1
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Nguyen TVP, Wu Y, Yao T, Trinh JT, Zeng L, Chemla YR, Golding I. Coinfecting phages impede each other's entry into the cell. Curr Biol 2024; 34:2841-2853.e18. [PMID: 38878771 PMCID: PMC11233250 DOI: 10.1016/j.cub.2024.05.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 02/15/2024] [Accepted: 05/16/2024] [Indexed: 06/25/2024]
Abstract
The developmental choice made by temperate phages, between cell death (lysis) and viral dormancy (lysogeny), is influenced by the relative abundance of viruses and hosts in the environment. The paradigm for this abundance-driven decision is phage lambda of E. coli, whose propensity to lysogenize increases with the number of viruses coinfecting the same bacterium. It is believed that lambda uses this number to infer whether phages or bacteria outnumber each other. However, this interpretation is premised on an accurate mapping between the extracellular phage-to-bacteria ratio and the intracellular multiplicity of infection (MOI). Here, we show this premise to be faulty. By simultaneously labeling phage capsids and genomes, we find that, while the number of phages landing on each cell reliably samples the population ratio, the number of phages entering the cell does not. Single-cell infections, performed in a microfluidic device and interpreted using a stochastic model, reveal that the probability and rate of phage entry decrease with the number of adsorbed phages. This decrease reflects an MOI-dependent perturbation to host physiology caused by phage attachment, as evidenced by compromised membrane integrity and loss of membrane potential. The dependence of entry dynamics on the surrounding medium results in a strong impact on the infection outcome, while the protracted entry of coinfecting phages increases the heterogeneity in infection outcome at a given MOI. Our findings in lambda, and similar results we obtained for phages T5 and P1, demonstrate the previously unappreciated role played by entry dynamics in determining the outcome of bacteriophage infection.
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Affiliation(s)
- Thu Vu Phuc Nguyen
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Yuchen Wu
- Center for Biophysics and Quantitative Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Tianyou Yao
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Jimmy T Trinh
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA; Center for Phage Technology, Texas A&M University, College Station, TX 77843, USA
| | - Lanying Zeng
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA; Center for Phage Technology, Texas A&M University, College Station, TX 77843, USA
| | - Yann R Chemla
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA; Center for Biophysics and Quantitative Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Ido Golding
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Department of Microbiology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
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2
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Fizari M, Keller N, Jardine PJ, Smith DE. Role of DNA-DNA sliding friction and nonequilibrium dynamics in viral genome ejection and packaging. Nucleic Acids Res 2023; 51:8060-8069. [PMID: 37449417 PMCID: PMC10450192 DOI: 10.1093/nar/gkad582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/17/2023] [Accepted: 06/27/2023] [Indexed: 07/18/2023] Open
Abstract
Many viruses eject their DNA via a nanochannel in the viral shell, driven by internal forces arising from the high-density genome packing. The speed of DNA exit is controlled by friction forces that limit the molecular mobility, but the nature of this friction is unknown. We introduce a method to probe the mobility of the tightly confined DNA by measuring DNA exit from phage phi29 capsids with optical tweezers. We measure extremely low initial exit velocity, a regime of exponentially increasing velocity, stochastic pausing that dominates the kinetics and large dynamic heterogeneity. Measurements with variable applied force provide evidence that the initial velocity is controlled by DNA-DNA sliding friction, consistent with a Frenkel-Kontorova model for nanoscale friction. We confirm several aspects of the ejection dynamics predicted by theoretical models. Features of the pausing suggest that it is connected to the phenomenon of 'clogging' in soft matter systems. Our results provide evidence that DNA-DNA friction and clogging control the DNA exit dynamics, but that this friction does not significantly affect DNA packaging.
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Affiliation(s)
- Mounir Fizari
- Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Nicholas Keller
- Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Paul J Jardine
- Department of Diagnostic and Biological Sciences and Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Douglas E Smith
- Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA
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3
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Bong S, Park CB, Cho SG, Bae J, Hapsari N, Jin X, Heo S, Lee JE, Hashiya K, Bando T, Sugiyama H, Jung KH, Sung B, Jo K. AT-specific DNA visualization revisits the directionality of bacteriophage λ DNA ejection. Nucleic Acids Res 2023; 51:5634-5646. [PMID: 37158237 PMCID: PMC10287942 DOI: 10.1093/nar/gkad340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 03/14/2023] [Accepted: 04/21/2023] [Indexed: 05/10/2023] Open
Abstract
In this study, we specifically visualized DNA molecules at their AT base pairs after in vitro phage ejection. Our AT-specific visualization revealed that either end of the DNA molecule could be ejected first with a nearly 50% probability. This observation challenges the generally accepted theory of Last In First Out (LIFO), which states that the end of the phage λ DNA that enters the capsid last during phage packaging is the first to be ejected, and that both ends of the DNA are unable to move within the extremely condensed phage capsid. To support our observations, we conducted computer simulations that revealed that both ends of the DNA molecule are randomized, resulting in the observed near 50% probability. Additionally, we found that the length of the ejected DNA by LIFO was consistently longer than that by First In First Out (FIFO) during in vitro phage ejection. Our simulations attributed this difference in length to the stiffness difference of the remaining DNA within the phage capsid. In conclusion, this study demonstrates that a DNA molecule within an extremely dense phage capsid exhibits a degree of mobility, allowing it to switch ends during ejection.
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Affiliation(s)
- Serang Bong
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Chung Bin Park
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Shin-Gyu Cho
- Department of Life Science, Sogang University, Seoul 04107, Korea
| | - Jaeyoung Bae
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Natalia Diyah Hapsari
- Department of Chemistry, Sogang University, Seoul 04107, Korea
- Chemistry Education Program, Department of Mathematics and Science Education, Sanata Dharma University, Yogyakarta 55282, Indonesia
| | - Xuelin Jin
- Department of Chemistry, Sogang University, Seoul 04107, Korea
- College of Agriculture, Yanbian University, Yanji133000, China
| | - Sujung Heo
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Ji-eun Lee
- Department of Life Science, Sogang University, Seoul 04107, Korea
| | - Kaori Hashiya
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-Ku, Kyoto606-8502, Japan
| | - Toshikazu Bando
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-Ku, Kyoto606-8502, Japan
| | - Hiroshi Sugiyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-Ku, Kyoto606-8502, Japan
| | - Kwang-Hwan Jung
- Department of Life Science, Sogang University, Seoul 04107, Korea
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Kyubong Jo
- Department of Chemistry, Sogang University, Seoul 04107, Korea
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4
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Nguyen TVP, Wu Y, Yao T, Trinh JT, Zeng L, Chemla YR, Golding I. CO-INFECTING PHAGES IMPEDE EACH OTHER'S ENTRY INTO THE CELL. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.05.543643. [PMID: 37333217 PMCID: PMC10274716 DOI: 10.1101/2023.06.05.543643] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Bacteriophage lambda tunes its propensity to lysogenize based on the number of viral genome copies inside the infected cell. Viral self-counting is believed to serve as a way of inferring the abundance of available hosts in the environment. This interpretation is premised on an accurate mapping between the extracellular phage-to-bacteria ratio and the intracellular multiplicity of infection (MOI). However, here we show this premise to be untrue. By simultaneously labeling phage capsids and genomes, we find that, while the number of phages landing on each cell reliably samples the population ratio, the number of phages entering the cell does not. Single-cell infections, followed in a microfluidic device and interpreted using a stochastic model, reveal that the probability and rate of individual phage entries decrease with MOI. This decrease reflects an MOI-dependent perturbation to host physiology caused by phage landing, evidenced by compromised membrane integrity and loss of membrane potential. The dependence of phage entry dynamics on the surrounding medium is found to result in a strong impact of environmental conditions on the infection outcome, while the protracted entry of co-infecting phages increases the cell-to-cell variability in infection outcome at a given MOI. Our findings demonstrate the previously unappreciated role played by entry dynamics in determining the outcome of bacteriophage infection.
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Affiliation(s)
- Thu Vu Phuc Nguyen
- Department of Physics, University of Illinois Urbana–Champaign, Urbana, IL 61801, USA
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, TX 77030, USA
| | - Yuchen Wu
- Center for Biophysics and Quantitative Biology, University of Illinois Urbana–Champaign, Urbana, IL 61801, USA
| | - Tianyou Yao
- Department of Physics, University of Illinois Urbana–Champaign, Urbana, IL 61801, USA
| | - Jimmy T. Trinh
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
- Center for Phage Technology, Texas A&M University, College Station, TX 77843, USA
| | - Lanying Zeng
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
- Center for Phage Technology, Texas A&M University, College Station, TX 77843, USA
| | - Yann R. Chemla
- Department of Physics, University of Illinois Urbana–Champaign, Urbana, IL 61801, USA
- Center for Biophysics and Quantitative Biology, University of Illinois Urbana–Champaign, Urbana, IL 61801, USA
| | - Ido Golding
- Department of Physics, University of Illinois Urbana–Champaign, Urbana, IL 61801, USA
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, TX 77030, USA
- Department of Microbiology, University of Illinois Urbana–Champaign, Urbana, IL 61801, USA
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5
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Fizari M, Keller N, Jardine PJ, Smith DE. Role of DNA-DNA sliding friction and non-equilibrium dynamics in viral genome ejection and packaging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.03.535472. [PMID: 37066220 PMCID: PMC10104077 DOI: 10.1101/2023.04.03.535472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Many viruses eject their DNA via a nanochannel in the viral shell, driven by internal forces arising from the high-density genome packing. The speed of DNA exit is controlled by friction forces that limit the molecular mobility, but the nature of this friction is unknown. We introduce a method to probe the mobility of the tightly confined DNA by measuring DNA exit from phage phi29 capsids with optical tweezers. We measure extremely low initial exit velocity, a regime of exponentially increasing velocity, stochastic pausing that dominates the kinetics, and large dynamic heterogeneity. Measurements with variable applied force provide evidence that the initial velocity is controlled by DNA-DNA sliding friction, consistent with a Frenkel-Kontorova model for nanoscale friction. We confirm several aspects of the ejection dynamics predicted by theoretical models. Features of the pausing suggest it is connected to the phenomenon of "clogging" in soft-matter systems. Our results provide evidence that DNA-DNA friction and clogging control the DNA exit dynamics, but that this friction does not significantly affect DNA packaging.
