Effects of actin-like proteins encoded by two Bacillus pumilus phages on unstable lysogeny, revealed by genomic analysis

Characterization of vB_SalS_PSa2, a T5-like Demerecviridae bacteriophage, and its potential use in food matrices

This study characterizes a newly isolated Demerecviridae phage, named vB_SalS_PSa2, belonging to the phage T5 group. The main variations between vB_SalS_PSa2 and T5 concern structural proteins related to morphology and host recognition. vB_SalS_PSa2 is infective to 19 out of the 25 tested Salmonella enterica (including the rare "Sendai" and "Equine" serotypes) and Escherichia coli isolates, most of them being multidrug resistant. vB_SalS_PSa2 displayed good thermal stability (4-60 °C) and broad pH stability (4.0-12.0). It also exhibited antibacterial activity against S. enterica sv. Paratyphi A Enb50 at 4 °C in milk during the whole tested period (5 d), and for 3-6 h at both 25 and 37 °C. Furthermore, vB_SalS_PSa2 was able to inhibit biofilm formation and to show degradation activity on mature biofilms of E. coli K12 and S. enterica sv. Paratyphi Enb50 in both LB and milk. Altogether, these results indicate that phage vB_SalS_PSa2 is a valuable candidate for controlling foodborne S. enterica and E. coli pathogens.

Phage-driven coevolution reveals trade-off between antibiotic and phage resistance in Salmonella anatum

Phage therapy faces challenges against multidrug-resistant (MDR) Salmonella due to rapid phage-resistant mutant emergence. Understanding the intricate interplay between antibiotics and phages is essential for shaping Salmonella evolution and advancing phage therapy. In this study, MDR Salmonella anatum (S. anatum) 2089b coevolved with phage JNwz02 for 30 passages (60 days), then the effect of coevolution on the trade-off between phage and antibiotic resistance in bacteria was investigated. Our results demonstrated antagonistic coevolution between bacteria and phages, transitioning from arms race dynamics (ARD) to fluctuating selection dynamics (FSD). The fitness cost of phage resistance, manifested as reduced competitiveness, was observed. Bacteria evolved phage resistance while simultaneously regaining sensitivity to amoxicillin, ampicillin, and gentamicin, influenced by phage selection pressure and bacterial competitiveness. Moreover, the impact of phage selection pressure on the trade-off between antibiotic and phage resistance was more pronounced in the ARD stage than in the FSD stage. Whole genome analysis revealed mutations in the btuB gene in evolved S. anatum strains, with a notably higher mutation frequency in the ARD stage compared to the FSD stage. Subsequent knockout experiments confirmed BtuB as a receptor for phage JNwz02, and the deletion of btuB resulted in reduced bacterial competitiveness. Additionally, the mutations identified in the phage-resistant strains were linked to multiple single nucleotide polymorphisms (SNPs) associated with membrane components. This correlation implies a potential role of these SNPs in reinstating antibiotic susceptibility. These findings significantly advance our understanding of phage-host interactions and the impact of bacterial adaptations on antibiotic resistance.

A Genomic Analysis of the Bacillus Bacteriophage Kirovirus kirovense Kirov and Its Ability to Preserve Milk

Bacteriophages are widely recognized as alternatives to traditional antibiotics commonly used in the treatment of bacterial infection diseases and in the food industry, as phages offer a potential solution in combating multidrug-resistant bacterial pathogens. In this study, we describe a novel bacteriophage, Kirovirus kirovense Kirov, which infects members of the Bacillus cereus group. Kirovirus kirovense Kirov is a broad-host-range phage belonging to the Caudoviricetes class. Its chromosome is a linear 165,667 bp double-stranded DNA molecule that contains two short, direct terminal repeats, each 284 bp long. According to bioinformatics predictions, the genomic DNA contains 275 protein-coding genes and 5 tRNA genes. A comparative genomic analysis suggests that Kirovirus kirovense Kirov is a novel species within the Kirovirus genus, belonging to the Andregratiavirinae subfamily. Kirovirus kirovense Kirov demonstrates the ability to preserve and decontaminate B. cereus from cow milk when present in milk at a concentration of 104 PFU/mL. After 4 h of incubation with the phage, the bacterial titer drops from 105 to less than 102 CFU/mL.

