Search

Due to the continuous use of copper containing bactericides without effective alternative bactericides, copper resistance has become more prevalent in plant pathogens, including Xanthomonas euvesicatoria pv. perforons (formerly Xanthomonas perforons), a predominant cause of bacterial leaf spot disease of tomato and pepper in the Southeastern United States. Previously, reports of copper resistance have been associated with a large conjugative plasmid. However, we have characterized a copper resistance genomic island located within the chromosome of multiple X. euvesicatoria pv. perforons strains. The island is distinct from a previously described chromosomally encoded copper resistance island in X. vesicatoria strain XVP26. Computational analysis revealed the genomic island to contain multiple genes associated with genetic mobility, including both phage-related genes and transposase. Among copper-tolerant strains of X. euvesicatoria pv. perforons isolated from Florida, the majority of strains were found to have the copper resistance chromosomally encoded rather than plasmid borne. Our results suggest that this copper resistance island may have two modes of horizontal gene transfer and that chromosomally encoded copper resistance genes may provide a fitness advantage over plasmid-borne resistance. [ABSTRACT FROM AUTHOR]

Bacteriophages or phages are viruses that infect bacterial cells (for the scope of this review we will also consider viruses that infect Archaea). The constant threat of phage infection is a major force that shapes evolution of microbial genomes. To withstand infection, bacteria had evolved numerous strategies to avoid recognition by phages or to directly interfere with phage propagation inside the cell. Classical molecular biology and genetic engineering had been deeply intertwined with the study of phages and host defenses. Nowadays, owing to the rise of phage therapy, broad application of CRISPR-Cas technologies, and development of bioinformatics approaches that facilitate discovery of new systems, phage biology experiences a revival. This review describes variety of strategies employed by microbes to counter phage infection. In the first part defense associated with cell surface, roles of small molecules, and innate immunity systems relying on DNA modification were discussed. The second part focuses on adaptive immunity systems, abortive infection mechanisms, defenses associated with mobile genetic elements, and novel systems discovered in recent years through metagenomic mining. [ABSTRACT FROM AUTHOR]

Background A successful implant reconstruction with optimal esthetics consists of a visually pleasing prosthesis and complete and healthy surrounding soft tissue. In the current literature, numerous indices used to qualitatively assess esthetics have been described. However, studies comparing the indices and their reproducibility are scarce. Purpose The aim of this study was to compare three different esthetic indices for the evaluation of single implant-supported crowns. Materials and Methods A total of 10 prosthodontists ( P), 10 orthodontists ( O), 10 general dentists ( G), and 10 lay people ( L) independently performed the same assessment using 30 photographs and corresponding casts with three different esthetic indices ( Peri-Implant and Crown Index [ PICI], Implant Crown Aesthetic Index [ ICAI], 'Pink Esthetic Score/White Esthetic Score [ PES/WES]) and repeated the evaluations 4 weeks later. Results The PES/WES and the PICI showed significantly higher esthetic scores (pink, white, total) and clinical acceptance compared with the ICAI in all four groups and in both assessments. The highest intraobserver agreement was achieved using the PES/WES and the least with the ICAI. The mean Kappa per group ranged from 0.18 (group L with ICAI) to 0.63 (group G with PICI). Conclusion In comparison with the ICAI, the PES/WES and PICI were more reproducible. Therefore, PES/WES and PICI seem to be more suitable as esthetic indices for single implant crowns. [ABSTRACT FROM AUTHOR]

Bacteria encode sophisticated anti-phage systems that are diverse and versatile and display high genetic mobility. How this variability and mobility occurs remains largely unknown. Here, we demonstrate that a widespread family of pathogenicity islands, the phage-inducible chromosomal islands (PICIs), carry an impressive arsenal of defense mechanisms, which can be disseminated intra- and inter-generically by helper phages. These defense systems provide broad immunity, blocking not only phage reproduction, but also plasmid and non-cognate PICI transfer. Our results demonstrate that phages can mobilize PICI-encoded immunity systems to use them against other mobile genetic elements, which compete with the phages for the same bacterial hosts. Therefore, despite the cost, mobilization of PICIs may be beneficial for phages, PICIs, and bacteria in nature. Our results suggest that PICIs are important players controlling horizontal gene transfer and that PICIs and phages establish mutualistic interactions that drive bacterial ecology and evolution. [Display omitted] • PICIs carry an impressive arsenal of defense systems • PICI-encoded defense systems confer resistance to various mobile genetic elements • These defense systems block horizontal gene transfer • Phages benefit from mobilizing PICIs to target competing mobile genetic elements Phage-inducible chromosomal islands (PICIs) are highly mobile genetic elements that not only provide a diversity of defense systems in gram-positive and gram-negative bacteria, but can also be induced by a helper phage to protect that helper phage and the bacterial host from competing phages and other mobile genetic elements. This reveals a complex mutualistic relationship between bacteria, PICIs, and their helper phages that may broadly affect horizontal gene transfer. [ABSTRACT FROM AUTHOR]