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6
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Dulberger CL, Guerrero-Bustamante CA, Owen SV, Wilson S, Wuo MG, Garlena RA, Serpa LA, Russell DA, Zhu J, Braunecker BJ, Squyres GR, Baym M, Kiessling LL, Garner EC, Rubin EJ, Hatfull GF. Mycobacterial nucleoid-associated protein Lsr2 is required for productive mycobacteriophage infection. Nat Microbiol 2023; 8:695-710. [PMID: 36823286 PMCID: PMC10066036 DOI: 10.1038/s41564-023-01333-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 01/23/2023] [Indexed: 02/25/2023]
Abstract
Mycobacteriophages are a diverse group of viruses infecting Mycobacterium with substantial therapeutic potential. However, as this potential becomes realized, the molecular details of phage infection and mechanisms of resistance remain ill-defined. Here we use live-cell fluorescence microscopy to visualize the spatiotemporal dynamics of mycobacteriophage infection in single cells and populations, showing that infection is dependent on the host nucleoid-associated Lsr2 protein. Mycobacteriophages preferentially adsorb at Mycobacterium smegmatis sites of new cell wall synthesis and following DNA injection, Lsr2 reorganizes away from host replication foci to establish zones of phage DNA replication (ZOPR). Cells lacking Lsr2 proceed through to cell lysis when infected but fail to generate consecutive phage bursts that trigger epidemic spread of phage particles to neighbouring cells. Many mycobacteriophages code for their own Lsr2-related proteins, and although their roles are unknown, they do not rescue the loss of host Lsr2.
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Affiliation(s)
- Charles L Dulberger
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, USA.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | | | - Siân V Owen
- Department of Biomedical Informatics and Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Sean Wilson
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Michael G Wuo
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Rebecca A Garlena
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Lexi A Serpa
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Daniel A Russell
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Junhao Zhu
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, USA
| | - Ben J Braunecker
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, USA
| | - Georgia R Squyres
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Michael Baym
- Department of Biomedical Informatics and Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Laura L Kiessling
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Ethan C Garner
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Eric J Rubin
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, USA.
| | - Graham F Hatfull
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA.
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7
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Tail proteins of phage SU10 reorganize into the nozzle for genome delivery. Nat Commun 2022; 13:5622. [PMID: 36153309 PMCID: PMC9509320 DOI: 10.1038/s41467-022-33305-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 09/12/2022] [Indexed: 12/23/2022] Open
Abstract
Escherichia coli phage SU10 belongs to the genus Kuravirus from the class Caudoviricetes of phages with short non-contractile tails. In contrast to other short-tailed phages, the tails of Kuraviruses elongate upon cell attachment. Here we show that the virion of SU10 has a prolate head, containing genome and ejection proteins, and a tail, which is formed of portal, adaptor, nozzle, and tail needle proteins and decorated with long and short fibers. The binding of the long tail fibers to the receptors in the outer bacterial membrane induces the straightening of nozzle proteins and rotation of short tail fibers. After the re-arrangement, the nozzle proteins and short tail fibers alternate to form a nozzle that extends the tail by 28 nm. Subsequently, the tail needle detaches from the nozzle proteins and five types of ejection proteins are released from the SU10 head. The nozzle with the putative extension formed by the ejection proteins enables the delivery of the SU10 genome into the bacterial cytoplasm. It is likely that this mechanism of genome delivery, involving the formation of the tail nozzle, is employed by all Kuraviruses. E. coli phage SU10 has a short non-contractile tail. Here, the authors show that after cell binding, nozzle proteins and tail fibers of SU10 change conformation to form a nozzle that enables the delivery of the phage DNA into the bacterial cytoplasm.
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8
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Imaging the Infection Cycle of T7 at the Single Virion Level. Int J Mol Sci 2022; 23:ijms231911252. [PMID: 36232552 PMCID: PMC9569847 DOI: 10.3390/ijms231911252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 09/17/2022] [Accepted: 09/21/2022] [Indexed: 11/17/2022] Open
Abstract
T7 phages are E. coli-infecting viruses that find and invade their target with high specificity and efficiency. The exact molecular mechanisms of the T7 infection cycle are yet unclear. As the infection involves mechanical events, single-particle methods are to be employed to alleviate the problems of ensemble averaging. Here we used TIRF microscopy to uncover the spatial dynamics of the target recognition and binding by individual T7 phage particles. In the initial phase, T7 virions bound reversibly to the bacterial membrane via two-dimensional diffusive exploration. Stable bacteriophage anchoring was achieved by tail-fiber complex to receptor binding which could be observed in detail by atomic force microscopy (AFM) under aqueous buffer conditions. The six anchored fibers of a given T7 phage-displayed isotropic spatial orientation. The viral infection led to the onset of an irreversible structural program in the host which occurred in three distinct steps. First, bacterial cell surface roughness, as monitored by AFM, increased progressively. Second, membrane blebs formed on the minute time scale (average ~5 min) as observed by phase-contrast microscopy. Finally, the host cell was lysed in a violent and explosive process that was followed by the quick release and dispersion of the phage progeny. DNA ejection from T7 could be evoked in vitro by photothermal excitation, which revealed that genome release is mechanically controlled to prevent premature delivery of host-lysis genes. The single-particle approach employed here thus provided an unprecedented insight into the details of the complete viral cycle.
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9
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Jang HB, Chittick L, Li YF, Zablocki O, Sanderson CM, Carrillo A, van den Engh G, Sullivan MB. Viral tag and grow: a scalable approach to capture and characterize infectious virus-host pairs. ISME COMMUNICATIONS 2022; 2:12. [PMID: 37938680 PMCID: PMC9723727 DOI: 10.1038/s43705-022-00093-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 01/06/2022] [Accepted: 01/13/2022] [Indexed: 04/27/2023]
Abstract
Viral metagenomics (viromics) has reshaped our understanding of DNA viral diversity, ecology, and evolution across Earth's ecosystems. However, viromics now needs approaches to link newly discovered viruses to their host cells and characterize them at scale. This study adapts one such method, sequencing-enabled viral tagging (VT), to establish "Viral Tag and Grow" (VT + Grow) to rapidly capture and characterize viruses that infect a cultivated target bacterium, Pseudoalteromonas. First, baseline cytometric and microscopy data improved understanding of how infection conditions and host physiology impact populations in VT flow cytograms. Next, we extensively evaluated "and grow" capability to assess where VT signals reflect adsorption alone or wholly successful infections that lead to lysis. Third, we applied VT + Grow to a clonal virus stock, which, coupled to traditional plaque assays, revealed significant variability in burst size-findings that hint at a viral "individuality" parallel to the microbial phenotypic heterogeneity literature. Finally, we established a live protocol for public comment and improvement via protocols.io to maximally empower the research community. Together these efforts provide a robust foundation for VT researchers, and establish VT + Grow as a promising scalable technology to capture and characterize viruses from mixed community source samples that infect cultivable bacteria.
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Affiliation(s)
- Ho Bin Jang
- Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | - Lauren Chittick
- Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | - Yueh-Fen Li
- Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | - Olivier Zablocki
- Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | | | - Alfonso Carrillo
- Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | | | - Matthew B Sullivan
- Department of Microbiology, The Ohio State University, Columbus, OH, USA.
- Department of Civil, Environmental and Geodetic Engineering, The Ohio State University, Columbus, OH, USA.
- Center of Microbiome Science, The Ohio State University, Columbus, OH, USA.
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10
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Owen SV, Wenner N, Dulberger CL, Rodwell EV, Bowers-Barnard A, Quinones-Olvera N, Rigden DJ, Rubin EJ, Garner EC, Baym M, Hinton JCD. Prophages encode phage-defense systems with cognate self-immunity. Cell Host Microbe 2021; 29:1620-1633.e8. [PMID: 34597593 PMCID: PMC8585504 DOI: 10.1016/j.chom.2021.09.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 02/23/2021] [Accepted: 09/03/2021] [Indexed: 12/18/2022]
Abstract
Temperate phages are pervasive in bacterial genomes, existing as vertically inherited islands termed prophages. Prophages are vulnerable to predation of their host bacterium by exogenous phages. Here, we identify BstA, a family of prophage-encoded phage-defense proteins in diverse Gram-negative bacteria. BstA localizes to sites of exogenous phage DNA replication and mediates abortive infection, suppressing the competing phage epidemic. During lytic replication, the BstA-encoding prophage is not itself inhibited by BstA due to self-immunity conferred by the anti-BstA (aba) element, a short stretch of DNA within the bstA locus. Inhibition of phage replication by distinct BstA proteins from Salmonella, Klebsiella, and Escherichia prophages is generally interchangeable, but each possesses a cognate aba element. The specificity of the aba element ensures that immunity is exclusive to the replicating prophage, preventing exploitation by variant BstA-encoding phages. The BstA protein allows prophages to defend host cells against exogenous phage attack without sacrificing the ability to replicate lytically. BstA is an abortive infection protein found in prophages of Gram-negative bacteria aba, a short DNA sequence within the bstA locus, acts as a self-immunity element aba gives BstA-encoding prophages immunity to BstA-driven abortive infection Variant BstA proteins have distinct and cognate aba elements
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Affiliation(s)
- Siân V Owen
- Department of Biomedical Informatics and Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA, USA.
| | - Nicolas Wenner
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK; Biozentrum, University of Basel, Basel, Switzerland
| | - Charles L Dulberger
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, USA; Department of Molecular and Cellular Biology, Harvard University, Boston, MA, USA
| | - Ella V Rodwell
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Arthur Bowers-Barnard
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Natalia Quinones-Olvera
- Department of Biomedical Informatics and Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Daniel J Rigden
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, UK
| | - Eric J Rubin
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Ethan C Garner
- Department of Molecular and Cellular Biology, Harvard University, Boston, MA, USA
| | - Michael Baym
- Department of Biomedical Informatics and Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA, USA.
| | - Jay C D Hinton
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK.
