Characterization of Bacteriophage cd2, a Siphophage Infecting Carnobacterium divergens and a Representative Species of a New Genus of Phage.

Carnobacterium divergens is frequently isolated from natural environments and is a predominant species found in refrigerated foods, particularly meat, seafood, and dairy. While there is substantial interest in using C. divergens as biopreservatives and/or probiotics, some strains are known to be fish pathogens, and the uncontrolled growth of C. divergens has been associated with food spoilage. Bacteriophages offer a selective approach to identify and control the growth of bacteria; however, to date, few phages targeting C. divergens have been reported. In this study, we characterize bacteriophage cd2, which we recently isolated from minced beef. A detailed host range study reveals that phage cd2 infects certain phylogenetic groups of C. divergens. This phage has a latent period of 60 min and a burst size of ~28 PFU/infected cell. The phage was found to be acid and heat sensitive, with a complete loss of phage activity when stored at pH 2 or heated to 60°C. Electron microscopy shows that phage cd2 is a siphophage, and while it shares the B3 morphotype with a unique cluster of Listeria and Enterococcus phages, a comparison of genomes reveals that phage cd2 comprises a new genus of phage, which we have termed as Carnodivirus. IMPORTANCE Currently, very little is known about phages that infect carnobacteria, an important genus of lactic acid bacteria with both beneficial and detrimental effects in the food and aquaculture industries. This report provides a detailed characterization of phage cd2, a novel siphophage that targets Carnobacterium divergens, and sets the groundwork for understanding the biology of these phages and their potential use in the detection and biocontrol of C. divergens isolates.

Habitat-linked genetic structure for white-crowned sparrow (Zonotrichia leucophrys): Local factors shape population genetic structure.

Ecological, environmental, and geographic factors all influence genetic structure. Species with broad distributions are ideal systems because they cover a range of ecological and environmental conditions allowing us to test which components predict genetic structure. This study presents a novel, broad geographic approach using molecular markers, morphology, and habitat modeling to investigate rangewide and local barriers causing contemporary genetic differentiation within the geographical range of three white-crowned sparrow (Zonotrichia leucophrys) subspecies: Z. l. gambelii, Z. l. oriantha, and Z. l. pugetensis. Three types of genetic markers showed geographic distance between sampling sites, elevation, and ecosystem type are key factors contributing to population genetic structure. Microsatellite markers revealed white-crowned sparrows do not group by subspecies, but instead indicated four groupings at a rangewide scale and two groupings based on coniferous and deciduous ecosystems at a local scale. Our analyses of morphological variation also revealed habitat differences; sparrows from deciduous ecosystems are larger than individuals from coniferous ecosystems based on principal component analyses. Habitat modeling showed isolation by distance was prevalent in describing genetic structure, but isolation by resistance also had a small but significant influence. Not only do these findings have implications concerning the accuracy of subspecies delineations, they also highlight the critical role of local factors such as habitat in shaping contemporary population genetic structure of species with high dispersal ability.

Genome Sequences of Bacteriophages cd2, cd3, and cd4, which Specifically Target Carnobacterium divergens.

Carnobacteria have been implicated in food spoilage, but also in protection against pathogenic bacteria. We report the isolation and complete genome sequences of three bacteriophages (phages cd2, cd3, and cd4) that specifically target Carnobacterium divergens. The genome sizes are approximately 57 kbp and have limited homology to known enterococcal and streptococcal phages.