The B. mycoides N host-virus system. I. Differences in appearance and "rate of growth" of the lysogenic and parent indicator strains

Characterization of φEf-vB1 prophage infecting oral Enterococcus faecalis and enhancing bacterial biofilm formation

Introduction. Enterococcus faecalis is a facultative, anaerobic, opportunistic pathogen associated with medical and dental diseases. Bacterial phenotypic traits and pathogenesis are often influenced by lysogeny.Aim. The aim of this study was to characterize both the morphology and complete genome sequences of induced prophages purified from E. faecalis clinical isolates.Methodology. E. faecalis isolates were recovered from the roots of teeth of patients attending an endodontic clinic. The morphological features of isolated phage were characterized using transmission electron microscopy (TEM). DNA sequencing was performed using the Illumina MiSeq platform.Results. TEM indicated that the isolated φEf-vB1 prophage belongs to the family Siphoviridae. The φEf-vB1 prophage was stable over a wide range of temperatures and pH. Sequencing of φEf-vB1 DNA revealed that the phage genome is 37 561 bp in length with a G+C content of 37.6mol% and contained 53 ORFs. Comparison with previously predicted prophage genomes using blast revealed that φEf-vB1 has a high sequence similarity to previously characterized phage genomes. The lysogenic E. faecalis strain exhibited a higher biofilm formation capacity relative to the non-lysogenic strain.Conclusion. The current findings highlight the role of lysogeny in modification of E. faecalis properties and reveal the potential importance of prophages in E. faecalis biology and pathogenesis.

Phages preying on Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis: past, present and future

Many bacteriophages (phages) have been widely studied due to their major role in virulence evolution of bacterial pathogens. However, less attention has been paid to phages preying on bacteria from the Bacillus cereus group and their contribution to the bacterial genetic pool has been disregarded. Therefore, this review brings together the main information for the B. cereus group phages, from their discovery to their modern biotechnological applications. A special focus is given to phages infecting Bacillus anthracis, B. cereus and Bacillus thuringiensis. These phages belong to the Myoviridae, Siphoviridae, Podoviridae and Tectiviridae families. For the sake of clarity, several phage categories have been made according to significant characteristics such as lifestyles and lysogenic states. The main categories comprise the transducing phages, phages with a chromosomal or plasmidial prophage state, γ-like phages and jumbo-phages. The current genomic characterization of some of these phages is also addressed throughout this work and some promising applications are discussed here.

Characteristics of a new vibrio-bacteriophage system

A vibrio-bacteriophage system isolated from San Francisco Bay mud is described. The vibrio lyses readily in distilled water and appears to be a new species. In contact with the phage it becomes lysogenic and forms large clumps. The phage presents no unique features.

The B mycoides N host-virus system. II. Interrelation of phage growth, bacterial multiplication, and lysis in infections of the indicator strain of B. mycoides N with phage N in nutrient broth

In nutrient broth at 30 to 32 degrees C., the cycle of virus growth (following adsorption) in lag phase cells of B. mycoides N included a period of intracellular multiplication, ranging from 0.8 to 1.3 hours, succeeded by a sharp rise in the free phage titer and then by a slower rise or a plateau in the extracellular phage content. The yield of virus per infected cell at 30 degrees C., as determined by a modified Burnet dilution technique, was about 76 plaque-forming particles. During the latent period, multiply infected cells showed no change in numbers. Coinciding with phage release, incomplete clearing occurred. The unlysed, remaining cells multiplied and the turbidity rose again. These survivors and their progeny were lysogenic.

The B. mycoides N host-virus system. III. Release of phage from the lysogenic strain

Experiments were performed to determine the mechanism of release of phage from the lysogenic strain of B. mycoides N. The results suggest that qualitatively the same situation obtains as in the phage-carrying cultures of B. megatherium 899 and E. coli Li; i.e., the population consists of two kinds of cells: "lysogènes potentiels" and "producteurs." Quantitatively, however, there are more "producers" in a broth culture of the lysogenic B. mycoides N, at least curing the first 4 to 8 hours after cells have been suspended in fresh medium, suggesting that the interaction between host and parasite is one in which the balance is easily swung in favor of the virus. These conclusions are based upon the following lines of evidence: (1) the slow "growth rate" of the lysogenic culture, (2) the fact that the colony count falls far below the plaque count or the filament count (which correspond) for a well washed suspension, (3) the increase in phage output in a large number of tubes, each containing a small number of lysogenic cells, after a few hours' incubation in nutrient broth at 30 degrees C.