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11
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Park CB, Sung BJ. Effects of Packaging History on the Ejection of a Polymer Chain from a Small Confinement. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00857] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Chung Bin Park
- Department of Chemistry and Research Institute for Basic Science, Sogang University, Seoul 04107, Republic of Korea
| | - Bong June Sung
- Department of Chemistry and Research Institute for Basic Science, Sogang University, Seoul 04107, Republic of Korea
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12
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Hantke K. Compilation of Escherichia coli K-12 outer membrane phage receptors - their function and some historical remarks. FEMS Microbiol Lett 2021; 367:5721240. [PMID: 32009155 DOI: 10.1093/femsle/fnaa013] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 01/31/2020] [Indexed: 02/07/2023] Open
Abstract
Many Escherichia coli phages have been sequenced, but in most cases their sequences alone do not suffice to predict their host specificity. Analysis of phage resistant E. coli K-12 mutants have uncovered a certain set of outer membrane proteins and polysaccharides as receptors. In this review, a compilation of E. coli K12 phage receptors is provided and their functional characterization, often driven by studies on phage resistant mutants, is discussed in the historical context. While great progress has been made in this field thus far, several proteins in the outer membrane still await characterization as phage receptors.
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Affiliation(s)
- Klaus Hantke
- IMIT, Interfakultäres Institut für Mikrobiologie und Infektionsmedizin University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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13
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Cambré A, Aertsen A. Bacterial Vivisection: How Fluorescence-Based Imaging Techniques Shed a Light on the Inner Workings of Bacteria. Microbiol Mol Biol Rev 2020; 84:e00008-20. [PMID: 33115939 PMCID: PMC7599038 DOI: 10.1128/mmbr.00008-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The rise in fluorescence-based imaging techniques over the past 3 decades has improved the ability of researchers to scrutinize live cell biology at increased spatial and temporal resolution. In microbiology, these real-time vivisections structurally changed the view on the bacterial cell away from the "watery bag of enzymes" paradigm toward the perspective that these organisms are as complex as their eukaryotic counterparts. Capitalizing on the enormous potential of (time-lapse) fluorescence microscopy and the ever-extending pallet of corresponding probes, initial breakthroughs were made in unraveling the localization of proteins and monitoring real-time gene expression. However, later it became clear that the potential of this technique extends much further, paving the way for a focus-shift from observing single events within bacterial cells or populations to obtaining a more global picture at the intra- and intercellular level. In this review, we outline the current state of the art in fluorescence-based vivisection of bacteria and provide an overview of important case studies to exemplify how to use or combine different strategies to gain detailed information on the cell's physiology. The manuscript therefore consists of two separate (but interconnected) parts that can be read and consulted individually. The first part focuses on the fluorescent probe pallet and provides a perspective on modern methodologies for microscopy using these tools. The second section of the review takes the reader on a tour through the bacterial cell from cytoplasm to outer shell, describing strategies and methods to highlight architectural features and overall dynamics within cells.
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Affiliation(s)
- Alexander Cambré
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Leuven, Belgium
| | - Abram Aertsen
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Leuven, Belgium
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14
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Kiss B, Mudra D, Török G, Mártonfalvi Z, Csík G, Herényi L, Kellermayer M. Single-particle virology. Biophys Rev 2020; 12:1141-1154. [PMID: 32880826 PMCID: PMC7471434 DOI: 10.1007/s12551-020-00747-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 08/18/2020] [Indexed: 01/02/2023] Open
Abstract
The development of advanced experimental methodologies, such as optical tweezers, scanning-probe and super-resolved optical microscopies, has led to the evolution of single-molecule biophysics, a field of science that allows direct access to the mechanistic detail of biomolecular structure and function. The extension of single-molecule methods to the investigation of particles such as viruses permits unprecedented insights into the behavior of supramolecular assemblies. Here we address the scope of viral exploration at the level of individual particles. In an era of increased awareness towards virology, single-particle approaches are expected to facilitate the in-depth understanding, and hence combating, of viral diseases.
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Affiliation(s)
- Bálint Kiss
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Dorottya Mudra
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - György Török
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Zsolt Mártonfalvi
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Gabriella Csík
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Levente Herényi
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Miklós Kellermayer
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary.
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15
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Mutagenic Analysis of a DNA Translocating Tube's Interior Surface. Viruses 2020; 12:v12060670. [PMID: 32580341 PMCID: PMC7354561 DOI: 10.3390/v12060670] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 01/06/2023] Open
Abstract
Bacteriophage ϕX174 uses a decamer of DNA piloting proteins to penetrate its host. These proteins oligomerize into a cell wall-spanning tube, wide enough for genome passage. While the inner surface of the tube is primarily lined with inward-facing amino acid side chains containing amide and guanidinium groups, there is a 28 Å-long section near the tube’s C-terminus that does not exhibit this motif. The majority of the inward-facing residues in this region are conserved across the three ϕX174-like clades, suggesting that they play an important role during genome delivery. To test this hypothesis, and explore the general function of the tube’s inner surface, non-glutamine residues within this region were mutated to glutamine, while existing glutamine residues were changed to serine. Four of the resulting mutants had temperature-dependent phenotypes. Virion assembly, host attachment, and virion eclipse, defined as the cell’s ability to inactivate the virus, were not affected. Genome delivery, however, was inhibited. The results support a model in which a balance of forces governs genome delivery: potential energy provided by the densely packaged viral genome and/or an osmotic gradient move the genome into the cell, while the tube’s inward facing glutamine residues exert a frictional force, or drag, that controls genome release.
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16
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Brandariz-Nuñez A, Liu T, Du T, Evilevitch A. Pressure-driven release of viral genome into a host nucleus is a mechanism leading to herpes infection. eLife 2019; 8:47212. [PMID: 31393262 PMCID: PMC6711703 DOI: 10.7554/elife.47212] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 08/04/2019] [Indexed: 12/31/2022] Open
Abstract
Many viruses previously have been shown to have pressurized genomes inside their viral protein shell, termed the capsid. This pressure results from the tight confinement of negatively charged viral nucleic acids inside the capsid. However, the relevance of capsid pressure to viral infection has not been demonstrated. In this work, we show that the internal DNA pressure of tens of atmospheres inside a herpesvirus capsid powers ejection of the viral genome into a host cell nucleus. To our knowledge, this provides the first demonstration of a pressure-dependent mechanism of viral genome penetration into a host nucleus, leading to infection of eukaryotic cells.
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Affiliation(s)
- Alberto Brandariz-Nuñez
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, United States
| | - Ting Liu
- Department of Physics, Carnegie Mellon University, Pittsburgh, United States
| | - Te Du
- The Marjorie B. Kovler Viral Oncology Laboratories, The University of Chicago, Chicago, United States
| | - Alex Evilevitch
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, United States.,Department of Experimental Medical Sciences, Lund University, Lund, Sweden
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17
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Park CB, Kwon S, Sung BJ. The effects of a knot and its conformational relaxation on the ejection of a single polymer chain from confinement. J Chem Phys 2019. [DOI: 10.1063/1.5110428] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chung Bin Park
- Department of Chemistry, Sogang University, Seoul 04107, South Korea
| | - Seulki Kwon
- Department of Chemistry, Sogang University, Seoul 04107, South Korea
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, South Korea
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18
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Broeker NK, Roske Y, Valleriani A, Stephan MS, Andres D, Koetz J, Heinemann U, Barbirz S. Time-resolved DNA release from an O-antigen-specific Salmonella bacteriophage with a contractile tail. J Biol Chem 2019; 294:11751-11761. [PMID: 31189652 PMCID: PMC6682738 DOI: 10.1074/jbc.ra119.008133] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 06/11/2019] [Indexed: 12/20/2022] Open
Abstract
Myoviruses, bacteriophages with T4-like architecture, must contract their tails prior to DNA release. However, quantitative kinetic data on myovirus particle opening are lacking, although they are promising tools in bacteriophage-based antimicrobial strategies directed against Gram-negative hosts. For the first time, we show time-resolved DNA ejection from a bacteriophage with a contractile tail, the multi-O-antigen-specific Salmonella myovirus Det7. DNA release from Det7 was triggered by lipopolysaccharide (LPS) O-antigen receptors and notably slower than in noncontractile-tailed siphoviruses. Det7 showed two individual kinetic steps for tail contraction and particle opening. Our in vitro studies showed that highly specialized tailspike proteins (TSPs) are necessary to attach the particle to LPS. A P22-like TSP confers specificity for the Salmonella Typhimurium O-antigen. Moreover, crystal structure analysis at 1.63 Å resolution confirmed that Det7 recognized the Salmonella Anatum O-antigen via an ϵ15-like TSP, DettilonTSP. DNA ejection triggered by LPS from either host showed similar velocities, so particle opening is thus a process independent of O-antigen composition and the recognizing TSP. In Det7, at permissive temperatures TSPs mediate O-antigen cleavage and couple cell surface binding with DNA ejection, but no irreversible adsorption occurred at low temperatures. This finding was in contrast to short-tailed Salmonella podoviruses, illustrating that tailed phages use common particle-opening mechanisms but have specialized into different infection niches.
