RESUMEN
Phage-induced lysis of Gram-negative bacterial hosts usually requires a set of phage lysis proteins, a holin, an endopeptidase, and a spanin system, to disrupt each of the three cell envelope layers. Genome annotations and previous studies identified a gene region in the Shewanella oneidensis prophage LambdaSo, which comprises potential holin- and endolysin-encoding genes but lacks an obvious spanin system. By a combination of candidate approaches, mutant screening, characterization, and microscopy, we found that LambdaSo uses a pinholin/signal-anchor-release (SAR) endolysin system to induce proton leakage and degradation of the cell wall. Between the corresponding genes, we found that two extensively nested open-reading frames encode a two-component spanin module Rz/Rz1. Unexpectedly, we identified another factor strictly required for LambdaSo-induced cell lysis, the phage protein Lcc6. Lcc6 is a transmembrane protein of 65 amino acid residues with hitherto unknown function, which acts at the level of holin in the cytoplasmic membrane to allow endolysin release. Thus, LambdaSo-mediated cell lysis requires at least four protein factors (pinholin, SAR endolysin, spanin, and Lcc6). The findings further extend the known repertoire of phage proteins involved in host lysis and phage egress. IMPORTANCE: Lysis of bacteria can have multiple consequences, such as the release of host DNA to foster robust biofilm. Phage-induced lysis of Gram-negative cells requires the disruption of three layers, the outer and inner membranes and the cell wall. In most cases, the lysis systems of phages infecting Gram-negative cells comprise holins to disrupt or depolarize the membrane, thereby releasing or activating endolysins, which then degrade the cell wall. This, in turn, allows the spanins to become active and fuse outer and inner membranes, completing cell envelope disruption and allowing phage egress. Here, we show that the presence of these three components may not be sufficient to allow cell lysis, implicating that also in known phages, further factors may be required.
Asunto(s)
Bacteriólisis , Endopeptidasas , Shewanella , Shewanella/virología , Shewanella/genética , Endopeptidasas/metabolismo , Endopeptidasas/genética , Proteínas Virales/metabolismo , Proteínas Virales/genética , Bacteriófago lambda/fisiología , Bacteriófago lambda/genéticaRESUMEN
Bacterial viruses (phages) are potent agents of lateral gene transfer and thus are important drivers of evolution. A group of mobile genetic elements, referred to as phage satellites, exploits phages to disseminate their own genetic material. Here, we isolated a novel member of the family Inoviridae, Shewanella phage Dolos, along with an autonomously replicating plasmid, pDolos. Dolos causes a chronic infection in its host Shewanella oneidensis by phage production with only minor effects on the host cell proliferation. When present, plasmid pDolos hijacks Dolos functions to be predominantly packaged into phage virions and released into the environment and, thus, acts as a phage satellite. pDolos can disseminate further genetic material encoding, e.g., resistances or fluorophores to host cells sensitive to Dolos infection. Given the rather simple requirements of a plasmid for takeover of an inovirus and the wide distribution of phages of this group, we speculate that similar phage-satellite systems are common among bacteria.IMPORTANCEPhage satellites are mobile genetic elements, which hijack phages to be transferred to other host cells. The vast majority of these phage satellites integrate within the host's chromosome, and they all carry remaining phage genes. Here, we identified a novel phage satellite, pDolos, which uses an inovirus for dissemination. pDolos (i) remains as an autonomously replicating plasmid within its host, (ii) does not carry recognizable phage genes, and (iii) is smaller than any other phage satellites identified so far. Thus, pDolos is the first member of a new class of phage satellites, which resemble natural versions of phagemids.
