Comparative Genomic Analysis of Prophages in Human Vaginal Isolates of Streptococcus agalactiae.

Prophages, viral genomes integrated into bacterial genomes, are known to enhance bacterial colonization, adaptation, and ecological fitness, providing a better chance for pathogenic bacteria to disseminate and cause infection. Streptococcus agalactiae (Group B Streptococcus or GBS) is a common bacterium found colonizing the genitourinary tract of humans. However, GBS-colonized pregnant women are at risk of passing the organism to the neonate, where it can cause severe infections. GBS typically encode one or more prophages in their genomes, yet their role in pathogen fitness and virulence has not yet been described. Sequencing and bioinformatic analysis of the genomic content of GBS human isolates identified 42 complete prophages present in their genomes. Comparative genomic analyses of the prophage sequences revealed that the prophages could be classified into five distinct clusters based on their genomic content, indicating significant diversity in their genetic makeup. Prophage diversity was also identified across GBS capsule serotypes, sequence types (STs), and clonal clusters (CCs). Comprehensive genomic annotation revealed that all GBS strains encode paratox, a protein that prevents the uptake of DNA in Streptococcus, either on the chromosome, on the prophage, or both, and each prophage genome has at least one toxin-antitoxin system.

Genomic Characterization of the Cluster CZ4 Gordonia terrae Phage Oregano.

Oregano is a novel cluster CZ4 bacteriophage isolated from the soil using the bacterial host Gordonia terrae. The Oregano genome is 47,575 bp long and encodes two tyrosine integrases and a toxin/antitoxin system. It shares an immunity repressor with both Gordonia and Mycobacterium phages that spans 7 clusters.

Genome Sequence of the Cluster CD Gordonia Phage Widow.

Widow is a novel cluster CD bacteriophage isolated from a soil sample using the bacterial host Gordonia terrae. The Widow genome is 43,656 bp in length and encodes 64 protein-coding genes and no tRNAs. The genome shares 52 to 92% gene content with other cluster CD members.

Genome Sequence of Singleton Gordonia terrae Bacteriophage Finkle.

Bacteriophage Finkle is a temperate siphovirus isolated from soil on Gordonia terrae. The 47,895-bp genome has a GC content of 66.6% and encodes 84 protein-coding genes. The genome is not closely related to sequences in the Actinobacteriophage database, sharing less than 35% gene content, and was classified as a singleton.

Characterization of the cluster MabR prophages of Mycobacterium abscessus and Mycobacterium chelonae.

Mycobacterium abscessus is an emerging pathogen of concern in cystic fibrosis and immunocompromised patients and is considered one of the most drug-resistant mycobacteria. The majority of clinical Mycobacterium abscessus isolates carry 1 or more prophages that are hypothesized to contribute to virulence and bacterial fitness. The prophage McProf was identified in the genome of the Bergey strain of Mycobacterium chelonae and is distinct from previously described prophages of Mycobacterium abscessus. The McProf genome increases intrinsic antibiotic resistance of Mycobacterium chelonae and drives expression of the intrinsic antibiotic resistance gene, whiB7, when superinfected by a second phage. The prevalence of McProf-like genomes was determined in sequenced mycobacterial genomes. Related prophage genomes were identified in the genomes of 25 clinical isolates of Mycobacterium abscessus and assigned to the novel cluster, MabR. They share less than 10% gene content with previously described prophages; however, they share features typical of prophages, including polymorphic toxin-immunity systems.

Increased whiB7 expression and antibiotic resistance in Mycobacterium chelonae carrying two prophages.

BACKGROUND: The global rise in the incidence of non-tuberculosis mycobacterial infections is of increasing concern due their high levels of intrinsic antibiotic resistance. Although integrated viral genomes, called prophage, are linked to increased antibiotic resistance in some bacterial species, we know little of their role in mycobacterial drug resistance. RESULTS: We present here for the first time, evidence of increased antibiotic resistance and expression of intrinsic antibiotic resistance genes in a strain of Mycobacterium chelonae carrying prophage. Strains carrying the prophage McProf demonstrated increased resistance to amikacin. Resistance in these strains was further enhanced by exposure to sub-inhibitory concentrations of the antibiotic, acivicin, or by the presence of a second prophage, BPs. Increased expression of the virulence gene, whiB7, was observed in strains carrying both prophages, BPs and McProf, relative to strains carrying a single prophage or no prophages. CONCLUSIONS: This study provides evidence that prophage alter expression of important mycobacterial intrinsic antibiotic resistance genes and additionally offers insight into the role prophage may play in mycobacterial adaptation to stress.

Genomic diversity of bacteriophages infecting Microbacterium spp.