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Affiliation(s)
- Nina K Broeker
- Department of Physikalische Biochemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
| | - Yvette Roske
- Max-Delbrück-Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Angelo Valleriani
- Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Mareike S Stephan
- Department of Physikalische Biochemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
| | - Dorothee Andres
- Department of Physikalische Biochemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
| | - Joachim Koetz
- Kolloidchemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
| | - Udo Heinemann
- Max-Delbrück-Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
- Institut für Chemie und Biochemie, Freie Universität, Takustrasse 6, 14195 Berlin, Germany
| | - Stefanie Barbirz
- Department of Physikalische Biochemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
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19
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Guan J, Ibarra D, Zeng L. The role of side tail fibers during the infection cycle of phage lambda. Virology 2018; 527:57-63. [PMID: 30463036 DOI: 10.1016/j.virol.2018.11.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 11/07/2018] [Accepted: 11/08/2018] [Indexed: 11/17/2022]
Abstract
Bacteriophage λ has served as an important model for molecular biology and different cellular processes over the past few decades. In 1992, the phage strain used in most laboratories around the world, thought of as λ wild type, was discovered to carry a mutation in the stf gene which encodes four side tail fibers. Up to now, the role of the side tail fibers during the infection cycle, especially at the single-cell level, remains largely unknown. Here we utilized fluorescent reporter systems to characterize the effect of the side tail fibers on phage infection. We found that the side tail fibers interfere with phage DNA ejection process, most likely through the binding with their receptors, OmpC, leading to a more frequent failed infection. However, the side tail fibers do not seem to affect the lysis-lysogeny decision-making or lysis time.
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Affiliation(s)
- Jingwen Guan
- Molecular and Environmental Plant Science, Texas A&M University, College Station, TX 77843, USA; Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA; Center for Phage Technology, Texas A&M University, College Station, TX 77843, USA
| | - David Ibarra
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
| | - Lanying Zeng
- Molecular and Environmental Plant Science, Texas A&M University, College Station, TX 77843, USA; Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA; Center for Phage Technology, Texas A&M University, College Station, TX 77843, USA.
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20
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Shao Q, Trinh JT, Zeng L. High-resolution studies of lysis-lysogeny decision-making in bacteriophage lambda. J Biol Chem 2018; 294:3343-3349. [PMID: 30242122 DOI: 10.1074/jbc.tm118.003209] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Cellular decision-making guides complex development such as cell differentiation and disease progression. Much of our knowledge about decision-making is derived from simple models, such as bacteriophage lambda infection, in which lambda chooses between the vegetative lytic fate and the dormant lysogenic fate. This paradigmatic system is broadly understood but lacking mechanistic details, partly due to limited resolution of past studies. Here, we discuss how modern technologies have enabled high-resolution examination of lambda decision-making to provide new insights and exciting possibilities in studying this classical system. The advent of techniques for labeling specific DNA, RNA, and proteins in cells allows for molecular-level characterization of events in lambda development. These capabilities yield both new answers and new questions regarding how the isolated lambda genetic circuit acts, what biological events transpire among phages in their natural context, and how the synergy of simple phage macromolecules brings about complex behaviors.
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Affiliation(s)
- Qiuyan Shao
- From the Department of Biochemistry and Biophysics and.,the Center for Phage Technology, Texas A&M University, College Station, Texas 77843
| | - Jimmy T Trinh
- From the Department of Biochemistry and Biophysics and.,the Center for Phage Technology, Texas A&M University, College Station, Texas 77843
| | - Lanying Zeng
- From the Department of Biochemistry and Biophysics and .,the Center for Phage Technology, Texas A&M University, College Station, Texas 77843
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21
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Evilevitch A. The mobility of packaged phage genome controls ejection dynamics. eLife 2018; 7:37345. [PMID: 30178745 PMCID: PMC6122950 DOI: 10.7554/elife.37345] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Accepted: 07/29/2018] [Indexed: 12/31/2022] Open
Abstract
The cell decision between lytic and lysogenic infection is strongly influenced by dynamics of DNA injection into a cell from a phage population, as phages compete for limited resources and progeny. However, what controls the timing of viral DNA ejection events was not understood. This in vitro study reveals that DNA ejection dynamics for phages can be synchronized (occurring within seconds) or desynchronized (displaying minutes-long delays in initiation) based on mobility of encapsidated DNA, which in turn is regulated by environmental factors, such as temperature and extra-cellular ionic conditions. This mechano-regulation of ejection dynamics is suggested to influence viral replication where the cell’s decision between lytic and latent infection is associated with synchronized or desynchronized delayed ejection events from phage population adsorbed to a cell. Our findings are of significant importance for understanding regulatory mechanisms of latency in phage and Herpesviruses, where encapsidated DNA undergoes a similar mechanical transition. Viruses are tiny ‘parasites’ that smuggle their genetic material inside a cell and then hijack its resources for their own benefit. A viral infection can either be lytic or latent. In a lytic cycle, viruses make their host produce many copies of themselves, ultimately killing the cell. In contrast, during a latent infection, the viruses go ‘dormant’: for instance, some of them can insert their genetic material into the DNA of their host, which then gets passed on as the cell divides. Certain viruses are capable of both lytic and latent infections. One example is the lambda phage, which targets Escherichia coli bacteria. In the first stage of infection, the genetic material ‘shoots out’ of the virus and gets injected inside the bacterium. The dynamics of the ejection process determine the type of infection that will follow. If multiple phages release their genomes quickly and within seconds of each other into the same cell, the bacterium tends to incorporate the viral DNA into its own genome, leading to a latent cycle. If the infections take place more slowly and not all at the same time, the cell is more likely to go through a lytic phase. However, the mechanism behind the different injection behaviors is still unknown; in particular, it is unclear which factors control the specificities of the ejection process in the first place. Here, Alex Evilevitch demonstrates that the mechanical state of the phage DNA just before ejection dictates how the genetic material will then be injected in the bacteria. The experiments measured the stiffness of the DNA and the amount of heat given off during infection. Like fluid toothpaste, if the DNA is more liquid and flexible, it gets ejected quickly and simultaneously from several phages. Then, the genetic information of these viruses can be incorporated in the genome of the bacteria. On the other hand, if the DNA is more solid, it is likely to ‘stick’ and take time before it can be squeezed out: the injections become unsynchronised, which leads to a lytic phase. Evilevitch then shows that the environment can influence the properties of the phages’ genome. A little more heat, or certain chemicals, can make the DNA more fluid inside the viruses, and change the way it can be injected inside the bacteria. Many viruses that cause diseases in humans – from cold sores to glandular fever – can switch between the lytic and latent cycles. For the first time, these results show that the mechanical properties of the DNA inside a virus influence the ‘decision’ between the two types of infection. This knowledge could help us prevent infections from becoming lytic and ultimately allow us to control the spread of disease.
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Affiliation(s)
- Alex Evilevitch
- Department of Pathobiology, Division of Microbiology and Immunology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Champaign, United States.,Department of Experimental Medical Sciences, Virus Biophysics Group, Lund University, Lund, Sweden
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22
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Trinh JT, Alkahtani MH, Rampersaud I, Rampersaud A, Scully M, Young RF, Hemmer P, Zeng L. Fluorescent nanodiamond-bacteriophage conjugates maintain host specificity. Biotechnol Bioeng 2018; 115:1427-1436. [PMID: 29460442 PMCID: PMC5912989 DOI: 10.1002/bit.26573] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 01/29/2018] [Accepted: 02/13/2018] [Indexed: 12/15/2022]
Abstract
Rapid identification of specific bacterial strains within clinical, environmental, and food samples can facilitate the prevention and treatment of disease. Fluorescent nanodiamonds (FNDs) are being developed as biomarkers in biology and medicine, due to their excellent imaging properties, ability to accept surface modifications, and lack of toxicity. Bacteriophages, the viruses of bacteria, can have exquisite specificity for certain hosts. We propose to exploit the properties of FNDs and phages to develop phages conjugated with FNDs as long-lived fluorescent diagnostic reagents. In this study, we develop a simple procedure to create such fluorescent probes by functionalizing the FNDs and phages with streptavidin and biotin, respectively. We find that the FND-phage conjugates retain the favorable characteristics of the individual components and can discern their proper host within a mixture. This technology may be further explored using different phage/bacteria systems, different FND color centers and alternate chemical labeling schemes for additional means of bacterial identification and new single-cell/virus studies.
