Mobilisation and remobilisation of a large archetypal pathogenicity island of uropathogenic Escherichia coli in vitro support the role of conjugation for horizontal transfer of genomic islands

Background: A substantial amount of data has been accumulated supporting the important role of genomic islands (GEIs) - including pathogenicity islands (PAIs) - in bacterial genome plasticity and the evolution of bacterial pathogens. Their instability and the high level sequence similarity of different (partial) islands suggest an exchange of PAIs between strains of the same or even different bacterial species by horizontal gene transfer (HGT). Transfer events of archetypal large genomic islands of enterobacteria which often lack genes required for mobilisation or transfer have been rarely investigated so far. Results: To study mobilisation of such large genomic regions in prototypic uropathogenic E. coli (UPEC) strain 536, PAI II536 was supplemented with the mobRP4 region, an origin of replication (oriVR6K), an origin of transfer (oriTRP4) and a chloramphenicol resistance selection marker. In the presence of helper plasmid RP4, conjugative transfer of the 107-kb PAI II536 construct occured from strain 536 into an E. coli K-12 recipient. In transconjugants, PAI II536 existed either as a cytoplasmic circular intermediate (CI) or integrated site-specifically into the recipient’s chromosome at the leuX tRNA gene. This locus is the chromosomal integration site of PAI II536 in UPEC strain 536. From the E. coli K-12 recipient, the chromosomal PAI II536 construct as well as the CIs could be successfully remobilised and inserted into leuX in a PAI II536 deletion mutant of E. coli 536. Conclusions: Our results corroborate that mobilisation and conjugal transfer may contribute to evolution of bacterial pathogens through horizontal transfer of large chromosomal regions such as PAIs. Stabilisation of these mobile genetic elements in the bacterial chromosome result from selective loss of mobilisation and transfer functions of genomic islands

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Origin and evolution of hybrid Shiga toxin-producing and uropathogenic (STEC/UPEC) "Escherichia coli" of sequence type 141

Detailed parameters and E. coli O157:H7 Sakai genes that were finally used for BEAST analysi

Role of pathogenicity island-associated integrases in the genome plasticity of uropathogenic Escherichia coli strain 536

(T)he genome of uropathogenic Escherichia coli isolate 536 contains five well-characterized pathogenicity islands (PAIs) encoding key virulence factors of this strain. Except PAI IV536, the four other PAIs of strain 536 are flanked by direct repeats (DRs), carry intact integrase genes and are able to excise site-specifically from the chromosome. Genome screening of strain 536 identified a sixth putative asnW-associated PAI. Despite the presence of DRs and an intact integrase gene, excision of this island was not detected. To investigate the role of PAI-encoded integrases for the recombination process the int genes of each unstable island of strain 536 were inactivated. For PAI I-536 and PAI II536, their respective P4-like integrase was required for their excision. PAI III536 carries two integrase genes, intA, encoding an SfX-like integrase, and intB, coding for an integrase with weak similarity to P4-like integrases. Only intB was required for site-specific excision of this island. For PAI V-536, excision could not be abolished after deleting its P4-like integrase gene but additional deletion of the PAI II536-specific integrase gene was required. Therefore, although all mediated by P4-like integrases, the activity of the PAI excision machinery is most often restricted to its cognate island. This work also demonstrates for the first time the existence of a cross-talk between integrases of different PAIs and shows that this cross-talk is unidirectional

Käytännön kosteikkosuunnittelu

Maatalouden vesiensuojelua edistetään monin tavoin. Ravinteita ja eroosioainesta sisältäviä valumavesiä pyritään puhdistamaan erilaisissa kosteikoissa. Tämä opas on kirjoitettu avuksi pienimuotoisten kosteikkojen perustamiseen. Oppaassa esitetään käytännönläheisesti kosteikon toteuttamisen eri vaiheet paikan valinnasta suunnitteluun ja rakentamiseen. Vuonna 2010 julkaistun painoksen tiedot on saatettu ajantasalle. Julkaisu on toteutettu osana Tehoa maatalouden vesiensuojeluun (TEHO) -hanketta ja päivitetty TEHO Plus -hankkeen toimesta. Oppaan toivotaan lisäävän kiinnostusta kosteikkojen suunnitteluun ja edelleen niiden rakentamiseen

Plant Pest Newsletter PPST21, September 16, 1994

This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu