Direct detection and isolation of plasmid-bearing virulent serotypes of Yersinia enterocolitica from various foods.

A procedure was developed for direct detection, isolation, and maintenance of plasmid-bearing virulent serotypes of Yersinia enterocolitica from different food sources. Plasmid-bearing virulent strains of Y. enterocolitica representing five serotypes were simultaneously detected and isolated from enriched swab samples of artificially contaminated pork chops, ground pork, cheese, and zucchini, using Congo red binding and low-calcium-response tests. The method was also effective in isolating plasmid-bearing virulent strains of Y. enterocolitica from naturally contaminated porcine tongues. Virulence of the strains isolated from these foods was confirmed by PCR, the expression of plasmid-associated phenotypes, and mouse pathogenicity.     

Use of a single procedure for selective enrichment, isolation, and identification of plasmid-bearing virulent Yersinia enterocolitica of various serotypes from pork samples.

Many selective enrichment methods for the isolation of Yersinia enterocolitica from foods have been described. However, no single isolation procedure has been described for the recovery and identification of various plasmid-bearing serotypes. A single improved procedure for selective enrichment, isolation, identification, and maintenance of plasmid-bearing virulent serotypes of Y. enterocolitica from pork samples was developed. Enrichment at 12 degrees C in Trypticase soy broth containing yeast extract, bile salts, and Irgasan was found to be an efficient medium for the recovery of plasmid-bearing virulent strains of Y. enterocolitica representing O:3; O:8; O:TACOMA; O:5, O:27; and O:13 serotypes. MacConkey agar proved to be a reliable medium for the isolation of presumptive colonies, which were subsequently confirmed as plasmid-bearing virulent strains by Congo red binding and low calcium response. Further confirmation by multiplex PCR employed primers directed at the chromosomal ail and plasmid-borne virF genes, which are present only in pathogenic strains. The method was applied to pig slaughterhouse samples and was effective in isolating plasmid-bearing virulent strains of Y. enterocolitica from naturally contaminated porcine tongues. Strains isolated from ground pork and tongue expressed plasmid-associated phenotypes and mouse pathogenicity.     

Flux Analysis of Glucose Metabolism in Rhizopus oryzae for the Purpose of Increasing Lactate Yields

A flux analysis of glucose metabolism in the filamentous fungus Rhizopus oryzae was achieved using a specific radioactivity curve-matching program, TFLUX. Glycolytic and tricarboxylic acid cycle intermediates labeled through the addition of extracellular [U-14C]glucose were isolated and purified for specific radioactivity determinations. This information, together with pool sizes and the rates of glucose utilization and end product production, provided input for flux maps of the metabolic network under two different experimental conditions. Based upon the flux analysis of this system, a mutant of R. oryzae with higher lactate and lower ethanol yields than the parent was sought for and found.     

The Effect of Coumarin on Growth, Production of Dry Matter, Protein and Nucleic Acids in Roots of Maize and Wheat and the Interaction of Coumarin with Metabolic Inhibitors

Effects of coumarin on fresh weight, dry matter, protein and nucleic acid content per cell in attached roots of maize and wheat and in whole excised elongation zones of maize were determined. The inhibition in cell length exerted by coumarin did not correspond to an inhibition of the net synthetic capacity. Coumarin treatment increased the cell surface, the production of dry matter and the protein content per cell. The dry matter and the protein content per unit surface was slightly increased or unaffected. The effect of coumann on cell shape seemed to be independent of that on dry matter production and net protein synthesis. The same was found in excised elongation zones. —The net DNA-synthesis per cell was slightly increased in attached roots by coumann treatment, but this effect was probably not correlated with the morphogenetic changes. Inhibition of DNA-synthesis with hydroxyurea did not alter the coumarin induced changes in cell shape. —The net RNA-synthesis per cell was slightly decreased after coumarin treatment, but the net RNA-synthesis per cell and the morphogenetic effects exerted by coumarin were not related with each other. Inhibition of m-RNA-synthesis with actinomycin D did not prevent the effects of coumarin on cell division, cell expansion, dry matter production and net protein synthesis. The same was true for inhibitors of protein synthesis, puromycin and p-fluorophenyl-alanine. The findings are in support of the view that coumarin affects already existing structures or enzymes. —Comparisons between coumarin and the uncouplers, DNP and dicoumarol, showed that the effects of coumarin were not, solely, due to uncoupling. SH-protecting agents, BAL, DTE and glutathione, did, with few exceptions, not reduce the morphogenetic effects of coumarin.     