Characterization of bacteriophage vB_KleM_KB2 possessing high control ability to pathogenic Klebsiella pneumoniae

Klebsiella pneumoniae is a widespread pathogen of several human diseases. The emergence of multidrug-resistant K. pneumoniae makes the treatment of these diseases a significant challenge. The application of bacteriophages is a potential approach for dealing with the emergence of multidrug-resistant pathogenic bacteria. This study isolates a novel bacteriophage vB_KleM_KB2 that infects the multidrug-resistant clinical isolates of K. pneumoniae. The bacteriophage exhibits a short latent period of 10 min, and can effectively lyse the bacterium within 60 min. Notably, the bacteriophage can completely inhibit the growth of the host bacterium at the initial concentration of 107 CFU/mL with a low multiplicity of infection of 0.001, which proves its high lytic activity. Furthermore, the bacteriophage shows high environmental tolerances, which can facilitate the practical application of the bacteriophage. Analysis of the bacteriophage genome shows that the bacteriophage possesses a novel genome sequence and can represent a new bacteriophage genus. Considering the high lytic activity, short latent period, high stability, and novel genetic background, bacteriophage vB_KleM_KB2 enriches the bacteriophage library and provides a new alternative for controlling the diseases caused by multidrug-resistant pathogenic K. pneumoniae.

Comparative genomic analyses reveal genetic characteristics and pathogenic factors of Bacillus pumilus HM-7

Bacillus pumilus plays an important role in industrial application and biocontrol activities, as well as causing humans and plants disease, leading to economic losses and biosafety concerns. However, until now, the pathogenesis and underlying mechanisms of B. pumilus strains remain unclear. In our previous study, one representative isolate of B. pumilus named HM-7 has been recovered and proved to be the causal agent of fruit rot on muskmelon (Cucumis melo). Herein, we present a complete and annotated genome sequence of HM-7 that contains 4,111 coding genes in a single 3,951,520 bp chromosome with 41.04% GC content. A total of 3,481 genes were functionally annotated with the GO, COG, and KEGG databases. Pan-core genome analysis of HM-7 and 20 representative B. pumilus strains, as well as six closely related Bacillus species, discovered 740 core genes and 15,205 genes in the pan-genome of 21 B. pumilus strains, in which 485 specific-genes were identified in HM-7 genome. The average nucleotide identity (ANI), and whole-genome-based phylogenetic analysis revealed that HM-7 was most closely related to the C4, GR8, MTCC-B6033, TUAT1 and SH-B11 strains, but evolutionarily distinct from other strains in B. pumilus. Collinearity analysis of the six similar B. pumilus strains showed high levels of synteny but also several divergent regions for each strains. In the HM-7 genome, we identified 484 genes in the carbohydrate-active enzymes (CAZyme) class, 650 genes encoding virulence factors, and 1,115 genes associated with pathogen-host interactions. Moreover, three HM-7-specific regions were determined, which contained 424 protein-coding genes. Further investigation of these genes showed that 19 pathogenesis-related genes were mainly associated with flagella formation and secretion of toxic products, which might be involved in the virulence of strain HM-7. Our results provided detailed genomic and taxonomic information for the HM-7 strain, and discovered its potential pathogenic mechanism, which lay a foundation for developing effective prevention and control strategies against this pathogen in the future.

Isolation, characterization, and application of a novel polyvalent lytic phage STWB21 against typhoidal and nontyphoidal Salmonella spp