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Affiliation(s)
- Jimmy T. Trinh
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, 77843, USA
- Center for Phage Technology, Texas A&M University, College Station, Texas, 77843, USA
| | - Masfer H. Alkahtani
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, 77843, USA
- Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA
- The National Center for Applied Physics, KACST, P.O. Box 6086, Riyadh 11442, Saudi Arabia
| | | | | | - Marlan Scully
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, 77843, USA
- Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA
- Department of Physics, Baylor University, Waco, Texas, 76706, USA
| | - Ryland F. Young
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, 77843, USA
- Center for Phage Technology, Texas A&M University, College Station, Texas, 77843, USA
| | - Philip Hemmer
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, 77843, USA
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, 77843, USA
| | - Lanying Zeng
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, 77843, USA
- Center for Phage Technology, Texas A&M University, College Station, Texas, 77843, USA
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23
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Golding I. Infection by bacteriophage lambda: an evolving paradigm for cellular individuality. Curr Opin Microbiol 2018; 43:9-13. [PMID: 29107897 PMCID: PMC5934347 DOI: 10.1016/j.mib.2017.09.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 09/14/2017] [Accepted: 09/25/2017] [Indexed: 12/19/2022]
Abstract
Since the earliest days of molecular biology, bacteriophage lambda has served to illuminate cellular function. Among its many roles, lambda infection is a paradigm for phenotypic heterogeneity among genetically identical cells. Early studies attributed this cellular individuality to random biochemical fluctuations, or 'noise'. More recently, however, attention has turned to the role played by deterministic hidden variables in driving single-cell behavior. Here, I briefly describe how studies in lambda are driving the shift in our understanding of cellular heterogeneity, allowing us to better appreciate the precision at which cells function.
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Affiliation(s)
- Ido Golding
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Center for Theoretical Biological Physics, Rice University, Houston, TX 77005, USA.
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24
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Almeida GM, Leppänen M, Maasilta IJ, Sundberg LR. Bacteriophage imaging: past, present and future. Res Microbiol 2018; 169:488-494. [PMID: 29852217 DOI: 10.1016/j.resmic.2018.05.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 05/16/2018] [Accepted: 05/22/2018] [Indexed: 01/21/2023]
Abstract
The visualization of viral particles only became possible after the advent of the electron microscope. The first bacteriophage images were published in 1940 and were soon followed by many other publications that helped to elucidate the structure of the particles and their interaction with the bacterial hosts. As sample preparation improved and new technologies were developed, phage imaging became important approach to morphologically classify these viruses and helped to understand its importance in the biosphere. In this review we discuss the main milestones in phage imaging, how it affected our knowledge on these viruses and recent developments in the field.
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Affiliation(s)
- Gabriel Mf Almeida
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, Nanoscience Center, University of Jyväskylä, Survontie 9C, FI-40014, Jyväskylä, Finland.
| | - Miika Leppänen
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, Nanoscience Center, University of Jyväskylä, Survontie 9C, FI-40014, Jyväskylä, Finland; Department of Physics, Nanoscience Center, University of Jyväskylä, Survontie 9C, FI-40014, Jyväskylä, Finland.
| | - Ilari J Maasilta
- Department of Physics, Nanoscience Center, University of Jyväskylä, Survontie 9C, FI-40014, Jyväskylä, Finland.
| | - Lotta-Riina Sundberg
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, Nanoscience Center, University of Jyväskylä, Survontie 9C, FI-40014, Jyväskylä, Finland.
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25
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Kellermayer MSZ, Vörös Z, Csík G, Herényi L. Forced phage uncorking: viral DNA ejection triggered by a mechanically sensitive switch. NANOSCALE 2018; 10:1898-1904. [PMID: 29318247 DOI: 10.1039/c7nr05897g] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The foremost event of bacteriophage infection is the ejection of genomic material into the host bacterium after virus binding to surface receptor sites. How ejection is triggered is yet unknown. Here we show, in single mature T7 phage particles, that tapping the capsid wall with an oscillating atomic-force-microscope cantilever triggers rapid DNA ejection via the tail complex. The triggering rate increases exponentially as a function of force, following transition-state theory, across an activation barrier of 23 kcal mol-1 at 1.2 nm along the reaction coordinate. The conformation of the ejected DNA molecule revealed that it had been exposed to a propulsive force. This force, arising from intra-capsid pressure, assists in initiating the ejection process and the transfer of DNA across spatial dimensions beyond that of the virion. Chemical immobilization of the tail fibers also resulted in enhanced DNA ejection, suggesting that the triggering process might involve a conformational switch that can be mechanically activated either by external forces or via the tail-fiber complex.
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Affiliation(s)
- Miklós S Z Kellermayer
- Department of Biophysics and Radiation Biology, Semmelweis University, Tűzoltó u. 37-47, Budapest H-1094, Hungary.
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26
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Late-Arriving Signals Contribute Less to Cell-Fate Decisions. Biophys J 2017; 113:2110-2120. [PMID: 29117533 DOI: 10.1016/j.bpj.2017.09.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 08/14/2017] [Accepted: 09/05/2017] [Indexed: 11/24/2022] Open
Abstract
Gene regulatory networks are largely responsible for cellular decision-making. These networks sense diverse external signals and respond by adjusting gene expression, enabling cells to reach environment-dependent decisions crucial for their survival or reproduction. However, information-carrying signals may arrive at variable times. Besides the intrinsic strength of these signals, their arrival time (timing) may also carry information about the environment and can influence cellular decision-making in ways that are poorly understood. For example, it is unclear how the timing of individual phage infections affects the lysis-lysogeny decision of bacteriophage λ despite variable infection times being likely in the wild and even in laboratory conditions. In this work, we combine mathematical modeling with experimentation to address this question. We develop an experimentally testable theory, which reveals that late-infecting phages contribute less to cellular decision-making. This implies that infection delays lower the probability of lysogeny compared to simultaneous infections. Furthermore, we show that infection delays reduce lysogenization by providing insufficient CII for threshold crossing during the critical decision-making period. We find evidence for a cutoff time after which subsequent infections cannot influence the cellular decision. We derive an intuitive formula that approximates the probability of lysogeny for variable infection times by a time-weighted average of probabilities for simultaneous infections. We validate these theoretical predictions experimentally. Similar concepts and simplifying modeling approaches may help elucidate the mechanisms underlying other cellular decisions.
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27
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Visualization of phage DNA degradation by a type I CRISPR-Cas system at the single-cell level. QUANTITATIVE BIOLOGY 2017; 5:67-75. [PMID: 29119038 DOI: 10.1007/s40484-017-0099-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Background The CRISPR-Cas system is a widespread prokaryotic defense system which targets and cleaves invasive nucleic acids, such as plasmids or viruses. So far, a great number of studies have focused on the components and mechanisms of this system, however, a direct visualization of CRISPR-Cas degrading invading DNA in real-time has not yet been studied at the single-cell level. Methods In this study, we fluorescently label phage lambda DNA in vivo, and track the labeled DNA over time to characterize DNA degradation at the single-cell level. Results At the bulk level, the lysogenization frequency of cells harboring CRISPR plasmids decreases significantly compared to cells with a non-CRISPR control. At the single-cell level, host cells with CRISPR activity are unperturbed by phage infection, maintaining normal growth like uninfected cells, where the efficiency of our anti-lambda CRISPR system is around 26%. During the course of time-lapse movies, the average fluorescence of invasive phage DNA in cells with CRISPR activity, decays more rapidly compared to cells without, and phage DNA is fully degraded by around 44 minutes on average. Moreover, the degradation appears to be independent of cell size or the phage DNA ejection site suggesting that Cas proteins are dispersed in sufficient quantities throughout the cell. Conclusions With the CRISPR-Cas visualization system we developed, we are able to examine and characterize how a CRISPR system degrades invading phage DNA at the single-cell level. This work provides direct evidence and improves the current understanding on how CRISPR breaks down invading DNA.
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Linna RP, Suhonen PM, Piili J. Rigidity-induced scale invariance in polymer ejection from capsid. Phys Rev E 2017; 96:052402. [PMID: 29347730 DOI: 10.1103/physreve.96.052402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Indexed: 06/07/2023]
Abstract
While the dynamics of a fully flexible polymer ejecting a capsid through a nanopore has been extensively studied, the ejection dynamics of semiflexible polymers has not been properly characterized. Here we report results from simulations of ejection dynamics of semiflexible polymers ejecting from spherical capsids. Ejections start from strongly confined polymer conformations of constant initial monomer density. We find that, unlike for fully flexible polymers, for semiflexible polymers the force measured at the pore does not show a direct relation to the instantaneous ejection velocity. The cumulative waiting time t(s), that is, the time at which a monomer s exits the capsid the last time, shows a clear change when increasing the polymer rigidity κ. The major part of an ejecting polymer is driven out of the capsid by internal pressure. At the final stage the polymer escapes the capsid by diffusion. For the driven part there is a crossover from essentially exponential growth of t with s of the fully flexible polymers to a scale-invariant form. In addition, a clear dependence of t on polymer length N_{0} was found. These findings combined give the dependence t(s)∝N_{0}^{0.55}s^{1.33} for the strongly rigid polymers. This crossover in dynamics where κ acts as a control parameter is reminiscent of a phase transition. This analogy is further enhanced by our finding a perfect data collapse of t for polymers of different N_{0} and any constant κ.
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Affiliation(s)
- R P Linna
- Department of Computer Science, Aalto University, P.O. Box 15400, FI-00076 Aalto, Finland
| | - P M Suhonen
- Department of Computer Science, Aalto University, P.O. Box 15400, FI-00076 Aalto, Finland
| | - J Piili
- Department of Computer Science, Aalto University, P.O. Box 15400, FI-00076 Aalto, Finland
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29
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Zhou Y, Marar A, Kner P, Ramasamy RP. Charge-Directed Immobilization of Bacteriophage on Nanostructured Electrode for Whole-Cell Electrochemical Biosensors. Anal Chem 2017; 89:5734-5741. [PMID: 28485143 DOI: 10.1021/acs.analchem.6b03751] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A new type of carbon nanotube (CNT)-based impedimetric biosensing method has been developed for rapid and selective detection of live bacterial cells. A proof-of-concept study was conducted using T2 bacteriophage-based biosensors for electrochemical detection of Escherichia coli B. The T2 bacteriophage (virus) served as the biorecognition element, which was immobilized on polyethylenimine (PEI)-functionalized carbon nanotube transducer on glassy carbon electrode. Charge-directed, orientated immobilization of bacteriophage particles on carbon nanotubes was achieved through covalent linkage of phage capsid onto the carbon nanotubes. The presence of the immobilized phage on carbon nanotube-modified electrode was confirmed by fluorescence microscopy. Electrochemical impedance spectroscopy (EIS) was used to monitor the changes in the interfacial impedance due to the binding of E. coli B to T2 phage on the CNT-modified electrode. The detection was highly selective toward the B strain of E. coli as no signal was observed for the nonhost K strain of E. coli. The present achievable detection limit of the biosensor is 103 CFU/mL.