Asunto(s)
Plásmidos , Shewanella , Plásmidos/genética , Shewanella/virología , Shewanella/genética , Inovirus/genética , Virus Satélites/genética , Genoma Viral , Bacteriófagos/genética , Bacteriófagos/clasificación , Bacteriófagos/aislamiento & purificaciónRESUMEN
Quorum sensing (QS) plays an important role in phage-host interactions. Shewanella baltica can't produce the N-acyl-homoserine lactones (AHLs) signal molecules but can eavesdrop on exogenous AHLs through its LuxR receptor. However, no clear evidence exists regarding the involvement of AHLs-mediated QS systems in S. baltica in regulating phage infection. Here, we report that AHLs modulated the phage resistance of S. baltica OS155. Specifically, we characterized a S. baltica phage vB_Sb_QDWS and preliminarily identified that lipopolysaccharide (LPS) is an important receptor for phage vB_Sb_QDWS. AHLs could protect S. baltica against phage infection by decreasing LPS-mediated phage adsorption. The expression of genes galU and tkt, which are essential for LPS synthesis, down-regulated significantly in response to AHLs autoinducers. Our finding confirms the important roles of QS in virus-host interactions and would be helpful to develop novel phage strategies for food spoilage control.
Asunto(s)
Acil-Butirolactonas , Proteínas Bacterianas , Bacteriófagos , Shewanella , Transactivadores , Percepción de Quorum , Shewanella/metabolismo , Shewanella/virología , Transducción de Señal , Acil-Butirolactonas/metabolismo , Proteínas Represoras/metabolismo , Transactivadores/metabolismo , Bacteriófagos/fisiología , Acoplamiento Viral , Receptores Virales/metabolismo , Proteínas Bacterianas/metabolismo , Lipopolisacáridos/metabolismo , Expresión GénicaRESUMEN
Shewanella is a ubiquitous bacterial genus of aquatic ecosystems, and its bacteriophages are also isolated from aquatic environments (oceans, lakes, ice, and wastewater). In this study, the isolation and characterization of a novel virulent Shewanella phage vB_SspS_KASIA and the identification of three prophages of its host, Shewanella sp. M16, including a mitomycin-inducible Mu-like siphovirus, vB_SspS_MuM16-1, became the starting point for comparative analyses of phages infecting Shewanella spp. and the determination of their position among the known bacterial viruses. A similarity networking analysis revealed the high diversity of Shewanella phages in general, with vB_SspS_KASIA clustering exclusively with Colwellia phage 9A, with which it forms a single viral cluster composed of two separate viral subclusters. Furthermore, vB_SspS_MuM16-1 presented itself as being significantly different from the phages deposited in public databases, expanding the diversity of the known Mu-like phages and giving potential molecular markers for the identification of Mu-like prophages in bacterial genomes. Moreover, the functional analysis performed for vB_SspS_KASIA suggested that, despite the KASIA host, the M16 strain grows better in a rich medium and at 30 °C the phage replication cycle seems to be optimal in restrictive culture conditions mimicking their natural environment, the Zloty Stok gold and arsenic mine.
Asunto(s)
Bacteriófagos/genética , Genoma Viral , Profagos/genética , Shewanella/virología , Bacteriófagos/patogenicidad , Hibridación Genómica Comparativa , ADN Viral/química , ADN Viral/genética , ADN Viral/metabolismo , ARN Polimerasas Dirigidas por ADN/genética , ARN Polimerasas Dirigidas por ADN/metabolismo , Variación Genética , Intrones , Profagos/patogenicidad , Análisis de Secuencia de ADN , Proteínas Virales/genética , Proteínas Virales/metabolismo , Virulencia/genéticaRESUMEN
Viruses, especially bacteriophages, are thought to have important functions in the deep-sea ecosystem, but little is known about the induction mechanism of benthic phages in response to environmental change. Our prior work characterized a cold-active filamentous phage SW1 that infects the deep-sea bacterium Shewanella piezotolerans WP3; however, the underlying mechanism of the putative thermo-regulated genetic switch of SW1 is still unclear. In this study, the DNA copy number and mRNA abundance of the deep-sea phage SW1 were quantified in the whole life cycle of its host S. piezotolerans WP3 at different temperatures. Our results demonstrated that the induction of SW1 is dependent on a threshold temperature (4°C), but this dependency is not proportional to temperature gradient. RNA-Seq analyses revealed two highly transcribed regions at 4°C and verified the presence of a long 3' untranslated region (UTR) in the SW1 genome. Interestingly, recruitment analysis showed that SW1-like inoviruses prevail in deep sea (depth >1000 m) and photic epipelagic and mesopelagic zones (depth <1000 m), which suggested that the thermo-regulated genetic switch revealed in SW1 may be widely distributed in the ocean.