Salmonella is one of the common causal agents of bacterial gastroenteritis-related morbidity and mortality among children below 5 years and the elderly populations. Salmonellosis in humans is caused mainly by consuming contaminated food originating from animals. The genus Salmonella has several serovars, and many of them are recently reported to be resistant to multiple drugs. Therefore, isolation of lytic Salmonella bacteriophages in search of bactericidal activity has received importance. In this study, a Salmonella phage STWB21 was isolated from a lake water sample and found to be a novel lytic phage with promising potential against the host bacteria Salmonella typhi. However, some polyvalence was observed in their broad host range. In addition to S. typhi, the phage STWB21 was able to infect S. paratyphi, S. typhimurium, S. enteritidis, and a few other bacterial species such as Sh. flexneri 2a, Sh. flexneri 3a, and ETEC. The newly isolated phage STWB21 belongs to the Siphoviridae family with an icosahedral head and a long flexible non-contractile tail. Phage STWB21 is relatively stable under a wide range of pH (4–11) and temperatures (4°C–50°C) for different Salmonella serovars. The latent period and burst size of phage STWB21 against S. typhi were 25 min and 161 plaque-forming units per cell. Since Salmonella is a foodborne pathogen, the phage STWB21 was applied to treat a 24 h biofilm formed in onion and milk under laboratory conditions. A significant reduction was observed in the bacterial population of S. typhi biofilm in both cases. Phage STWB21 contained a dsDNA of 112,834 bp in length, and the GC content was 40.37%. Also, genomic analysis confirmed the presence of lytic genes and the absence of any lysogeny or toxin genes. Overall, the present study reveals phage STWB21 has a promising ability to be used as a biocontrol agent of Salmonella spp. and proposes its application in food industries.

Morphological, biological, and genomic characterization of a newly isolated lytic phage Sfk20 infecting Shigella flexneri, Shigella sonnei, and Shigella dysenteriae1

Shigellosis, caused by Shigella bacterial spp., is one of the leading causes of diarrheal morbidity and mortality. An increasing prevalence of multidrug-resistant Shigella species has revived the importance of bacteriophages as an alternative therapy to antibiotics. In this study, a novel bacteriophage, Sfk20, has been isolated from water bodies of a diarrheal outbreak area in Kolkata (India) with lytic activity against many Shigella spp. Phage Sfk20 showed a latent period of 20 min and a large burst size of 123 pfu per infected cell in a one-step growth analysis. Phage-host interaction and lytic activity confirmed by phage attachment, intracellular phage development, and bacterial cell burst using ultrathin sectioning and TEM analysis. The genomic analysis revealed that the double-stranded DNA genome of Sfk20 contains 164,878 bp with 35.62% G + C content and 241 ORFs. Results suggested phage Sfk20 to include as a member of the T4 myoviridae bacteriophage group. Phage Sfk20 has shown anti-biofilm potential against Shigella species. The results of this study imply that Sfk20 has good possibilities to be used as a biocontrol agent.

Putative plasmid prophages of Bacillus cereus sensu lato may hold the key to undiscovered phage diversity

Bacteriophages are bacterial viruses and the most abundant biological entities on Earth. Temperate bacteriophages can form prophages stably maintained in the host population: they either integrate into the host genome or replicate as plasmids in the host cytoplasm. As shown, tailed temperate bacteriophages may form circular plasmid prophages in many bacterial species of the taxa Firmicutes, Gammaproteobacteria and Spirochaetes. The actual number of such prophages is thought to be underestimated for two main reasons: first, in bacterial whole genome-sequencing assemblies, they are difficult to distinguish from actual plasmids; second, there is an absence of experimental studies which are vital to confirm their existence. In Firmicutes, such prophages appear to be especially numerous. In the present study, we identified 23 genomes from species of the Bacillus cereus group that were deposited in GenBank as plasmids and may belong to plasmid prophages with little or no homology to known viruses. We consider these putative prophages worth experimental assays since it will broaden our knowledge of phage diversity and suggest that more attention be paid to such molecules in all bacterial sequencing projects as this will help in identifying previously unknown phages.

Bacillus-infecting bacteriophage Izhevsk harbors thermostable endolysin with broad range specificity

Several bacterial species belonging to the Bacillus cereus group are known to be causative agents of food poisoning and severe human diseases. Bacteriophages and their lytic enzymes called endolysins have been widely shown to provide for a supplemental or primary means of treating bacterial infections. In this work we present a new broad-host-range phage Izhevsk, which infects the members of the Bacillus cereus group. Transmission electron microscopy, genome sequencing and comparative analyses revealed that Izhevsk is a temperate phage with Siphoviridae morphology and belongs to the same genus as the previously described but taxonomically unclassified bacteriophages Tsamsa and Diildio. The Ply57 endolysin of Izhevsk phage has broad-spectrum activity against B. cereus sensu lato. The thermolability of Ply57 is higher than that of the PlyG of Wβ phage. This work contributes to our current understanding of phage biodiversity and may be useful for further development of efficient antimicrobials aimed at diagnosing and treating infectious diseases and food contaminations caused by the Bacillus cereus group of bacteria.

