No abstract

Xanthomonas arboricola pv. pruni is an important plant pathogen and the causal agent of bacterial spot of stone fruits ( Prunus spp). Here, we report a complete genome of X. arboricola pv. pruni strain Xcp1 generated from hybrid PacBio Sequel and Illumina NextSeq2000 sequencing.

A multiplex real-time isothermal amplification assay was developed using molecular beacons for the detection of Bacillus cereus and Staphylococcus aureus by targeting four important virulence genes. A correlation between targeting highly accessible DNA sequences and isothermal amplification based molecular beacon efficiency and sensitivity was demonstrated using phi(Φ)29 DNA polymerase at a constant isothermal temperature of 30°C. It was very selective and consistently detected down to 10 1 copies of DNA. The specificity and sensitivity of this assay, when tested with pure culture were high, surpassing those of currently used PCR assays for the detection of these organisms. The molecular beacon based real-time isothermal amplification (MBRTIA) assay could be carried out entirely in 96 well plates or well strips, enabling a rapid and high-throughput detection of food borne pathogens.

Previous studies have shown that IS and plasmids mediate HGT of symbiotic nodulation ( nod ) genes in soybean bradyrhizobia; however, these events require close cell-to-cell contact, which could be limited in soil environments. Bacteriophage-assisted gene transduction through spontaneously produced prophages provides a stable means of HGT not limited by the constraints of proximal cell-to-cell contact.

The ability to nodulate and fix atmospheric nitrogen in soybean root nodules makes soybean Bradyrhizobium spp. (SB) critical in supplying humanity’s nutritional needs. The intricacies of SB-plant interactions have been studied extensively; however, bradyrhizobial ecology as influenced by phages has received somewhat less attention even though these interactions may significantly impact soybean yield. In batch culture four SB strains, S06B (B. japonicum, S06B-Bj), S10J (B. japonicum, S10J-Bj), USDA 122 (B. diazoefficiens, USDA 122-Bd), and USDA 76T (B. elkanii, USDA 76-Be), spontaneously (without apparent exogenous chemical or physical induction) produced phages throughout the growth cycle; for three strains, phage concentrations exceeded cell numbers by ca. 3-fold after 48 h incubation. Observed spontaneously produced phages (SPP) were tailed. Phage terminase large-subunit protein phylogeny revealed possible differences in phage packaging and replication mechanisms. Bioinformatic analyses predicted multiple prophage regions within each SB genome preventing accurate identification of SPP genomes. A DNA sequencing approach was developed that accurately delineated the boundaries of four SPP genomes within three of the SB chromosomes. Read mapping suggested that the SPP are capable of transduction. In addition to the phages, bacterial strains S06B-Bj and USDA 76-Be were rich in mobile elements consisting of insertion sequences (IS) and large, conjugable, broad host range plasmids. The prevalence of SPP along with IS and plasmids indicate that horizontal gene transfer likely plays an outsized role in SB ecology and may subsequently impact soybean productivity.ImportancePrevious studies have shown that IS and plasmids mediate horizontal gene transfer (HGT) of symbiotic nodulation (nod) genes in SB; however, these events require close cell to cell contact which could be limited in soil environments. Bacteriophage assisted gene transduction through spontaneously produced prophages could provide stable means of HGT not limited by the constraints of proximal cell to cell contact. Phage mediated HGT events could be important in SB population ecology with concomitant impacts on soybean agriculture.