…”

Section: Role Of Lambda Genes In Conversionmentioning

confidence: 99%

Altered Growth and Envelope Properties of Polylysogens Containing Bacteriophage Lambda N−cI− Prophages

Barik

Mandal

2020

IJMS

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The bacterial virus lambda (λ) is a temperate bacteriophage that can lysogenize host Escherichia coli (E. coli) cells. Lysogeny requires λ repressor, the cI gene product, which shuts off transcription of the phage genome. The λ N protein, in contrast, is a transcriptional antiterminator, required for expression of the terminator-distal genes, and thus, λ N mutants are growth-defective. When E. coli is infected with a λ double mutant that is defective in both N and cI (i.e., λN -cI -), at high multiplicities of 50 or more, it forms polylysogens that contain 20-30 copies of the λN -cIgenome integrated in the E. coli chromosome. Early studies revealed that the polylysogens underwent "conversion" to long filamentous cells that form tiny colonies on agar. Here, we report a large set of altered biochemical properties associated with this conversion, documenting an overall degeneration of the bacterial envelope. These properties reverted back to those of nonlysogenic E. coli as the metastable polylysogen spontaneously lost the λN -cIgenomes, suggesting that conversion is a direct result of the multiple copies of the prophage. Preliminary attempts to identify lambda genes that may be responsible for conversion ruled out several candidates, implicating a potentially novel lambda function that awaits further studies.

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“…Importantly, this has been linked to how phages can respond to changes in the environment of the host. That is, a shorter lifecycle provides fitness in a host-rich environment whereas a longer lifecycle is favored in a host-depleted setting (27,28). We would expect that the continued accumulation of the disruptin would abrogate the PMF, which would trigger the holin to initiate lysis prematurely.…”

Section: Disruptin Function In the Context Of Holin Controlmentioning

confidence: 99%

“…These assays were done in triplicate. (28), and the putative holin (29). Gene 28 encodes a 56 amino acid product.…”

Section: Minimal Inhibitory Concentration (Mic) and Minimal Bactericimentioning

confidence: 99%

Phage-encoded cationic antimicrobial peptide used for outer membrane disruption in lysis

Holt

Cahill

Ramsey

et al. 2019

Preprint

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Spanins are required for the last step in bacteriophage lysis: the disruption of the outer membrane. Bioinformatic analysis has shown that ~15% of phages lack a spanin gene, which suggests an alternate mechanism of outer membrane disruption. To address this, we selected virulent podophage ϕKT as a spaninless exemplar and tested ϕKT genes for outer membrane disruption during lysis. Hypothetical novel gene 28 causes outer membrane disruption when coexpressed with ϕKT lysis genes and complements the lysis defect of a λ spanin mutant. Gp28 is a 56 aa cationic peptide with predicted amphipathic helical structure and is associated with the particulate fraction after lysis. Urea and KCl washes did not release gp28 from the particulate, suggesting a strong hydrophobic interaction with the membrane. Super high-resolution microscopy supports a primarily outer membrane localization for the peptide. Additionally, holin function is not required for gp28-mediated lysis. Gp28 is similar in size, charge, predicted fold, and membrane association to the human cathelicidin antimicrobial peptide LL-37. In standard assays to measure bactericidal and inhibitory effects of antimicrobial peptides on bacterial cells, synthesized gp28 performed equivalently to LL-37. The studies presented here suggest that ϕKT gp28 disrupts bacterial outer membranes during lysis in a manner akin to antimicrobial peptides. SignificanceHere we provide evidence that ϕKT produces an antimicrobial peptide for outer membrane disruption during lysis. The disruptin is a new paradigm for phage lysis, and has no similarities to other known lysis genes. Many mechanisms have been proposed for the function of antimicrobial peptides, however there is not a consensus on the molecular basis of membrane disruption. Additionally, there is no established genetic selection system to support such studies. Therefore, the ϕKT disruptin may represent the first genetically tractable antimicrobial peptide.

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Phage Lysis: Multiple Genes for Multiple Barriers

Cited by 221 publications

References 110 publications

DominantVibrio choleraephage exhibits lysis inhibition sensitive to disruption by a defensive phage satellite

DominantVibrio choleraephage exhibits lysis inhibition sensitive to disruption by a defensive phage satellite

Altered Growth and Envelope Properties of Polylysogens Containing Bacteriophage Lambda N−cI− Prophages

Phage-encoded cationic antimicrobial peptide used for outer membrane disruption in lysis

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