Characterization and comparative genomic analysis of a marine Bacillus phage reveal a novel viral genus.

Bacillus pumilus exhibits substantial economic significance, with its metabolism, adaptability, and ecological functions regulated by its bacteriophages. Here, we isolated and characterized a novel temperate phage vB_BpuM-ZY1 from B. pumilus derived from mangrove sediments by mitomycin C induction. Phage vB_BpuM-ZY1 is a typical myophage, which has an icosahedral head with a diameter of 43.34 ± 2.14 nm and a long contractible tail with a length of 238.58 ± 5.18 nm. Genomic analysis indicated that vB_BpuM-ZY1 encodes genes for lysogeny control, and its life cycle may be intricately regulated by multiple mechanisms. vB_BpuM-ZY1 was predicted to employ P2-like 5'-extended-cos packaging strategy. In addition, genome-wide phylogenetic tree and proteome tree analyses indicated that vB_BpuM-ZY1 belongs to the Peduoviridae family but forms a separate branch at a deeper taxonomic level. Particularly, the comparative genomic analysis showed that vB_BpuM-ZY1 has less than 70% intergenomic similarities with its most similar phages. Thus, we propose that vB_BpuM-ZY1 is a novel Bacillus phage belonging to a new genus under the Peduoviridae family. The protein-sharing network analysis identified 44 vB_BpuM-ZY1-related phages. Interestingly, these evolutionarily related myophages infect a broad range of hosts across different phyla, which may be explained by the high structural variations of the host recognition domain in their central spike proteins. Collectively, our study will contribute to our understanding of Bacillus phage diversity and Bacillus-phage interactions, as well as provide essential knowledge for the industrial application of B. pumilus. IMPORTANCE: Although recent metagenomics research has obtained a wealth of phage genetic information, much of it is considered "dark matter" because of the lack of similarity with known sequences in the database. Therefore, the isolation and characterization of novel phages will help to interpret the vast unknown viral metagenome data and improve our understanding of phage diversity and phage-host interactions. Bacillus pumilus shows high economic relevance due to its wide applications in biotechnology, industry, biopharma, and environmental sectors. Since phages influence the abundance, metabolism, evolution, fitness, and ecological functions of bacteria through complex interactions, the significance of isolation and characterization of novel phages infecting B. pumilus is apparent. In this study, we isolated and characterized a B. pumilus phage belonging to a novel viral genus, which provides essential knowledge for phage biology as well as the industrial application of B. pumilus.

Diversity and potential host-interactions of viruses inhabiting deep-sea seamount sediments.

Seamounts are globally distributed across the oceans and form one of the major oceanic biomes. Here, we utilized combined analyses of bulk metagenome and virome to study viral communities in seamount sediments in the western Pacific Ocean. Phylogenetic analyses and the protein-sharing network demonstrate extensive diversity and previously unknown viral clades. Inference of virus-host linkages uncovers extensive interactions between viruses and dominant prokaryote lineages, and suggests that viruses play significant roles in carbon, sulfur, and nitrogen cycling by compensating or augmenting host metabolisms. Moreover, temperate viruses are predicted to be prevalent in seamount sediments, which tend to carry auxiliary metabolic genes for host survivability. Intriguingly, the geographical features of seamounts likely compromise the connectivity of viral communities and thus contribute to the high divergence of viral genetic spaces and populations across seamounts. Altogether, these findings provides knowledge essential for understanding the biogeography and ecological roles of viruses in globally widespread seamounts.

Characterization and Comparative Genomic Analysis of a Deep-Sea Bacillus Phage Reveal a Novel Genus.

As the most abundant biological entities, viruses are the major players in marine ecosystems. However, our knowledge on virus diversity and virus-host interactions in the deep sea remains very limited. In this study, vB_BteM-A9Y, a novel bacteriophage infecting Bacillus tequilensis, was isolated from deep-sea sediments in the South China Sea. vB_BteM-A9Y has a hexametric head and a long, complex contractile tail, which are typical features of myophages. vB_BteM-A9Y initiated host lysis at 60 min post infection with a burst size of 75 PFU/cell. The phage genome comprises 38,634 base pairs and encodes 54 predicted open reading frames (ORFs), of which 27 ORFs can be functionally annotated by homology analysis. Interestingly, abundant ORFs involved in DNA damage repair were identified in the phage genome, suggesting that vB_BteM-A9Y encodes multiple pathways for DNA damage repair, which may help to maintain the stability of the host/phage genome. A BLASTn search of the whole genome sequence of vB_BteM-A9Y against the GenBank revealed no existing homolog. Consistently, a phylogenomic tree and proteome-based phylogenetic tree analysis showed that vB_BteM-A9Y formed a unique branch. Further comparative analysis of genomic nucleotide similarity and ORF homology of vB_BteM-A9Y with its mostly related phages showed that the intergenomic similarity between vB_BteM-A9Y and these phages was 0-33.2%. Collectively, based on the comprehensive morphological, phylogenetic, and comparative genomic analysis, we propose that vB_BteM-A9Y belongs to a novel genus under Caudoviricetes. Therefore, our study will increase our knowledge on deep-sea virus diversity and virus-host interactions, as well as expanding our knowledge on phage taxonomy.

Isolation, characterization, and comparative genomic analysis of vB_BviS-A10Y, a novel bacteriophage from mangrove sediments.

Mangrove is among the most carbon-rich biomes on earth, and viruses are believed to play a significant role in modulating local and global carbon cycling. However, few viruses have been isolated from mangrove sediments to date. Here, we report the isolation of a novel Bacillus phage (named phage vB_BviS-A10Y) from mangrove sediments. Phage vB_BviS-A10Y has a hexameric head with a diameter of ~ 79.22 nm and a tail with a length of ~ 548.56 nm, which are typical features of siphophages. vB_BviS-A10Y initiated host lysis at 3.5 h postinfection with a burst size of 25 plaque-forming units (PFU)/cell. The genome of phage vB_BviS-A10Y is 162,435 bp long with 225 predicted genes, and the GC content is 34.03%. A comparison of the whole genome sequence of phage vB_BviS-A10Y with those of other phages from the NCBI viral genome database showed that phage vB_BviS-A10Y has the highest similarity (73.7% identity with 33% coverage) to Bacillus phage PBC2. Interestingly, abundant auxiliary metabolic genes (AMGs) were identified in the vB_BviS-A10Y genome. The presence of a ß-1,3-glucosyltransferase gene in the phage genome supported our previous hypothesis that mangrove viruses may manipulate carbon cycling directly through their encoded carbohydrate-active enzyme (CAZyme) genes. Therefore, our study will contribute to a better understanding of the diversity and potential roles of viruses in mangrove ecosystems.

The Life Cycle Transitions of Temperate Phages: Regulating Factors and Potential Ecological Implications.

Phages are viruses that infect bacteria. They affect various microbe-mediated processes that drive biogeochemical cycling on a global scale. Their influence depends on whether the infection is lysogenic or lytic. Temperate phages have the potential to execute both infection types and thus frequently switch their infection modes in nature, potentially causing substantial impacts on the host-phage community and relevant biogeochemical cycling. Understanding the regulating factors and outcomes of temperate phage life cycle transition is thus fundamental for evaluating their ecological impacts. This review thus systematically summarizes the effects of various factors affecting temperate phage life cycle decisions in both culturable phage-host systems and natural environments. The review further elucidates the ecological implications of the life cycle transition of temperate phages with an emphasis on phage/host fitness, host-phage dynamics, microbe diversity and evolution, and biogeochemical cycles.