Isolation and Characterization of a Novel Phage for Controlling Multidrug-Resistant Klebsiella pneumoniae

The emergence of multidrug-resistant bacterial pathogens has severely threatened global health. A phage with the ability to efficiently and specifically lyse bacteria is considered an alternative for controlling multidrug-resistant bacterial pathogens. The discovery of novel agents for controlling the infections caused by K. pneumoniae is urgent due to the broad multidrug-resistance of K. pneumoniae. Only a few phage isolates have been reported to infect multidrug-resistant K. pneumoniae. In this study, by using the multidrug-resistant K. pneumoniae strain as an indicator, a novel phage called vB_KleS-HSE3, which maintains high antibacterial activity and high physical stability, was isolated from hospital sewage. This phage infected one of four tested multidrug-resistant K. pneumoniae strains. This phage belongs to the Siphoviridae family and a comparative genomic analysis showed that this phage is part of a novel phage lineage among the Siphoviridae family of phages that infect strains of Klebsiella. Based on its features, the vB_KleS-HSE3 phage has potential for controlling infections caused by multidrug-resistant K. pneumoniae.

Analysis of Spounaviruses as a Case Study for the Overdue Reclassification of Tailed Phages

Tailed bacteriophages are the most abundant and diverse viruses in the world, with genome sizes ranging from 10 kbp to over 500 kbp. Yet, due to historical reasons, all this diversity is confined to a single virus order—Caudovirales, composed of just four families: Myoviridae, Siphoviridae, Podoviridae, and the newly created Ackermannviridae family. In recent years, this morphology-based classification scheme has started to crumble under the constant flood of phage sequences, revealing that tailed phages are even more genetically diverse than once thought. This prompted us, the Bacterial and Archaeal Viruses Subcommittee of the International Committee on Taxonomy of Viruses (ICTV), to consider overall reorganization of phage taxonomy. In this study, we used a wide range of complementary methods—including comparative genomics, core genome analysis, and marker gene phylogenetics—to show that the group of Bacillus phage SPO1-related viruses previously classified into the Spounavirinae subfamily, is clearly distinct from other members of the family Myoviridae and its diversity deserves the rank of an autonomous family. Thus, we removed this group from the Myoviridae family and created the family Herelleviridae—a new taxon of the same rank. In the process of the taxon evaluation, we explored the feasibility of different demarcation criteria and critically evaluated the usefulness of our methods for phage classification. The convergence of results, drawing a consistent and comprehensive picture of a new family with associated subfamilies, regardless of method, demonstrates that the tools applied here are particularly useful in phage taxonomy. We are convinced that creation of this novel family is a crucial milestone toward much-needed reclassification in the Caudovirales order.

Bacillus Phage vB_BtS_B83 Previously Designated as a Plasmid May Represent a New Siphoviridae Genus

The Bacillus cereus group of bacteria includes, inter alia, the species known to be associated with human diseases and food poisoning. Here, we describe the Bacillus phage vB_BtS_B83 (abbreviated as B83) infecting the species of this group. Transmission electron microscopy (TEM) micrographs indicate that B83 belongs to the Siphoviridae family. B83 is a temperate phage using an arbitrium system for the regulation of the lysis–lysogeny switch, and is probably capable of forming a circular plasmid prophage. Comparative analysis shows that it has been previously sequenced, but was mistaken for a plasmid. B83 shares common genome organization and >46% of proteins with other the Bacillus phage, BMBtp14. Phylograms constructed using large terminase subunits and a pan-genome presence–absence matrix show that these phages form a clade distinct from the closest viruses. Based on the above, we propose the creation of a new genus named Bembunaquatrovirus that includes B83 and BMBtp14.