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Affiliation(s)
- Yan Zhou
- Nano Electrochemistry Laboratory, School of Chemical, Materials and Biomedical Engineering; ‡Department of Chemistry; and §School of Electrical and Computer Engineering, University of Georgia , Athens, Georgia 30602, United States
| | - Abhijit Marar
- Nano Electrochemistry Laboratory, School of Chemical, Materials and Biomedical Engineering; ‡Department of Chemistry; and §School of Electrical and Computer Engineering, University of Georgia , Athens, Georgia 30602, United States
| | - Peter Kner
- Nano Electrochemistry Laboratory, School of Chemical, Materials and Biomedical Engineering; ‡Department of Chemistry; and §School of Electrical and Computer Engineering, University of Georgia , Athens, Georgia 30602, United States
| | - Ramaraja P Ramasamy
- Nano Electrochemistry Laboratory, School of Chemical, Materials and Biomedical Engineering; ‡Department of Chemistry; and §School of Electrical and Computer Engineering, University of Georgia , Athens, Georgia 30602, United States
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CRISPR-Cas systems exploit viral DNA injection to establish and maintain adaptive immunity. Nature 2017; 544:101-104. [PMID: 28355179 PMCID: PMC5540373 DOI: 10.1038/nature21719] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 02/22/2017] [Indexed: 12/19/2022]
Abstract
CRISPR-Cas systems provide protection against viral1 and plasmid2 infection by capturing short DNA sequences from these invaders and integrating them into the CRISPR locus of the prokaryotic host1. These sequences, known as spacers, are transcribed into short RNA guides3–5 that specify the cleavage site of Cas nucleases in the genome of the invader6–8. When spacer sequences are acquired during viral infection is not known. To investigate this, we followed spacer acquisition in Staphylococcus aureus cells harboring a type II CRISPR-Cas9 system after infection with the staphylococcal bacteriophage ϕ12. We found that new spacers are acquired immediately following infection preferentially from the cos site, the viral free DNA end that is first injected into the cell. Analysis of spacer acquisition after infection with mutant phages demonstrated that most spacers are acquired during DNA injection, but not during other stages of the viral cycle that produce free DNA ends, such as DNA replication or packaging. Finally, we showed that spacers acquired from early-injected genomic regions, which direct Cas9 cleavage of the viral DNA immediately after infection, provide better immunity than spacers acquired from late-injected regions. Our results reveal that CRISPR-Cas systems exploit the phage life cycle to generate a pattern of spacer acquisition that ensures the success of the CRISPR immune response.
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31
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Trinh JT, Székely T, Shao Q, Balázsi G, Zeng L. Cell fate decisions emerge as phages cooperate or compete inside their host. Nat Commun 2017; 8:14341. [PMID: 28165024 PMCID: PMC5303824 DOI: 10.1038/ncomms14341] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 12/19/2016] [Indexed: 01/02/2023] Open
Abstract
The system of the bacterium Escherichia coli and its virus, bacteriophage lambda, is paradigmatic for gene regulation in cell-fate development, yet insight about its mechanisms and complexities are limited due to insufficient resolution of study. Here we develop a 4-colour fluorescence reporter system at the single-virus level, combined with computational models to unravel both the interactions between phages and how individual phages determine cellular fates. We find that phages cooperate during lysogenization, compete among each other during lysis, and that confusion between the two pathways occasionally occurs. Additionally, we observe that phage DNAs have fluctuating cellular arrival times and vie for resources to replicate, enabling the interplay during different developmental paths, where each phage genome may make an individual decision. These varied strategies could separate the selection for replication-optimizing beneficial mutations during lysis from sequence diversification during lysogeny, allowing rapid adaptation of phage populations for various environments.
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Affiliation(s)
- Jimmy T. Trinh
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
- Center for Phage Technology, Texas A&M University, College Station, Texas 77843, USA
| | - Tamás Székely
- The Louis and Beatrice Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, New York 11794, USA
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York 11794, USA
| | - Qiuyan Shao
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
- Center for Phage Technology, Texas A&M University, College Station, Texas 77843, USA
| | - Gábor Balázsi
- The Louis and Beatrice Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, New York 11794, USA
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York 11794, USA
| | - Lanying Zeng
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
- Center for Phage Technology, Texas A&M University, College Station, Texas 77843, USA
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32
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Acquisition of Phage Sensitivity by Bacteria through Exchange of Phage Receptors. Cell 2017; 168:186-199.e12. [DOI: 10.1016/j.cell.2016.12.003] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 09/29/2016] [Accepted: 12/01/2016] [Indexed: 12/14/2022]
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Affiliation(s)
- Ido Golding
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030;
- Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005
- Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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34
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Shao Q, Trinh JT, McIntosh CS, Christenson B, Balázsi G, Zeng L. Lysis-lysogeny coexistence: prophage integration during lytic development. Microbiologyopen 2016; 6. [PMID: 27530202 PMCID: PMC5300877 DOI: 10.1002/mbo3.395] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 06/30/2016] [Indexed: 11/11/2022] Open
Abstract
The infection of Escherichia coli cells by bacteriophage lambda results in bifurcated means of propagation, where the phage decides between the lytic and lysogenic pathways. Although traditionally thought to be mutually exclusive, increasing evidence suggests that this lysis-lysogeny decision is more complex than once believed, but exploring its intricacies requires an improved resolution of study. Here, with a newly developed fluorescent reporter system labeling single phage and E. coli DNAs, these two distinct pathways can be visualized by following the DNA movements in vivo. Surprisingly, we frequently observed an interesting "lyso-lysis" phenomenon in lytic cells, where phage integrates its DNA into the host, a characteristic event of the lysogenic pathway, followed by cell lysis. Furthermore, the frequency of lyso-lysis increases with the number of infecting phages, and specifically, with CII activity. Moreover, in lytic cells, the integration site attB on the E. coli genome migrates toward the polar region over time, leading to more spatial overlap with the phage DNA and frequent colocalization/collision of attB and phage DNA, possibly contributing to a higher chance for DNA integration.
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Affiliation(s)
- Qiuyan Shao
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA.,Center for Phage Technology, Texas A&M University, College Station, Texas, USA
| | - Jimmy T Trinh
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA.,Center for Phage Technology, Texas A&M University, College Station, Texas, USA
| | - Colby S McIntosh
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Brita Christenson
- Department of Biology and Biochemistry, University of Northwestern - St. Paul, St. Paul, Minnesota, USA
| | - Gábor Balázsi
- Laufer Center for Physical & Quantitative Biology, Stony Brook University, Stony Brook, New York, USA.,Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York, USA
| | - Lanying Zeng
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA.,Center for Phage Technology, Texas A&M University, College Station, Texas, USA
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Fernandes S, Labarde A, Baptista C, Jakutytè L, Tavares P, São-José C. A non-invasive method for studying viral DNA delivery to bacteria reveals key requirements for phage SPP1 DNA entry in Bacillus subtilis cells. Virology 2016; 495:79-91. [PMID: 27179995 DOI: 10.1016/j.virol.2016.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Revised: 04/30/2016] [Accepted: 05/05/2016] [Indexed: 12/26/2022]
Abstract
Bacteriophages use most frequently a tail apparatus to create a channel across the entire bacterial cell envelope to transfer the viral genome to the host cell cytoplasm, initiating infection. Characterization of this critical step remains a major challenge due to the difficulty to monitor DNA entry in the bacterium and its requirements. In this work we developed a new method to study phage DNA entry that has the potential to be extended to many tailed phages. Its application to study genome delivery of bacteriophage SPP1 into Bacillus subtilis disclosed a key role of the host cell membrane potential in the DNA entry process. An energized B. subtilis membrane and a millimolar concentration of calcium ions are shown to be major requirements for SPP1 DNA entry following the irreversible binding of phage particles to the receptor YueB.
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Affiliation(s)
- Sofia Fernandes
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Audrey Labarde
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, UMR 9198, 91198 Gif-sur-Yvette cedex, France; Unit of Molecular and Structural Virology (VMS), UPR3296 CNRS, Campus CNRS, 91198 Gif-sur-Yvette cedex, France
| | - Catarina Baptista
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Lina Jakutytè
- Unit of Molecular and Structural Virology (VMS), UPR3296 CNRS, Campus CNRS, 91198 Gif-sur-Yvette cedex, France
| | - Paulo Tavares
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, UMR 9198, 91198 Gif-sur-Yvette cedex, France; Unit of Molecular and Structural Virology (VMS), UPR3296 CNRS, Campus CNRS, 91198 Gif-sur-Yvette cedex, France
| | - Carlos São-José
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal.