Asunto(s)
Bacteriófagos/genética , Genoma Viral , Shewanella , Temperatura , Genes de Cambio , Genoma Viral/genética , Océano Pacífico , Agua de Mar , Shewanella/virologíaRESUMEN
The coastal sediments were considered to contain diverse phages playing important roles in driving biogeochemical cycles based on genetic analysis. However, till now, benthic phages in coastal sediments were very rarely isolated, which largely limits our understanding of their biological characteristics. Here, we describe a novel lytic phage (named Shewanella phage S0112) isolated from the coastal sediments of the Yellow Sea infecting a sediment bacterium of the genus Shewanella. The phage has a very high replication capability, with the burst size of ca. 1170 phage particles per infected cell, which is 5-10 times higher than that of most phages isolated before. Meanwhile, the latent period of this phage is relatively longer, which might ensure adequate time for phage replication. The phage has a double-stranded DNA genome comprising 62,286 bp with 102 ORFs, ca. 60% of which are functionally unknown. The expression products of 16 ORF genes, mainly structural proteins, were identified by LC-MS/MS analysis. Besides the general DNA metabolism and structure assembly genes in the phage genome, there is a cluster of auxiliary metabolic genes that may be involved in 7-cyano-7-deazaguanine (preQ0) biosynthesis. Meanwhile, a pyrophosphohydrolase (MazG) gene being considered as a regulator of programmed cell death or involving in host stringer responses is inserted in this gene cluster. Comparative genomic and phylogenetic analysis both revealed a great novelty of phage S0112. This study represents the first report of a benthic phage infecting Shewanella, which also sheds light on the phage-host interactions in coastal sediments.
Asunto(s)
Bacteriófagos/fisiología , Interacciones Huésped-Patógeno , Shewanella/virología , Replicación Viral , Bacteriófagos/ultraestructura , Cromatografía Liquida , Genes Virales , Genoma Viral , Genómica/métodos , Especificidad del Huésped , Sistemas de Lectura Abierta , Filogenia , Análisis de Secuencia de ADN , Espectrometría de Masas en Tándem , Virión/ultraestructuraRESUMEN
Many bacterial genomes carry multiple prophages that compete with each other, potentially affecting the physiology, fitness, and pathogenicity of their hosts. However, molecular mechanisms of such prophage-prophage conflicts remain poorly understood. The genome of Shewanella oneidensis MR-1, a Gammaproteobacterium residing in aquatic environments and notable for its ability to reduce metal ions, harbours four prophages, two of which (LambdaSo and MuSo2) form infectious virions during biofilm formation. Here, we constructed indicator strains of LambdaSo and MuSo2 by deleting the corresponding prophages from the MR-1 chromosome and investigated their reproduction. Interestingly, the fitness of MuSo2 increased in the absence of LambdaSo, suggesting that prophage LambdaSo repressed MuSo2 reproduction. Partial deletion of LambdaSo from the MR-1 chromosome revealed that gene cluster R of LambdaSo, which was responsible for the switch to the lytic cycle and LambdaSo genome replication initiation, was necessary and sufficient to repress MuSo2. Furthermore, activation of cluster R genes facilitated replication of cluster R-encoding DNA and inhibited host and MuSo2 DNA replication. These findings suggest that LambdaSo represses MuSo2 propagation by inhibiting DNA replication during simultaneous induction. We predict that such a mechanism of inter-prophage interference is more widespread in bacteria than currently appreciated.