Methodology for time-weighted average (TWA) air measurements of semivolatile organophosphate triesters, widely used flame-retardants and plasticizers, and common indoor pollutants is presented. Dynamic non-equilibrium solid-phase microextraction (SPME) for air sampling, in combination with GC/PICI and ion trap tandem MS, yields a fast, almost solvent-free method with low detection limits. Methanol was used as reagent gas for PICI, yielding stable protonated molecules and few fragments. A field sampler, in which a pumped airflow over three polydimethylsiloxane (PDMS) 100-μm fibers in series was applied, was constructed, evaluated, and used for the measurements. The method LODs were in the range 2–26 ng m−3 for a sampling period of 2 h. The uptake on the SPME fibers was shown to be about five times faster for triphenyl phosphate compared to the other investigated organophosphate esters, most likely due to more lipophilic properties of the aromatic compound. The boundary layer for triphenyl phosphate when using a 100-µm PDMS sorbent was determined to 0.08 mm at a linear air velocity of 34 cm s−1. Five different organophosphate triesters were detected in air from a laboratory and a lecture hall, at concentrations ranging from 7 ng m−3 up to 2.8 μg m−3. [ABSTRACT FROM AUTHOR]

Rupelramphastoides knopfi, a new genus and species of the Pici (barbets, woodpeckers, and allies), is described from Frauenweiler, a Lower Oligocene (30-34 mya) fossil site in Germany. The disarticulated skeleton of the new species constitutes the first associated remains of a fossil member of the Pici and is the smallest known species and earliest substantial fossil record of this taxon. Despite an overall resemblance to modern Ramphastidae, R. knopfi appears to be distinguished from crown group Pici by several plesiomorphic characteristics. It is classified "family incertae sedis," pending discovery of additional, better-preserved specimens. The fossil record and geographic occurrence of the basal lineages within the crown group are in concordance with an Old World origin of the Pici. The reasons that led to extinction of tiny Pici in Europe remain uncertain, but food competition with passeriform birds during periods of limited food availability may have played a major role. [ABSTRACT FROM AUTHOR]

Phage-inducible chromosomal islands (PICIs) represent a novel and universal class of mobile genetic elements, which have broad impact on bacterial virulence. In spite of their relevance, how the Gram-negative PICIs hijack the phage machinery for their own specific packaging and how they block phage reproduction remains to be determined. Using genetic and structural analyses, we solve the mystery here by showing that the Gram-negative PICIs encode a protein that simultaneously performs these processes. This protein, which we have named Rpp (for redirecting phage packaging), interacts with the phage terminase small subunit, forming a heterocomplex. This complex is unable to recognize the phage DNA, blocking phage packaging, but specifically binds to the PICI genome, promoting PICI packaging. Our studies reveal the mechanism of action that allows PICI dissemination in nature, introducing a new paradigm in the understanding of the biology of pathogenicity islands and therefore of bacterial pathogen evolution. • PICI Rpp protein promotes PICI transfer while blocking phage reproduction • Rpp forms a heterocomplex with helper phage TerS • Crystal structures of Rpp alone or complexed with TerS were determined • TerS complexed with Rpp switches specificity from the phage DNA to the PICI genome Fillol-Salom et al. report that Gram-negative PICIs employ the Rpp protein to block helper phage reproduction. Rpp binds to helper phage TerS, and the Rpp-TerS heterocomplex enables PICIs to hijack the phage machinery for their own packaging. These findings reveal a mechanism used by Gram-negative PICIs to spread in nature. [ABSTRACT FROM AUTHOR]