Phage Reduce Stability for Regaining Infectivity during Antagonistic Coevolution with Host Bacterium

The coevolution between phage and host bacterium is an important force that drives the evolution of the microbial community, yet the coevolution mechanisms have still not been well analyzed. Here, by analyzing the interaction between a Bacillus phage vB_BthS_BMBphi and its host bacterium, the coevolution mechanisms of the first-generation phage-resistant bacterial mutants and regained-infectivity phage mutants were studied. The phage-resistant bacterial mutants showed several conserved mutations as a potential reason for acquiring phage resistance, including the mutation in flagellum synthesis protein FlhA and cell wall polysaccharide synthesis protein DltC. All the phage-resistant bacterial mutants showed a deleted first transmembrane domain of the flagellum synthesis protein FlhA. Meanwhile, the regain-infectivity phage mutants all contained mutations in three baseplate-associated phage tail proteins by one nucleotide, respectively. A polymorphism analysis of the three mutant nucleotides in the wild-type phage revealed that the mutations existed before the interaction of the phage and the bacterium, while the wild-type phage could not infect the phage-resistant bacterial mutants, which might be because the synchronized mutations of the three nucleotides were essential for regaining infectivity. This study for the first time revealed that the synergism mutation of three phage baseplate-associated proteins were essential for the phages’ regained infectivity. Although the phage mutants regained infectivity, their storage stability was decreased and the infectivity against the phage-resistant bacterial mutants was reduced, suggesting the phage realized the continuation of the species by way of “dying to survive”.

Isolation of A Novel Bacillus thuringiensis Phage Representing A New Phage Lineage and Characterization of Its Endolysin

Phages, the parasites of bacteria, are considered as a new kind of antimicrobial agent due to their ability to lyse pathogenic bacteria. Due to the increase of available phage isolates, the newly isolated phage showed increasing genomic similarities with previously isolated phages. In this study, the novel phage vB_BthS_BMBphi, infecting the Bacillus thuringiensis strain BMB171, is isolated and characterized together with its endolysin. This phage is the first tadpole-like phage infecting the Bacillus strains. Genomic analysis shows that the phage genome is dissimilar to all those of previously characterized phages, only exhibiting low similarities with partial regions of the B. thuringiensis prophages. Phylogenetic analysis revealed that the phage was distant from the other Bacillus phages in terms of evolution. The novel genome sequence, the distant evolutionary relationship, and the special virion morphology together suggest that the phage vB_BthS_BMBphi could be classified as a new phage lineage. The genome of the phage is found to contain a restriction modification system, which might endow the phage with immunity to the restriction modification system of the host bacterium. The function of the endolysin PlyBMB encoded by the phage vB_BthS_BMBphi was analyzed, and the endolysin could lyse all the tested Bacillus cereus group strains, suggesting that the endolysin might be used in controlling pathogenic B. cereus group strains. The findings of this study enrich the understanding of phage diversity and provide a resource for controlling the B. cereus group pathogenic bacteria.

vB_LspM-01: a novel myovirus displaying pseudolysogeny in Lysinibacillus sphaericus C3-41

Lysinibacillus sphaericus has great application potential not only in the biocontrol of mosquitoes but also in the bioremediation of toxic metals. Phages contribute to the genetic diversity and niche adaptation of bacteria, playing essential roles in their life cycle, but may also cause economic damage for industrially important bacteria through phage contamination during fermentation. In this study, the L. sphaericus phage vB_LspM-01, which belongs to the Myoviridae family, was isolated and characterized. Results showed that vB_LspM-01 could specifically infect most tested L. sphaericus isolates but was not active against isolates belonging to other species. Furthermore, phage-born endolysin exhibited a broader antimicrobial spectrum than the host range of the phage. The vB_LspM-01 genome had no obvious similarity with that of its host, and ca. 22.6% of putative ORFs could not get a match with the public databases. Phylogenic analysis based on the putative terminase large subunit showed high similarity with the phages identified with pac-type headful packaging. The vB_LspM-01 encoding genes were only detected in a tiny percentage of L. sphaericus C3-41 individual cells in the wild population, whereas they showed much higher frequency in the resistant population grown within the plaques; however, the phage genes could not be stably inherited during host cell division. Additionally, the vB_LspM-01 encoding genes were only detected in the host population during the logarithmic growth phase. The mitomycin C induction helped the propagation and lysogeny-lysis switch of vB_LspM-01. The study demonstrated that vB_LspM-01 can be present in a pseudolysogenic state in L. sphaericus C3-41 populations.