Asunto(s)
Bacteriófagos/fisiología , Profagos/genética , Shewanella/virología , Bacteriófagos/clasificación , Bacteriófagos/genética , Profagos/clasificación , Profagos/fisiología , Replicación ViralRESUMEN
The growth of Shewanella spp., mainly S. baltica and S. putrefaciens, is responsible for the spoilage of chilled fresh fish. Phages are an alternative tool to control bacterial growth. In this study, virulent phages infecting 4 S. baltica and 6 S. putrefaciens strains were isolated and characterized. Transmission electron microscopy revealed that 6 out of 10 phages (3 phages infecting S. baltica and 3 phages infecting S. putrefaciens) belonged to Myoviridae, while the other 4 phages (1 phage infecting S. baltica and 3 phages infecting S. putrefaciens) belonged to Siphoviridae. Phage SppYZU01 and SppYZU05 showed the broadest host range, being lytic towards all the 4 S. baltica strains and 5 out of the 6 S. putrefaciens strains, respectively. The genome sequence of SppYZU01 had no similarity with known genome sequences, while that of SppYZU05 was 88.5% similar to the genome of a virulent S. putrefaciens-infecting phage (Spp001). According to the host range and lytic activity, 3 phages, including SppYZU01, SppYZU05, and SppYZU06, were combined into a cocktail (designated as SPMIX3-156). SPMIX3-156 showed potential as an antimicrobial agent to control S. baltica and S. putrefaciens strain growth in catfish matrices. Bacterial growth in the catfish muscle juice inoculated with 104 colony-forming units (CFU)/mL of Shewanella strains was partially inhibited by 105 plaque-forming units (PFU)/mL of SPMIX3-156 at both 25⯰C and 4⯰C. The catfish fillets inoculated with Shewanella strains were used as a model to evaluate the biopreservative effects of SPMIX3-156. Total viable counts of fillet samples treated with 107 PFU/mL of SPMIX3-156 were reduced by 3.21 and 2.75 log units after 1â¯day at 25⯰C and 10â¯day at 4⯰C, respectively, compared to those of untreated samples. Fillet quality indices, including pH, total volatile basic nitrogen, and sensory value of the SPMIX3-156-treated samples, considerably improved compared to those of the control samples at both 4⯰C and 25⯰C. Our results suggest that SPMIX3-156 is a promising biological agent against S. baltica and S. putrefaciens, and may have a potential use in chilled fish fillet biopreservation.
Asunto(s)
Bacteriófagos/genética , Genes Virales , Ictaluridae/microbiología , Shewanella putrefaciens/virología , Shewanella/virología , Animales , Bacteriófagos/aislamiento & purificación , Agentes de Control Biológico , Recuento de Colonia Microbiana , ADN Viral/aislamiento & purificación , Contaminación de Alimentos , Microbiología de Alimentos , Conservación de Alimentos , Myoviridae/aislamiento & purificación , Alimentos Marinos/microbiología , Análisis de Secuencia de ADN , Siphoviridae/aislamiento & purificaciónRESUMEN
Outnumbering all other biological entities on earth, bacteriophages (phages) play critical roles in structuring microbial communities through bacterial infection and subsequent lysis, as well as through horizontal gene transfer. While numerous studies have examined the effects of phages on free-living bacterial cells, much less is known regarding the role of phage infection in host-associated biofilms, which help to stabilize adherent microbial communities. Here we report the cultivation and characterization of a novel strain of Shewanella fidelis from the gut of the marine tunicate Ciona intestinalis, inducible prophages from the S. fidelis genome, and a strain-specific lytic phage recovered from surrounding seawater. In vitro biofilm assays demonstrated that lytic phage infection affects biofilm formation in a process likely influenced by the accumulation and integration of the extracellular DNA released during cell lysis, similar to the mechanism that has been previously shown for prophage induction.
