Practicalities of Using Non-Local or Non-Recent Multilocus Sequence Typing Data for Source Attribution in Space and Time of Human Campylobacteriosis

In this study, 1208 Campylobacter jejuni and C. coli isolates from humans and 400 isolates from chicken, collected in two separate periods over 12 years in The Netherlands, were typed using multilocus sequence typing (MLST). Statistical evidence was found for a shift of ST frequencies in human isolates over time. The human MLST data were also compared to published data from other countries to determine geographical variation. Because only MLST typed data from chicken, taken from the same time point and spatial location, were available in addition to the human data, MLST datasets for other Campylobacter reservoirs from selected countries were used. The selection was based on the degree of similarity of the human isolates between countries. The main aim of this study was to better understand the consequences of using non-local or non-recent MLST data for attributing domestically acquired human Campylobacter infections to specific sources of origin when applying the asymmetric island model for source attribution. In addition, a power-analysis was done to find the minimum number of source isolates needed to perform source attribution using an asymmetric island model. This study showed that using source data from other countries can have a significant biasing effect on the attribution results so it is important to carefully select data if the available local data lack in quality and/or quantity. Methods aimed at reducing this bias were proposed.     

Rapid Growth Responses of Dark-Grown Wheat Seedlings to Red Light-Irradiation: I. Kinetic Studies on the Short-Term Growth Responses of Intact Coleoptiles at Different Seedling Age

Continuous recordings of the effect of red light on intact darkgrown wheat seedlings (Triticum aestivum L. cv. Hatri) weremade at different times after sowing. When the coleoptile tipregion was irradiated 50, 70 or 90 h after sowing with red lightfrom two opposite fibre bundles a decrease in extension ratewas detectable after a latent period of 10 to 15 min. Growthrate reached a fluence dependent minimum at about 60 min, afterwhich growth acceleration towards the dark control rate wasobserved. When continuous red irradiation was started 50 or70 h after sowing the dark control rate was reached 2.5 h afteronset of irradiation and growth rate was little above this levelduring the next 2 h. With older coleoptiles (90 h after sowing)the growth rate recovery was only up to 50% of the dark controlrate and a second phase in growth inhibition became detectableabout 2.5 h after onset of red exposure, characterized by acontinuous decrease in extension rate. Under R/FR pulse irradiationboth the red-light-induced transient growth inhibition and thesecond phase of growth inhibition exhibit far-red reversibilityup to the level of far-red induced growth rate changes. (Received September 19, 1986; Accepted December 8, 1986)     

Evolution of Red Algal Plastid Genomes: Ancient Architectures,Introns, Horizontal Gene Transfer,and Taxonomic Utility of Plastid Markers

Red algae have the most gene-rich plastid genomes known, but despite their evolutionary importance these genomes remain poorly sampled. Here we characterize three complete and one partial plastid genome from a diverse range of florideophytes. By unifying annotations across all available red algal plastid genomes we show they all share a highly compact and slowly-evolving architecture and uniquely rich gene complements. Both chromosome structure and gene content have changed very little during red algal diversification, and suggest that plastid-to nucleus gene transfers have been rare. Despite their ancient character, however, the red algal plastids also contain several unprecedented features, including a group II intron in a tRNA-Met gene that encodes the first example of red algal plastid intron maturase – a feature uniquely shared among florideophytes. We also identify a rare case of a horizontally-acquired proteobacterial operon, and propose this operon may have been recruited for plastid function and potentially replaced a nucleus-encoded plastid-targeted paralogue. Plastid genome phylogenies yield a fully resolved tree and suggest that plastid DNA is a useful tool for resolving red algal relationships. Lastly, we estimate the evolutionary rates among more than 200 plastid genes, and assess their usefulness for species and subspecies taxonomy by comparison to well-established barcoding markers such as cox1 and rbcL. Overall, these data demonstrates that red algal plastid genomes are easily obtainable using high-throughput sequencing of total genomic DNA, interesting from evolutionary perspectives, and promising in resolving red algal relationships at evolutionarily-deep and species/subspecies levels.