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36
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Goldfain AM, Garmann RF, Jin Y, Lahini Y, Manoharan VN. Dynamic Measurements of the Position, Orientation, and DNA Content of Individual Unlabeled Bacteriophages. J Phys Chem B 2016; 120:6130-8. [DOI: 10.1021/acs.jpcb.6b02153] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
| | | | - Yan Jin
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
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37
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Shao Q, Hawkins A, Zeng L. Phage DNA dynamics in cells with different fates. Biophys J 2016; 108:2048-60. [PMID: 25902444 DOI: 10.1016/j.bpj.2015.03.027] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 02/24/2015] [Accepted: 03/17/2015] [Indexed: 11/27/2022] Open
Abstract
Bacteriophage λ begins its infection cycle by ejecting its DNA into its host Escherichia coli cell, after which either a lytic or a lysogenic pathway is followed, resulting in different cell fates. In this study, using a new technique to monitor the spatiotemporal dynamics of the phage DNA in vivo, we found that the phage DNA moves via two distinct modes, localized motion and motion spanning the whole cell. One or the other motion is preferred, depending on where the phage DNA is ejected into the cell. By examining the phage DNA trajectories, we found the motion to be subdiffusive. Moreover, phage DNA motion is the same in the early phase of the infection cycle, irrespective of whether the lytic or lysogenic pathway is followed; hence, cell-fate decision-making appears not to be correlated with the phage DNA motion. However, after the cell commits to one pathway or the other, phage DNA movement slows during the late phase of the lytic cycle, whereas it remains the same during the entire lysogenic cycle. Throughout the infection cycle, phage DNA prefers the regions around the quarter positions of the cell.
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Affiliation(s)
- Qiuyan Shao
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas; Center for Phage Technology, Texas A&M University, College Station, Texas
| | - Alexander Hawkins
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas; Center for Phage Technology, Texas A&M University, College Station, Texas
| | - Lanying Zeng
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas; Center for Phage Technology, Texas A&M University, College Station, Texas.
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38
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Marion S, Šiber A. Ejecting phage DNA against cellular turgor pressure. Biophys J 2015; 107:1924-1929. [PMID: 25418173 DOI: 10.1016/j.bpj.2014.09.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 09/01/2014] [Accepted: 09/05/2014] [Indexed: 11/25/2022] Open
Abstract
We examine in vivo ejection of noncondensed DNA from tailed bacteriophages into bacteria. The ejection is dominantly governed by the physical conditions in the bacteria. The confinement of the DNA in the virus capsid only slightly helps the ejection, becoming completely irrelevant during its last stages. A simple calculation based on the premise of condensed DNA in the cell enables us to estimate the maximal bacterial turgor pressure against which the ejection can still be fully realized. The calculated pressure (~5 atm) shows that the ejection of DNA into Gram-negative bacteria could proceed spontaneously, i.e., without the need to invoke active mechanisms.
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39
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Casjens SR, Hendrix RW. Bacteriophage lambda: Early pioneer and still relevant. Virology 2015; 479-480:310-30. [PMID: 25742714 PMCID: PMC4424060 DOI: 10.1016/j.virol.2015.02.010] [Citation(s) in RCA: 182] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/13/2015] [Accepted: 02/05/2015] [Indexed: 12/14/2022]
Abstract
Molecular genetic research on bacteriophage lambda carried out during its golden age from the mid-1950s to mid-1980s was critically important in the attainment of our current understanding of the sophisticated and complex mechanisms by which the expression of genes is controlled, of DNA virus assembly and of the molecular nature of lysogeny. The development of molecular cloning techniques, ironically instigated largely by phage lambda researchers, allowed many phage workers to switch their efforts to other biological systems. Nonetheless, since that time the ongoing study of lambda and its relatives has continued to give important new insights. In this review we give some relevant early history and describe recent developments in understanding the molecular biology of lambda's life cycle.
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Affiliation(s)
- Sherwood R Casjens
- Division of Microbiology and Immunology, Pathology Department, University of Utah School of Medicine, Emma Eccles Jones Medical Research Building, 15 North Medical Drive East, Salt Lake City, UT 84112, USA; Biology Department, University of Utah, Salt Lake City, UT 84112, USA.
| | - Roger W Hendrix
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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40
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Bacterial sensing of bacteriophages in communities: the search for the Rosetta stone. Curr Opin Microbiol 2014; 20:125-30. [DOI: 10.1016/j.mib.2014.05.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 05/19/2014] [Accepted: 05/20/2014] [Indexed: 01/21/2023]
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41
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Tal A, Arbel-Goren R, Costantino N, Court DL, Stavans J. Location of the unique integration site on an Escherichia coli chromosome by bacteriophage lambda DNA in vivo. Proc Natl Acad Sci U S A 2014; 111:7308-12. [PMID: 24799672 PMCID: PMC4034188 DOI: 10.1073/pnas.1324066111] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The search for specific sequences on long genomes is a key process in many biological contexts. How can specific target sequences be located with high efficiency, within physiologically relevant times? We addressed this question for viral integration, a fundamental mechanism of horizontal gene transfer driving prokaryotic evolution, using the infection of Escherichia coli bacteria with bacteriophage λ and following the establishment of a lysogenic state. Following the targeting process in individual live E. coli cells in real time revealed that λ DNA remains confined near the entry point of a cell following infection. The encounter between the 15-bp-long target sequence on the chromosome and the recombination site on the viral genome is facilitated by the directed motion of bacterial DNA generated during chromosome replication, in conjunction with constrained diffusion of phage DNA. Moving the native bacterial integration site to different locations on the genome and measuring the integration frequency in these strains reveals that the frequencies of the native site and a site symmetric to it relative to the origin are similar, whereas both are significantly higher than when the integration site is moved near the terminus, consistent with the replication-driven mechanism we propose. This novel search mechanism is yet another example of the exquisite coevolution of λ with its host.
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Affiliation(s)
- Asaf Tal
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel; and
| | - Rinat Arbel-Goren
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel; and
| | - Nina Costantino
- Gene Regulation and Chromosome Biology Laboratory, National Cancer Institute, Frederick, MD 21702-1201
| | - Donald L Court
- Gene Regulation and Chromosome Biology Laboratory, National Cancer Institute, Frederick, MD 21702-1201
| | - Joel Stavans
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel; and
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42
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Liu S, Chistol G, Hetherington CL, Tafoya S, Aathavan K, Schnitzbauer J, Grimes S, Jardine PJ, Bustamante C. A viral packaging motor varies its DNA rotation and step size to preserve subunit coordination as the capsid fills. Cell 2014; 157:702-713. [PMID: 24766813 PMCID: PMC4003460 DOI: 10.1016/j.cell.2014.02.034] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 01/05/2014] [Accepted: 02/15/2014] [Indexed: 11/18/2022]
Abstract
Multimeric, ring-shaped molecular motors rely on the coordinated action of their subunits to perform crucial biological functions. During these tasks, motors often change their operation in response to regulatory signals. Here, we investigate a viral packaging machine as it fills the capsid with DNA and encounters increasing internal pressure. We find that the motor rotates the DNA during packaging and that the rotation per base pair increases with filling. This change accompanies a reduction in the motor's step size. We propose that these adjustments preserve motor coordination by allowing one subunit to make periodic, specific, and regulatory contacts with the DNA. At high filling, we also observe the downregulation of the ATP-binding rate and the emergence of long-lived pauses, suggesting a throttling-down mechanism employed by the motor near the completion of packaging. This study illustrates how a biological motor adjusts its operation in response to changing conditions, while remaining highly coordinated.
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Affiliation(s)
- Shixin Liu
- Jason L. Choy Laboratory of Single Molecule Biophysics University of California, Berkeley, CA 94720, USA
- California Institute for Quantitative Biosciences University of California, Berkeley, CA 94720, USA
| | - Gheorghe Chistol
- Jason L. Choy Laboratory of Single Molecule Biophysics University of California, Berkeley, CA 94720, USA
- Department of Physics University of California, Berkeley, CA 94720, USA
| | - Craig L. Hetherington
- Jason L. Choy Laboratory of Single Molecule Biophysics University of California, Berkeley, CA 94720, USA
- California Institute for Quantitative Biosciences University of California, Berkeley, CA 94720, USA
- Department of Physics University of California, Berkeley, CA 94720, USA
| | - Sara Tafoya
- Jason L. Choy Laboratory of Single Molecule Biophysics University of California, Berkeley, CA 94720, USA
- Biophysics Graduate Group University of California, Berkeley, CA 94720, USA
| | - K. Aathavan
- Jason L. Choy Laboratory of Single Molecule Biophysics University of California, Berkeley, CA 94720, USA
- Biophysics Graduate Group University of California, Berkeley, CA 94720, USA
| | - Joerg Schnitzbauer
- Jason L. Choy Laboratory of Single Molecule Biophysics University of California, Berkeley, CA 94720, USA
- California Institute for Quantitative Biosciences University of California, Berkeley, CA 94720, USA
| | - Shelley Grimes
- Department of Diagnostic and Biological Sciences and Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Paul J. Jardine
- Department of Diagnostic and Biological Sciences and Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Carlos Bustamante
- Jason L. Choy Laboratory of Single Molecule Biophysics University of California, Berkeley, CA 94720, USA
- California Institute for Quantitative Biosciences University of California, Berkeley, CA 94720, USA
- Department of Physics University of California, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology, Department of Chemistry, and Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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Parent KN, Erb ML, Cardone G, Nguyen K, Gilcrease EB, Porcek NB, Pogliano J, Baker TS, Casjens SR. OmpA and OmpC are critical host factors for bacteriophage Sf6 entry in Shigella. Mol Microbiol 2014; 92:47-60. [PMID: 24673644 DOI: 10.1111/mmi.12536] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2014] [Indexed: 12/26/2022]
Abstract
Despite being essential for successful infection, the molecular cues involved in host recognition and genome transfer of viruses are not completely understood. Bacterial outer membrane proteins A and C co-purify in lipid vesicles with bacteriophage Sf6, implicating both outer membrane proteins as potential host receptors. We determined that outer membrane proteins A and C mediate Sf6 infection by dramatically increasing its rate and efficiency. We performed a combination of in vivo studies with three omp null mutants of Shigella flexneri, including classic phage plaque assays and time-lapse fluorescence microscopy to monitor genome ejection at the single virion level. Cryo-electron tomography of phage 'infecting' outer membrane vesicles shows the tail needle contacting and indenting the outer membrane. Lastly, in vitro ejection studies reveal that lipopolysaccharide and outer membrane proteins are both required for Sf6 genome release. We conclude that Sf6 phage entry utilizes either outer membrane proteins A or C, with outer membrane protein A being the preferred receptor.