Characterization of a novel phage infecting the pathogenic multidrug-resistant Bacillus cereus and functional analysis of its endolysin

Bacillus cereus is widely distributed food-borne pathogenic bacterium. Due to the harmness to human hearth and the generation of multidrug-resistant B. cereus, it is urgent to develop novel antimicrobial agents. Phage and phage endolysin were taken as novel antimicrobial substance for their specific lytic activity against pathogenic bacteria. In this study, a Myoviridae family phage, designated as vB_BceM-HSE3, infecting the pathogenic multidrug-resistant B. cereus strain was isolated and characterized along with its endolysin. Phage vB_BceM-HSE3 can specially infect the B. cereus group strains, including B. cereus, B. anthracis, and B. thuringiensis, and exhibits high temperature and pH tolerance, which endow it with high potential for been used in controlling pathogenic B. cereus group strains. Genomic analysis reveals that vB_BceM-HSE3 is a novel phage and only shows extremely low genome similarity with available phage genome. Functional analysis of endolysin PlyHSE3 encoding by vB_BceM-HSE3 shows that PlyHSE3 exhibits broader lytic spectrum than the phage and can lyse all the tested B. cereus group strains as well as the tested pathogenic strain of P. aeruginosa. PlyHSE3 also shows broad temperature and pH tolerance, and can efficiently lyse B. cereus strain at temperature at 4 °C and higher than 45 °C, which indicating that PlyHSE3 might can be used in controlling food-borne B. cereus during both the cold storage of food and the stage after the heat treatment of food. The findings of this study enrich our understanding of phage diversity as well as providing resources for developing phage therapy.

Characterization of a newly isolated phage infecting pathogenic Escherichia coli and analysis of its mosaic structural genes

The outbreak of multidrug-resistant pathogenic bacteria made the discovery of novel control strategies necessary. Phages have regained attention for their specific lytic activity against pathogenic bacterium. A newly isolated phage infecting the clinical Escherichia coli isolates, including several multidrug-resistant strains, was isolated, and this phage showed high control effects against the tested pathogenic E. coli strains. Host range analysis revealed that although the phage exhibited broad lytic spectrum against the tested E. coli strains, it could not lyse strains from the other species. Comparative genomic analysis showed that phages had undergone at least three genome recombination events during the evolutionary process at the position of the three phage tail genes, which was reported to be associated with the host range determination of the phage. The recombinant tail proteins contained functional domains that were highly similar with genes of the Salmonella phage and genes of Pseudomonas and Neisseria. The findings of this study not only provide resources for developing phage therapy against E. coli, but also showed the highly variable genome structure of the phage.

Prokaryotic cytoskeletons: protein filaments organizing small cells

Most, if not all, bacterial and archaeal cells contain at least one protein filament system. Although these filament systems in some cases form structures that are very similar to eukaryotic cytoskeletons, the term 'prokaryotic cytoskeletons' is used to refer to many different kinds of protein filaments. Cytoskeletons achieve their functions through polymerization of protein monomers and the resulting ability to access length scales larger than the size of the monomer. Prokaryotic cytoskeletons are involved in many fundamental aspects of prokaryotic cell biology and have important roles in cell shape determination, cell division and nonchromosomal DNA segregation. Some of the filament-forming proteins have been classified into a small number of conserved protein families, for example, the almost ubiquitous tubulin and actin superfamilies. To understand what makes filaments special and how the cytoskeletons they form enable cells to perform essential functions, the structure and function of cytoskeletal molecules and their filaments have been investigated in diverse bacteria and archaea. In this Review, we bring these data together to highlight the diverse ways that linear protein polymers can be used to organize other molecules and structures in bacteria and archaea.