Asunto(s)
Bacteriófagos/crecimiento & desarrollo , Bacteriófagos/aislamiento & purificación , Ciona intestinalis/microbiología , Ciona intestinalis/virología , Shewanella/aislamiento & purificación , Shewanella/virología , Animales , Bacteriólisis , Biopelículas/crecimiento & desarrollo , Intestinos/microbiología , Intestinos/virología , Shewanella/fisiologíaRESUMEN
Among the environmental stresses experienced by bacteria, temperature shifts are one of the most important. In this study, we discovered a novel cold adaptation mechanism in Shewanella oneidensis that occurs at the DNA level and is regulated by cryptic prophage excision. Previous studies on bacterial cold tolerance mainly focus on the structural change of cell membrane and changes at the RNA and protein levels. Whether or not genomic change can also contribute to this process has not been explored. Here we employed a whole-genome deep-sequencing method to probe the changes at DNA level in a model psychrotrophic bacteria strain. We found that temperature downshift induced a 10 000-fold increase of the excision of a novel P4-like cryptic prophage. Importantly, although prophage excision only occurred in a relatively small population of bacteria, it was able to facilitate biofilm formation and promote the survival of the entire population. This prophage excision affected cell physiology by disrupting a critical gene encoding transfer-messenger RNA (tmRNA). In addition, we found that the histone-like nucleoid-structuring protein (H-NS) could silence prophage excision via binding to the promoter of the putative excisionase gene at warm temperatures. H-NS level was reduced at cold temperatures, leading to de-repression of prophage excision. Collectively, our results reveal that cryptic prophage excision acts as a regulatory switch to enable the survival of the host at low temperature by controlling the activity of tmRNA and biofilm formation.
Asunto(s)
Profagos/fisiología , Shewanella/fisiología , Shewanella/virología , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Frío , ADN Nucleotidiltransferasas/genética , ADN Nucleotidiltransferasas/metabolismo , Profagos/genética , Shewanella/genética , Proteínas Virales/genética , Proteínas Virales/metabolismo , Activación ViralRESUMEN
Antibiotic selection drives adaptation of antibiotic resistance plasmids to new bacterial hosts, but the molecular mechanisms are still poorly understood. We previously showed that a broad-host-range plasmid was poorly maintained in Shewanella oneidensis, but rapidly adapted through mutations in the replication initiation gene trfA1. Here we examined if these mutations reduced the fitness cost of TrfA1, and whether this was due to changes in interaction with the host's DNA helicase DnaB. The strains expressing evolved TrfA1 variants showed a higher growth rate than those expressing ancestral TrfA1. The evolved TrfA1 variants showed a lower affinity to the helicase than ancestral TrfA1 and were no longer able to activate the helicase at the oriV without host DnaA. Moreover, persistence of the ancestral plasmid was increased upon overexpression of DnaB. Finally, the evolved TrfA1 variants generated higher plasmid copy numbers than ancestral TrfA1. The findings suggest that ancestral plasmid instability can at least partly be explained by titration of DnaB by TrfA1. Thus under antibiotic selection resistance plasmids can adapt to a novel bacterial host through partial loss of function mutations that simultaneously increase plasmid copy number and decrease unfavorably high affinity to one of the hosts' essential proteins.