High Abundances of Aerobic Anoxygenic Photosynthetic Bacteria in the South Pacific Ocean

Little is known about the abundance, distribution, and ecology of aerobic anoxygenic phototrophic (AAP) bacteria, particularly in oligotrophic environments, which represent 60% of the ocean. We investigated the abundance of AAP bacteria across the South Pacific Ocean, including the center of the gyre, the most oligotrophic water body of the world ocean. AAP bacteria, Prochlorococcus, and total prokaryotic abundances, as well as bacteriochlorophyll a (BChl a) and divinyl-chlorophyll a concentrations, were measured at several depths in the photic zone along a gradient of oligotrophic conditions. The abundances of AAP bacteria and Prochlorococcus were high, together accounting for up to 58% of the total prokaryotic community. The abundance of AAP bacteria alone was up to 1.94 × 10⁵ cells ml⁻¹ and as high as 24% of the overall community. These measurements were consistent with the high BChl a concentrations (up to 3.32 × 10⁻³ μg liter⁻¹) found at all stations. However, the BChl a content per AAP bacterial cell was low, suggesting that AAP bacteria are mostly heterotrophic organisms. Interestingly, the biovolume and therefore biomass of AAP bacteria was on average twofold higher than that of other prokaryotic cells. This study demonstrates that AAP bacteria can be abundant in various oligotrophic conditions, including the most oligotrophic regime of the world ocean, and can account for a large part of the bacterioplanktonic carbon stock.     

Adaptive Introgression Facilitates Adaptation to High Latitudes in European Aspen (Populus tremula L.)

Understanding local adaptation has become a key research area given the ongoing climate challenge and the concomitant requirement to conserve genetic resources. Perennial plants, such as forest trees, are good models to study local adaptation given their wide geographic distribution, largely outcrossing mating systems, and demographic histories. We evaluated signatures of local adaptation in European aspen (Populus tremula) across Europe by means of whole-genome resequencing of a collection of 411 individual trees. We dissected admixture patterns between aspen lineages and observed a strong genomic mosaicism in Scandinavian trees, evidencing different colonization trajectories into the peninsula from Russia, Central and Western Europe. As a consequence of the secondary contacts between populations after the last glacial maximum, we detected an adaptive introgression event in a genome region of ∼500 kb in chromosome 10, harboring a large-effect locus that has previously been shown to contribute to adaptation to the short growing seasons characteristic of Northern Scandinavia. Demographic simulations and ancestry inference suggest an Eastern origin—probably Russian—of the adaptive Nordic allele which nowadays is present in a homozygous state at the north of Scandinavia. The strength of introgression and positive selection signatures in this region is a unique feature in the genome. Furthermore, we detected signals of balancing selection, shared across regional populations, that highlight the importance of standing variation as a primary source of alleles that facilitate local adaptation. Our results, therefore, emphasize the importance of migration–selection balance underlying the genetic architecture of key adaptive quantitative traits.     

Phylogenomic species delimitation and host‐symbiont coevolution in the fungus‐farming ant genus Sericomyrmex Mayr (Hymenoptera: Formicidae): ultraconserved elements (UCEs) resolve a recent radiation

Ants in the Neotropical genus Sericomyrmex Mayr cultivate fungi for food. Both ants and fungi are obligate, coevolved symbionts. The taxonomy of Sericomyrmex is problematic because the morphology of the worker caste is generally homogeneous across all of the species within the genus, species limits are vague, and the relationships between them are unknown. We used ultraconserved elements (UCEs) as genome‐scale markers to reconstruct evolutionary history and to infer species boundaries in Sericomyrmex. We recovered an average of ～990 UCE loci for 88 Sericomyrmex samples from across the geographical range of the genus as well as for five outgroup taxa. Using maximum likelihood and species‐tree approaches, we recovered nearly identical topologies across datasets with 50–95% matrix completeness. We identify nine species‐level lineages in Sericomyrmex, including two new species. This is less than the previously described 19 species, even accounting for two species for which we had no UCE samples, which brings the total number of Sericomyrmex species to 11. Divergence‐dating analyses recovered 4.3 Ma as the crown‐group age estimates for Sericomyrmex, indicating a recent, rapid radiation. We also sequenced mitochondrial cytochrome oxidase subunit I (COI) for 125 specimens. Resolution and support for clades in our COI phylogeny are weak, indicating that COI is not an appropriate species‐delimitation tool. However, taxa within species consistently cluster together, suggesting that COI is useful as a species identification (‘DNA barcoding’) tool. We also sequenced internal transcribed spacer (ITS) and large subunit (LSU) for 32 Sericomyrmex fungal cultivars. The fungal phylogeny confirms that Sericomyrmex fungi are generalized higher‐attine cultivars, interspersed with Trachymyrmex‐associated fungal species, indicating cultivar sharing and horizontal transfer between these two genera. Our results indicate that UCEs offer immense potential for delimiting and resolving relationships of problematic, recently diverged species.     

Functional consequences of heterogeneous gap junction channel formation and its influence in health and disease

The capacity of multiple connexins to hetero-oligomerize into functional heterogeneous gap junction channels has been demonstrated in vivo¹, in vitro², and in nonmammalian expression systems. These heterogeneous channels display gating activity, channel conductances, selectivity and regulatory behaviors that are sometimes not predicted by the behaviors of the corresponding homogeneous channels. Such observations suggest that heteromerization of gap junction proteins offers an efficient cellular strategy for finely regulating cell-to-cell communication. The available evidence strongly indicates that heterogeneous gap junction assembly is important to normal growth and differentiation, and may influence the appearance of several disease states. Definitive evidence that heterogeneous gap junction channels differentially regulate electrical conduction in excitable cells is absent. This review examines the prevalence, regulation, and implications of gap junction channel hetero-oligomerization.