Overview of the Diverse Roles of Bacterial and Archaeal Cytoskeletons

As discovered over the past 25 years, the cytoskeletons of bacteria and archaea are complex systems of proteins whose central components are dynamic cytomotive filaments. They perform roles in cell division, DNA partitioning, cell shape determination and the organisation of intracellular components. The protofilament structures and polymerisation activities of various actin-like, tubulin-like and ESCRT-like proteins of prokaryotes closely resemble their eukaryotic counterparts but show greater diversity. Their activities are modulated by a wide range of accessory proteins but these do not include homologues of the motor proteins that supplement filament dynamics to aid eukaryotic cell motility. Numerous other filamentous proteins, some related to eukaryotic IF-proteins/lamins and dynamins etc, seem to perform structural roles similar to those in eukaryotes.

Genomic analysis of Bacillus subtilis lytic bacteriophage ϕNIT1 capable of obstructing natto fermentation carrying genes for the capsule-lytic soluble enzymes poly-γ-glutamate hydrolase and levanase

Bacillus subtilis strains including the fermented soybean (natto) starter produce capsular polymers consisting of poly-γ-glutamate and levan. Capsular polymers may protect the cells from phage infection. However, bacteriophage ϕNIT1 carries a γ-PGA hydrolase gene (pghP) that help it to counteract the host cell's protection strategy. ϕNIT had a linear double stranded DNA genome of 155,631-bp with a terminal redundancy of 5,103-bp, containing a gene encoding an active levan hydrolase. These capsule-lytic enzyme genes were located in the possible foreign gene cluster regions between central core and terminal redundant regions, and were expressed at the late phase of the phage lytic cycle. All tested natto origin Spounavirinae phages carried both genes for capsule degrading enzymes similar to ϕNIT1. A comparative genomic analysis revealed the diversity among ϕNIT1 and Bacillus phages carrying pghP-like and levan-hydrolase genes, and provides novel understanding on the acquisition mechanism of these enzymatic genes.

Proteomic Analysis of a Novel Bacillus Jumbo Phage Revealing Glycoside Hydrolase As Structural Component

Tailed phages with genomes of larger than 200 kbp are classified as Jumbo phages and exhibited extremely high uncharted diversity. The genomic annotation of Jumbo phage is often disappointing because most of the predicted proteins, including structural proteins, failed to make good hits to the sequences in the databases. In this study, 23 proteins of a novel Bacillus Jumbo phage, vB_BpuM_BpSp, were identified as phage structural proteins by the structural proteome analysis, including 14 proteins of unknown function, 5 proteins with predicted function as structural proteins, a glycoside hydrolase, a Holliday junction resolvase, a RNA-polymerase β-subunit, and a host-coding portal protein, which might be hijacked from the host strain during phage virion assembly. The glycoside hydrolase (Gp255) was identified as phage virion component and was found to interact with the phage baseplate protein. Gp255 shows specific lytic activity against the phage host strain GR8 and has high temperature tolerance. In situ peptidoglycan-hydrolyzing activities analysis revealed that the expressed Gp255 and phage structural proteome exhibited glycoside hydrolysis activity against the tested GR8 cell extracts. This study identified the first functional individual structural glycoside hydrolase in phage virion. The presence of activated glycoside hydrolase in phage virions might facilitate the injection of the phage genome during infection by forming pores on the bacterial cell wall.

Genomic analysis of a ginger pathogen Bacillus pumilus providing the understanding to the pathogenesis and the novel control strategy

Bacillus pumilus has been widely identified as a pathogen of plant and human, while the genetic information is rarely available for pathogenic B. pumilus strains. B. pumilus GR8 is a pathogen that causes ginger rhizome rot disease by invading ginger rhizome parenchymatous tissues, growing in the extracellular space, and producing plant cell wall-degrading enzymes to destroy ginger cells. In this study, the genome of GR8 was sequenced and characterized. This genome was the third completely sequenced genome of the B. pumilus species, and it exhibited high similarity to the genome of the B. pumilus strain B6033. The genome of GR8 was 3.67 Mb in length and encoded 3,713 putative ORFs. Among these predicted proteins, numerous plant cell wall-degrading enzymes and several proteins associated with invading and adapting to the environment in the extracellular space of the ginger rhizome parenchymatous tissue were found. The GR8 genome contained only one restriction-modification system and no CRISPR/Cas system. The lack of phage-resistant system suggested that phages might be potential agents for the control of GR8. The genomic analysis of GR8 provided the understanding to the pathogenesis and the phage-control strategy of pathogenic B. pumilus strains.