Asunto(s)
Proteínas de Escherichia coli/metabolismo , Plásmidos/metabolismo , Shewanella/virología , ADN Helicasas/metabolismo , Replicación del ADN/genética , Proteínas de Unión al ADN/metabolismo , AdnB Helicasas/genética , AdnB Helicasas/metabolismo , Farmacorresistencia Microbiana , Escherichia coli/genética , Escherichia coli/metabolismo , Escherichia coli/virología , Proteínas de Escherichia coli/genética , Plásmidos/genética , Shewanella/genéticaRESUMEN
As the most abundant biological entities on the planet, viruses are involved in global biogeochemical cycles, and they have been shown to play an important role in the overall functioning of the deep-sea ecosystem. Nevertheless, little is known about whether and how deep-sea viruses affect the physiology of their bacterial hosts. Previously, the filamentous phage SW1 was identified in the bathypelagic bacterium Shewanella piezotolerans WP3, which was isolated from the upper sediment of West Pacific ocean. In this study, phage SW1 was shown to be active under in situ environmental conditions (20 MPa and 4°C) by transmission electron microscopy and reverse-transcription quantitative polymerase chain reaction. Further comparative analysis showed that SW1 had a significant influence on the growth and transcriptome of its host. The transcription of genes responsible for basic cellular activities, including the transcriptional/translational apparatus, arginine synthesis, purine metabolism and the flagellar motor, were down-regulated by the phage. Our results present the first characterization of a phage-host interaction under high-pressure and low-temperature conditions, which indicated that the phage adjusted the energy utilization strategy of the host for improved survival in deep-sea environments.
Asunto(s)
Frío , Perfilación de la Expresión Génica , Presión Hidrostática , Inovirus/crecimiento & desarrollo , Shewanella/genética , Shewanella/virología , Sedimentos Geológicos , Interacciones Huésped-Parásitos , Microscopía Electrónica de Transmisión , Océano Pacífico , Reacción en Cadena en Tiempo Real de la Polimerasa , Shewanella/crecimiento & desarrollo , Shewanella/efectos de la radiaciónRESUMEN
Virus production in the deep-sea environment has been found to be high, and viruses have been suggested to play significant roles in the overall functioning of this ecosystem. Nevertheless, little is known about these viruses, including the mechanisms that control their production, which makes them one of the least understood biological entities on Earth. Previously, we isolated the filamentous phage SW1, whose virus production and gene transcription were found to be active at low temperatures, from a deep-sea bacterium, Shewanella piezotolerans WP3. In this study, the operon structure of phage SW1 is presented, which shows two operons with exceptionally long 5' and 3' untranslated regions (UTRs). In addition, the 5'UTR was confirmed to significantly influence the RNA stability of the SW1 transcripts. Our study revealed novel regulation of the operon and led us to propose a unique regulatory mechanism for Inoviruses. This type of RNA-based regulation may represent a mechanism for significant viral production in the cold deep biosphere.
Asunto(s)
Inovirus/genética , ARN Viral/genética , Shewanella/virología , Regiones no Traducidas 5' , Secuencia de Bases , Regulación Viral de la Expresión Génica , Genes Virales , Operón , Regiones Promotoras Genéticas , Unión Proteica , Estabilidad del ARN , ARN Viral/metabolismo , Análisis de Secuencia de ARN , Shewanella/genética , Proteínas Virales/fisiologíaRESUMEN
A low-temperature-inducible protein expression vector (pSW2) based on a filamentous phage (SW1) of the deep-sea bacterium Shewanella piezotolerans WP3 was constructed. This vector replicated stably in Escherichia coli and Shewanella species, and its copy number increased at low temperatures. The pSW2 vector can be utilized as a complementation plasmid in WP3, and it can also be used for the production of complex cytochromes with multiple heme groups, which has the potential for application for metal ion recovery or bioremediation. Promoters of low-temperature-inducible genes in WP3 were fused into the vector to construct a series of vectors for enhancing protein expression at low temperature. The maximum green fluorescent protein intensity was obtained when the promoter for the hfq gene was used. The WP3/pSW2 system can efficiently produce a patatin-like protein (PLP) from a metagenomic library that tends to form inclusion bodies in E. coli. The yields of PLP in the soluble fraction were 8.3 mg/liter and 4.7 mg/liter of culture at 4°C and 20°C, respectively. Moreover, the pSW2 vector can be broadly utilized in other Shewanella species, such as S. oneidensis and S. psychrophila.