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Affiliation(s)
- Kristin N Parent
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA; Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, CA, 92093, USA
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DE FRUTOS M, LEFORESTIER A, LIVOLANT F. RELATIONSHIP BETWEEN THE GENOME PACKING IN THE BACTERIOPHAGE CAPSID AND THE KINETICS OF DNA EJECTION. ACTA ACUST UNITED AC 2014. [DOI: 10.1142/s1793048013500069] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We present a general survey of experimental and theoretical observations of DNA structure and in vitro ejection kinetics for different bacteriophage species. In some species, like T5, the ejection may present pauses and arrests that have not been detected in others species like Lambda. We propose hypotheses to explain such differences and we discuss how the experimental conditions may be important for their detection. Our work highlights the role of DNA organization inside the bacteriophage capsid on the stochastic and out of equilibrium nature of the ejection process.
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Affiliation(s)
- M. DE FRUTOS
- Institut de Biologie et Biochimie Moléculaire et Cellulaire, UMR CNRS 8619, Bât 430, Université Paris Sud, 91405 Orsay cedex, France
| | - A. LEFORESTIER
- Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris-Sud, Bât 510, Orsay 91405, France
| | - F. LIVOLANT
- Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris-Sud, Bât 510, Orsay 91405, France
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Chiaruttini N, Letellier L, Viasnoff V. A novel method to couple electrophysiological measurements and fluorescence imaging of suspended lipid membranes: the example of T5 bacteriophage DNA ejection. PLoS One 2013; 8:e84376. [PMID: 24376806 PMCID: PMC3871697 DOI: 10.1371/journal.pone.0084376] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 11/22/2013] [Indexed: 12/21/2022] Open
Abstract
We present an innovative method to couple electrophysiological measurements with fluorescence imaging of functionalized suspended bilayers. Our method combines several advantages: it is well suited to study transmembrane proteins that are difficult to incorporate in suspended bilayers, it allows single molecule resolution both in terms of electrophysiological measurements and fluorescence imaging, and it enables mechanical stimulations of the membrane. The approach comprises of two steps: first the reconstitution of membrane proteins in giant unilamellar vesicles; then the formation of a suspended bilayer spanning a 5 to 15 micron-wide aperture that can be visualized by high NA microscope objectives. We exemplified how the technique can be used to detect in real time the translocation of T5 DNA across the bilayer during its ejection from the bacteriophage capsid.
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Affiliation(s)
- Nicolas Chiaruttini
- ESPCI Paristech, CNRS, Paris, France
- Aurélien Roux Lab, Biochemistry Department, University of Geneva, Geneva, Switzerland
| | - Lucienne Letellier
- Institut de Biochimie et Biophysique Moléculaire et Cellulaire, Université Paris Sud-11, CNRS, Orsay, France
| | - Virgile Viasnoff
- ESPCI Paristech, CNRS, Paris, France
- Aurélien Roux Lab, Biochemistry Department, University of Geneva, Geneva, Switzerland
- Institut de Biochimie et Biophysique Moléculaire et Cellulaire, Université Paris Sud-11, CNRS, Orsay, France
- MechanoBiology Institute of Singapore, Singapore, Singapore
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Leavitt JC, Gogokhia L, Gilcrease EB, Bhardwaj A, Cingolani G, Casjens SR. The tip of the tail needle affects the rate of DNA delivery by bacteriophage P22. PLoS One 2013; 8:e70936. [PMID: 23951045 PMCID: PMC3741392 DOI: 10.1371/journal.pone.0070936] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 06/25/2013] [Indexed: 02/01/2023] Open
Abstract
The P22-like bacteriophages have short tails. Their virions bind to their polysaccharide receptors through six trimeric tailspike proteins that surround the tail tip. These short tails also have a trimeric needle protein that extends beyond the tailspikes from the center of the tail tip, in a position that suggests that it should make first contact with the host’s outer membrane during the infection process. The base of the needle serves as a plug that keeps the DNA in the virion, but role of the needle during adsorption and DNA injection is not well understood. Among the P22-like phages are needle types with two completely different C-terminal distal tip domains. In the phage Sf6-type needle, unlike the other P22-type needle, the distal tip folds into a “knob” with a TNF-like fold, similar to the fiber knobs of bacteriophage PRD1 and Adenovirus. The phage HS1 knob is very similar to that of Sf6, and we report here its crystal structure which, like the Sf6 knob, contains three bound L-glutamate molecules. A chimeric P22 phage with a tail needle that contains the HS1 terminal knob efficiently infects the P22 host, Salmonella enterica, suggesting the knob does not confer host specificity. Likewise, mutations that should abrogate the binding of L-glutamate to the needle do not appear to affect virion function, but several different other genetic changes to the tip of the needle slow down potassium release from the host during infection. These findings suggest that the needle plays a role in phage P22 DNA delivery by controlling the kinetics of DNA ejection into the host.
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Affiliation(s)
- Justin C. Leavitt
- Biology Department, University of Utah, Salt Lake City, Utah, United States of America
| | - Lasha Gogokhia
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
| | - Eddie B. Gilcrease
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
| | - Anshul Bhardwaj
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Gino Cingolani
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Sherwood R. Casjens
- Biology Department, University of Utah, Salt Lake City, Utah, United States of America
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
- * E-mail:
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Mahalik JP, Hildebrandt B, Muthukumar M. Langevin dynamics simulation of DNA ejection from a phage. J Biol Phys 2013; 39:229-45. [PMID: 23860871 DOI: 10.1007/s10867-013-9316-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 03/22/2013] [Indexed: 11/30/2022] Open
Abstract
We have performed Langevin dynamics simulations of a coarse-grained model of ejection of dsDNA from Φ29 phage. Our simulation results show significant variations in the local ejection speed, consistent with experimental observations reported in the literature for both in vivo and in vitro systems. In efforts to understand the origin of such variations in the local speed of ejection, we have investigated the correlations between the local ejection kinetics and the packaged structures created at various motor forces and chain flexibility. At lower motor forces, the packaged DNA length is shorter with better organization. On the other hand, at higher motor forces typical of realistic situations, the DNA organization inside the capsid suffers from significant orientational disorder, but yet with long orientational correlation times. This in turn leads to lack of registry between the direction of the DNA segments just to be ejected and the direction of exit. As a result, a significant amount of momentum transfer is required locally for successful exit. Consequently, the DNA ejection temporarily slows down exhibiting pauses. This slowing down occurs at random times during the ejection process, completely determined by the particular starting conformation created by prescribed motor forces. In order to augment our inference, we have additionally investigated the ejection of chains with deliberately changed persistence length. For less inflexible chains, the demand on the occurrence of large momentum transfer for successful ejection is weaker, resulting in more uniform ejection kinetics. While being consistent with experimental observations, our results show the nonergodic nature of the ejection kinetics and call for better theoretical models to portray the kinetics of genome ejection from phages.
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Affiliation(s)
- J P Mahalik
- Department of Polymer Science and Engineering, Department of Physics, University of Massachusetts, Amherst, MA 01003, USA
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Abstract
Sixty years after Hershey and Chase showed that nucleic acid is the major component of phage particles that is ejected into cells, we still do not fully understand how the process occurs. Advances in electron microscopy have revealed the structure of the condensed DNA confined in a phage capsid, and the mechanisms and energetics of packaging a phage genome are beginning to be better understood. Condensing DNA subjects it to high osmotic pressure, which has been suggested to provide the driving force for its ejection during infection. However, forces internal to a phage capsid cannot, alone, cause complete genome ejection into cells. Here, we describe the structure of the DNA inside mature phages and summarize the current models of genome ejection, both in vitro and in vivo.
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Affiliation(s)
- Ian J Molineux
- Molecular Genetics and Microbiology, Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
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Ghosal S. Capstan friction model for DNA ejection from bacteriophages. PHYSICAL REVIEW LETTERS 2012; 109:248105. [PMID: 23368388 PMCID: PMC3707003 DOI: 10.1103/physrevlett.109.248105] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Indexed: 06/01/2023]
Abstract
Bacteriophages infect cells by attaching to the outer membrane and injecting their DNA into the cell. The phage DNA is then transcribed by the cell's transcription machinery. A number of physical mechanisms by which DNA can be translocated from the phage capsid into the cell have been identified. A fast ejection driven by the elastic and electrostatic potential energy of the compacted DNA within the viral capsid appears to be used by most phages, at least to initiate infection. In recent in vitro experiments, the speed of DNA translocation from a λ phage capsid has been measured as a function of ejected length over the entire duration of the event. Here, a mechanical model is proposed that is able to explain the observed dependence of exit velocity on ejected length, and that is also consistent with the accepted picture of the geometric arrangement of DNA within the viral capsid.
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Affiliation(s)
- Sandip Ghosal
- Department of Physics, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
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