The bacteriophage population is vast, dynamic, old, and genetically diverse. The genomics of phages that infect bacterial hosts in the phylum Actinobacteria show them to not only be diverse but also pervasively mosaic, and replete with genes of unknown function. To further explore this broad group of bacteriophages, we describe here the isolation and genomic characterization of 116 phages that infect Microbacterium spp. Most of the phages are lytic, and can be grouped into twelve clusters according to their overall relatedness; seven of the phages are singletons with no close relatives. Genome sizes vary from 17.3 kbp to 97.7 kbp, and their G+C% content ranges from 51.4% to 71.4%, compared to ~67% for their Microbacterium hosts. The phages were isolated on five different Microbacterium species, but typically do not efficiently infect strains beyond the one on which they were isolated. These Microbacterium phages contain many novel features, including very large viral genes (13.5 kbp) and unusual fusions of structural proteins, including a fusion of VIP2 toxin and a MuF-like protein into a single gene. These phages and their genetic components such as integration systems, recombineering tools, and phage-mediated delivery systems, will be useful resources for advancing Microbacterium genetics.

Prophage-mediated defence against viral attack and viral counter-defence.

Temperate phages are common, and prophages are abundant residents of sequenced bacterial genomes. Mycobacteriophages are viruses that infect mycobacterial hosts including Mycobacterium tuberculosis and Mycobacterium smegmatis, encompass substantial genetic diversity and are commonly temperate. Characterization of ten Cluster N temperate mycobacteriophages revealed at least five distinct prophage-expressed viral defence systems that interfere with the infection of lytic and temperate phages that are either closely related (homotypic defence) or unrelated (heterotypic defence) to the prophage. Target specificity is unpredictable, ranging from a single target phage to one-third of those tested. The defence systems include a single-subunit restriction system, a heterotypic exclusion system and a predicted (p)ppGpp synthetase, which blocks lytic phage growth, promotes bacterial survival and enables efficient lysogeny. The predicted (p)ppGpp synthetase coded by the Phrann prophage defends against phage Tweety infection, but Tweety codes for a tetrapeptide repeat protein, gp54, which acts as a highly effective counter-defence system. Prophage-mediated viral defence offers an efficient mechanism for bacterial success in host-virus dynamics, and counter-defence promotes phage co-evolution.

Comparative genomics of Cluster O mycobacteriophages.

Mycobacteriophages--viruses of mycobacterial hosts--are genetically diverse but morphologically are all classified in the Caudovirales with double-stranded DNA and tails. We describe here a group of five closely related mycobacteriophages--Corndog, Catdawg, Dylan, Firecracker, and YungJamal--designated as Cluster O with long flexible tails but with unusual prolate capsids. Proteomic analysis of phage Corndog particles, Catdawg particles, and Corndog-infected cells confirms expression of half of the predicted gene products and indicates a non-canonical mechanism for translation of the Corndog tape measure protein. Bioinformatic analysis identifies 8-9 strongly predicted SigA promoters and all five Cluster O genomes contain more than 30 copies of a 17 bp repeat sequence with dyad symmetry located throughout the genomes. Comparison of the Cluster O phages provides insights into phage genome evolution including the processes of gene flux by horizontal genetic exchange.

Experimental transmission of infectious pancreatic necrosis virus from the blue mussel, Mytilus edulis, to cohabitating Atlantic Salmon (Salmo salar) smolts.

Integrated multitrophic aquaculture (IMTA) reduces the environmental impacts of commercial aquaculture systems by combining the cultivation of fed species with extractive species. Shellfish play a critical role in IMTA systems by filter-feeding particulate-bound organic nutrients. As bioaccumulating organisms, shellfish may also increase disease risk on farms by serving as reservoirs for important finfish pathogens such as infectious pancreatic necrosis virus (IPNV). The ability of the blue mussel (Mytilus edulis) to bioaccumulate and transmit IPNV to naive Atlantic salmon (Salmo salar) smolts was investigated. To determine the ability of mussels to filter and accumulate viable IPNV, mussels were held in water containing log 4.6 50% tissue culture infective dose(s) (TCID50) of the West Buxton strain of IPNV ml(-1). Viable IPNV was detected in the digestive glands (DGs) of IPNV-exposed mussels as early as 2 h postexposure. The viral load in mussel DG tissue significantly increased with time and reached log 5.35 ± 0.25 TCID50 g of DG tissue(-1) after 120 h of exposure. IPNV titers never reached levels that were significantly greater than that in the water. Viable IPNV was detected in mussel feces out to 7 days postdepuration, and the virus persisted in DG tissues for at least 18 days of depuration. To determine whether IPNV can be transmitted from mussels to Atlantic salmon, IPNV-exposed mussels were cohabitated with naive Atlantic salmon smolts. Transmission of IPNV did occur from mussels to smolts at a low frequency. The results demonstrate that a nonenveloped virus, such as IPNV, can accumulate in mussels and be transferred to naive fish.