Complete genome sequences of three isolates of Xanthomonas fragariae, the bacterium responsible for angular leaf spots on strawberry plants

Xanthomonas fragariae is a worldwide spread plant bacterial disease causing angular leaf spots, and thus reducing the yield of production for strawberry fruits. Three isolates with variable geographic and time origins were sequenced with long-read technology (PacBio) to generate finished genomes of virulent strains and observe their variability in content

Genome-based population structure analysis of the strawberry plant pathogen Xanthomonas fragariae reveals two distinct groups that evolved independently before its species description

Xanthomonas fragariae is a quarantine organism in Europe, causing angular leaf spots on strawberry plants. It is spreading worldwide in strawberry-producing regions due to import of plant material through trade and human activities. In order to resolve the population structure at the strain level, we have employed high-resolution molecular typing tools on a comprehensive strain collection representing global and temporal distribution of the pathogen. Clustered regularly interspaced short palindromic repeat regions (CRISPRs) and variable number of tandem repeats (VNTRs) were identified within the reference genome of X. fragariae LMG 25863 as a potential source of variation. Strains from our collection were whole-genome sequenced and used in order to identify variable spacers and repeats for discriminative purpose. CRISPR spacer analysis and multiple-locus VNTR analysis (MLVA) displayed a congruent population structure, in which two major groups and a total of four subgroups were revealed. The two main groups were genetically separated before the first X. fragariae isolate was described and are potentially responsible for the worldwide expansion of the bacterial disease. Three primer sets were designed for discriminating CRISPR-associated markers in order to streamline group determination of novel isolates. Overall, this study describes typing methods to discriminate strains and monitor the pathogen population structure, more especially in the view of a new outbreak of the pathogen

Thin-film magnetic head and method of manufacturing the magnetic head

Thin-film magnetic head having a head face (103) and comprising a magnetoresistive element (109) oriented transversely to the head face and a flux-guiding element (107) of a magnetically permeable material terminating in the head face. A peripheral area (109a) of the magnetoresistive element extending parallel to the head face is present opposite the flux-guiding element for forming a magnetic connection between the magnetoresistive element and the flux-guiding element. The flux-guiding element and the peripheral area of the magnetoresistive element constitute a common magnetic contact face (111), while the magnetically permeable material of the flux-guiding element is electrically insulating

Magneto-optical recording medium

A magneto optical recording medium (2) comprising a substrate (4) and a recording layer (6), the recording layer (6) comprising a bilayer structure consisting of a first layer (8) on which a magnetic second layer (10) is deposited, the second layer (10) demonstrating perpendicular magnetic anisotropy and a saturation remanence of at least 90 %, whereby the magnetic material of the second layer (10) comprises an oxide of iron, and the first layer (8) comprises an oxidic material whose in-plane lattice parameter differs from that of the magnetic material, the growth of the second layer (10) upon the first layer (8) being at least locally epitaxial

Isolation of Salmonella enterica in seropositive classified finishing pig herds

The aim of this study was to assess the probability of detecting Salmonella from pen faecal samples in seropositive classified finishing pig herds. The study involved 77 herds from Denmark (20), the Netherlands (20), Greece (17) and Germany (20). The serological herd status was determined by the blood- sampling of 50 finishing pigs. Bacteriological sampling was performed by 20 pen faecal samples per herd. Over-all, 47 % of the blood samples had an OD% larger than 10 and 23 % larger than 40. Salmonella was isolated from 135 (9.3 %) pen faecal samples in 32 herds (42 %). Twenty-eight of these herds (87.5 %) had a within-herd seroprevalence larger than 50% at sample cut-off OD%\u3e10. A correlation coefficient of 0.62 was found between the proportion of culture positive- and seropositive samples in a herd at cut-off OD % \u3e 10 and of 0.58 at cut-off OD % \u3e 40. Due to the low sensitivity of culture methods, apparent ‘false positive’ serological results may well represent real infections not detected by bacteriological testing. In this study, there was an increasing probability of recovering Salmonella with increasing within-herd seroprevalence

Removal of bacterial plant pathogens in columns filled with quartz and natural sediments under anoxic and oxygenated conditions

Irrigation with surface water carrying plant pathogens poses a risk for agriculture. Managed aquifer recharge enhances fresh water availability while simultaneously it may reduce the risk of plant diseases by removal of pathogens during aquifer passage. We compared the transport of three plant pathogenic bacteria with Escherichia coli WR1 as reference strain in saturated laboratory column experiments filled with quartz sand, or sandy aquifer sediments. E. coli showed the highest removal, followed by Pectobacterium carotovorum, Dickeya solani and Ralstonia solanacearum. Bacterial and non-reactive tracer breakthrough curves were fitted with Hydrus-1D and compared with colloid filtration theory (CFT). Bacterial attachment to fine and medium aquifer sand under anoxic conditions was highest with attachment rates of max. katt1 = 765 day-1 and 355 day-1, respectively. Attachment was the least to quartz sand under oxic conditions (katt1 = 61 day-1). In CFT, sticking efficiencies were higher in aquifer than in quartz sand but there was no differentiation between fine and medium aquifer sand. Overall removal ranged between < 6.8 log10 m−1 in quartz and up to 40 log10 m−1 in fine aquifer sand. Oxygenation of the anoxic aquifer sediments for two weeks with oxic influent water decreased the removal. The results highlight the potential of natural sand filtration to sufficiently remove plant pathogenic bacteria during aquifer storage