Asunto(s)
Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica/efectos de la radiación , Vectores Genéticos , Inovirus/genética , Plásmidos , Shewanella/genética , Shewanella/virología , Fusión Artificial Génica , Replicación del ADN , Genes Reporteros , Genética Microbiana/métodos , Proteínas Fluorescentes Verdes/análisis , Proteínas Fluorescentes Verdes/genética , Inovirus/aislamiento & purificación , Biología Molecular/métodos , Regiones Promotoras Genéticas , Recombinación Genética , TemperaturaRESUMEN
Heterotrophic bacteria are the major prokaryotic component of the Baltic Sea ice microbiome, and it is postulated that phages are among their major parasites. In this study, we sequenced the complete genomes of six earlier reported phage isolates from the Baltic Sea ice infecting Shewanella sp. and Flavobacterium sp. hosts as well as characterized the phage-host interactions. Based on the genome sequences, the six phages were classified into five new genera. Only two phages, 1/4 and 1/40, both infecting Shewanella sp. strains, showed significant nucleotide sequence similarity to each other and could be grouped into the same genus. These two phages are also related to Vibrio-specific phages sharing approximately 25% of the predicted gene products. Nevertheless, cross-titrations showed that the cold-active phages studied are host specific: none of the seven additionally tested, closely related Shewanella strains served as hosts for the phages. Adsorption experiments of two Shewanella phages, 1/4 and 3/49, conducted at 4 °C and at 15 °C revealed relatively fast adsorption rates that are, for example, comparable with those of phages infective in mesophilic conditions. Despite the small number of Shewanella phages characterized here, we could already find different types of phage-host interactions including a putative abortive infection.
Asunto(s)
Bacteriófagos/clasificación , Flavobacterium/virología , Cubierta de Hielo/virología , Shewanella/virología , Vibrio/virología , Bacteriófagos/genética , Bacteriófagos/aislamiento & purificación , Secuencia de Bases , ADN Bacteriano/genética , ADN Viral/genética , Genoma Viral/genética , Procesos Heterotróficos , Datos de Secuencia Molecular , Océanos y Mares , Análisis de Secuencia de ADNRESUMEN
In search for sea ice bacteria and their phages from the Baltic Sea ice, two ice samples were collected from land-fast ice in a south-west Finland coastal site in February and March 2011. Bacteria were isolated from the melted sea ice samples and phages were screened from the same samples for 43 purified isolates. Plaque-producing phages were found for 15 bacterial isolates at 3 °C. Ten phage isolates were successfully plaque purified and eight of them were chosen for particle purification to analyze their morphology and structural proteins. Phage 1/32 infecting an isolate affiliated to phylum Bacteroidetes (Flavobacterium sp.) is a siphovirus and six phages infecting isolates affiliated to γ-Proteobacteria (Shewanella sp.) hosts were myoviruses. Cross titrations between the hosts showed that all studied phages are host specific. Phage solutions, host growth and phage infection were tested in different temperatures revealing phage temperature tolerance up to 45 °C, whereas phage infection was in most of the cases retarded above 15 °C. This study is the first to report isolation and cultivation of ice bacteria and cold-active phages from the Baltic Sea ice.
Asunto(s)
Bacteriófagos/aislamiento & purificación , Flavobacterium/virología , Cubierta de Hielo/microbiología , Agua de Mar/microbiología , Shewanella/virología , Frío , Finlandia , Flavobacterium/aislamiento & purificación , Shewanella/aislamiento & purificaciónRESUMEN
Low-temperature ecosystems represent the largest biosphere on Earth, and yet our understanding of the roles of bacteriophages in these systems is limited. Here, the influence of the cold-active filamentous phage SW1 on the phenotype and gene transcription of its host, Shewanella piezotolerans WP3 (WP3), was investigated by construction of a phage-free strain (WP3ΔSW1), which was compared with the wild-type strain. The expression of 49 genes, including 16 lateral flagellar genes, was found to be significantly influenced by SW1 at 4°C, as demonstrated by comparative whole-genome microarray analysis. WP3ΔSW1 was shown to have a higher production of lateral flagella than WP3 and enhanced swarming motility when cultivated on solid agar plates. Besides, SW1 has a remarkable impact on the expression of a variety of host genes in liquid culture, particularly the genes related to the membrane and to the production of lateral flagella. These results suggest that the deep-sea bacterium WP3 might balance the high-energy demands of phage maintenance and swarming motility at low temperatures. The phage SW1 is shown to have a significant influence on the swarming ability of the host and thus may play an important role in adjusting the fitness of the cells in the deep-sea environment.
