Bacteriophage genomes rapidly evolve via mutation and horizontal gene transfer to counter evolving bacterial host defenses; such arms race dynamics should lead to divergence between phages from similar, geographically isolated ecosystems. However, near-identical phage genomes can reoccur over large geographical distances and several years apart, conversely suggesting many are stably maintained. Here, we show that phages with nearidentical core genomes in distant, discrete aquatic ecosystems maintain diversity by possession of numerous flexible gene modules, where homologous genes present in the pangenome interchange to create new phage variants. By repeatedly reconstructing the core and flexible regions of phage genomes from different metagenomes, we show a pool of homologous gene variants co-exist for each module in each location, however, the dominant variant shuffles independently in each module. These results suggest that in a natural community, recombination is the largest contributor to phage diversity, allowing a variety of host recognition receptors and genes to counter bacterial defenses to co-exist for each phage.

Bacterial ice nucleation activity (INA+ phenotype) can be traced to the product of a single gene, ina. A remarkably sparse distribution of this phenotype within three bacterial genera indicates that the ina gene may have followed an unusual evolutionary path. Southern blot analyses, coupled with assays for ice-nucleating ability, revealed that within four bacterial species an ina gene is present in some strains but absent from others. Results of hybridization experiments using DNA fragments that flank the ina gene suggested that the genotypic dimorphism of ina may be anomalous. A phylogenetic analysis of 16s ribosomal RNA gene sequences from a total of 14 ina+ and inabacterial strains indicated that the ina+ bacteria are not monophyletic but instead phylogenetically interspersed among ina-bacteria. The relationships of ina+ bacteria inferred from ina sequence did not coincide with those inferred from the 16s data. These results suggest the possibility of horizontal transfer in the evolution of bacterial ina genes.

Freshwater quality detection is important for pollution control. Three important components of water quality are pH, ammonia and dissolved HS and there is an urgent need for a high-precision sensor for simultaneous and continuous measurement. In this study, all-solid-state electrodes of Eh, pH, NH and S were manufactured and mounted to a wireless chemical sensor with multiple parameters. Calibration indicated that the pH electrode had a Nernst response with slope of 53.174 mV; the NH electrode had a detection limit of 10 mol/L (Nernst response slope of 53.56 mV between 10 to 10 mol/L). Ag/AgS has a detection limit of 10 mol/L (Nernst response slope of 28.439 mV). The sensor was cylindrical and small with low power consumption and low storage demand to achieve continuous in-situ monitoring for long periods. The sensor was tested for 10 days in streams at Trawsgoed Dairy farm in Aberystwyth, UK. At the intensively farmed Trawsgoed, the concentration of NH in the stream rose sharply after the application of slurry to adjacent fields. Further, the stream was overhung with extensive vegetation and exhibited changes in pH, which correlated with photosynthetic activity. Measurements of S were stable throughout the week. Our data demonstrate the applicability of our multiple electrode sensor.