Asunto(s)
Frío , Flagelos/metabolismo , Inovirus/fisiología , Shewanella/genética , Genes Bacterianos , Procesamiento de Imagen Asistido por Computador , Inovirus/aislamiento & purificación , Microscopía Electrónica de Transmisión , Análisis de Secuencia por Matrices de Oligonucleótidos , ARN Bacteriano/genética , Shewanella/crecimiento & desarrollo , Shewanella/virologíaRESUMEN
Little is known about the response of deep-sea virus and their relationship with their host towards environmental change. Although viruses are thought to play key roles in the deep-sea ecological evolution and biogeochemical cycling, these roles are yet to be defined. This study aims to delineate the relationship between a deep-sea filamentous phage SW1 and its host Shewanella piezotolerans (S. piezotolerans) WP3, and their response towards temperature change. The copy number of SW1's replicative form (RF-) DNA and single-stranded (ss-) DNA along the different growth phases of WP3 were quantified at 20°C and 4°C, respectively. The copy number of SW1 RF-DNA was found to be temperature and growth phase-dependent, while the ssDNA of SW1 was only produced at 4°C. This is the first report showing low-temperature dependence of phage DNA replication. The transcription of SW1 key genes fpsA and fpsR were also found to be induced at low temperature during all the monitored growth periods of WP3. Additionally, the transcription of SW1 was found to be induced by cold-shock while its DNA replication was not changed. Our data demonstrates a dynamic change of virus DNA replication and transcription in accordance with host growth, and the low temperature adapted mechanisms for SW1 activities in the deep sea. This low temperature adapted deep-sea virus-bacterium system could serve as an ideal model to further study the mechanism and relationship of deep-sea virus-bacteria ecosystems.
Asunto(s)
Bacteriófagos/fisiología , Replicación del ADN/fisiología , ADN Viral/biosíntesis , Ecosistema , Evolución Molecular , Shewanella/virología , Transcripción Genética/fisiología , Replicación Viral/fisiología , Respuesta al Choque por Frío , ADN Viral/genética , Genes Virales/fisiología , Océanos y Mares , Proteínas Virales/biosíntesis , Proteínas Virales/genéticaRESUMEN
La alta frecuencia de diseminación de estos determinantes pone de manifiesto la capacidad de este género para actuar como reservorio y a su vez vector de la resistencia antibiótica
Asunto(s)
Farmacorresistencia Microbiana , Infección Hospitalaria , Shewanella/clasificación , Shewanella/metabolismo , Shewanella/virologíaRESUMEN
Shewanella oneidensis MR-1 is capable of forming highly structured surface-attached communities. By DNase I treatment, we demonstrated that extracellular DNA (eDNA) serves as a structural component in all stages of biofilm formation under static and hydrodynamic conditions. We determined whether eDNA is released through cell lysis mediated by the three prophages LambdaSo, MuSo1 and MuSo2 that are harbored in the genome of S. oneidensis MR-1. Mutant analyses and infection studies revealed that all three prophages may individually lead to cell lysis. However, only LambdaSo and MuSo2 form infectious phage particles. Phage release and cell lysis already occur during early stages of static incubation. A mutant devoid of the prophages was significantly less prone to lysis in pure culture. In addition, the phage-less mutant was severely impaired in biofilm formation through all stages of development, and three-dimensional growth occurred independently of eDNA as a structural component. Thus, we suggest that in S. oneidensis MR-1 prophage-mediated lysis results in the release of crucial biofilm-promoting factors, in particular eDNA.