Native Plasmid-Encoded Mercury Resistance Genes Are Functional and Demonstrate Natural Transformation in Environmental Bacterial Isolates.

Plasmid-mediated horizontal gene transfer (HGT) is a major driver of genetic diversity in bacteria. We experimentally validated the function of a putative mercury resistance operon present on an abundant 8-kbp native plasmid found in groundwater samples without detectable levels of mercury. Phylogenetic analyses of the plasmid-encoded mercury reductases from the studied groundwater site show them to be distinct from those reported in proximal metal-contaminated sites. We synthesized the entire native plasmid and demonstrated that the plasmid was sufficient to confer functional mercury resistance in Escherichia coli Given the possibility that natural transformation is a prevalent HGT mechanism in the low-cell-density environments of groundwaters, we also assayed bacterial strains from this environment for competence. We used the native plasmid-encoded metal resistance to design a screen and identified 17 strains positive for natural transformation. We selected 2 of the positive strains along with a model bacterium to fully confirm HGT via natural transformation. From an ecological perspective, the role of the native plasmid population in providing advantageous traits combined with the microbiome's capacity to take up environmental DNA enables rapid adaptation to environmental stresses.IMPORTANCE Horizontal transfer of mobile genetic elements via natural transformation has been poorly understood in environmental microbes. Here, we confirm the functionality of a native plasmid-encoded mercury resistance operon in a model microbe and then query for the dissemination of this resistance trait via natural transformation into environmental bacterial isolates. We identified 17 strains including Gram-positive and Gram-negative bacteria to be naturally competent. These strains were able to successfully take up the plasmid DNA and obtain a clear growth advantage in the presence of mercury. Our study provides important insights into gene dissemination via natural transformation enabling rapid adaptation to dynamic stresses in groundwater environments

Winterhardiness, Forage Production, and Persistence of Introduced and Native Grasses and Legumes in Southcentral Alaska

This study consisted of four separate field experiments, each of six years duration, conducted at the University of Alaska’s Matanuska Research Farm (61.6oN) near Palmer in southcentral Alaska. Objectives were to compare winterhardiness, forage productivity, and general persistence of introduced grass and legume species, strains, and cultivars from various world sources with Alaska-developed cultivars and native Alaskan species. Twenty-one species of grasses compared (Tables 1 through 4) included eight native to Alaska, four Alaska cultivars, and numerous introduced cultivars and regional strains (one to seven per species) from North America and northern Europe. Legumes included two species of biennial sweetclover and nine species of perennials, six introduced and three native. Each experiment was harvested once near the end of the seeding year and twice annually for five years thereafter

Draft Genome Sequences of Four Saccharibacter sp. Strains Isolated from Native Bees.

The genus Saccharibacter is currently understudied, with only one described species, Saccharibacter floricola, isolated from a flower. In an effort to better understand the microbes that come in contact with native bee pollinators, we isolated and sequenced four additional strains of Saccharibacter from native bees in the genera Melissodes and Anthophora These genomes range in size from 2,104,494 to 2,316,791 bp (mean, 2,246,664 bp) and contain between 1,860 and 2,167 (mean, 2,060) protein-coding genes

Bromegrass in Alaska. I.Winter Survival and Forage Productivity of Bromus Species, Types, and Cultivars as Related to Latitudinal Adaptation

This report summarizes seven separate field experiments, conducted over more than two decades at the University of Alaska’s Matanuska Research Farm, that compared strains within three bromegrass (Bromus) species for winter hardiness and forage production. Species were (a) smooth bromegrass (B. inermis Leyss.), (b) native Alaskan pumpelly bromegrass (B. pumpellianus Scribn.), and (c) meadow bromegrass (B. biebersteinii Roem. and Schult.), a species native to southwestern Asia

Symbiotic and phylogenetic diversity of rhizobia associated with native and introduced Acacias in Algeria

In the arid zones were crop production is reduced due to drought combined to low soil fertility, the use of symbiotic native legume trees adapted to such harsh conditions could enhance the productivity of agroforestry systems. In North Africa, Acacia species are good candidates for this purpose since they can grow on N-deficient soils and improve their N balnce due to their symbiotic association with rhizobia, nitrogen-fixing soil bacteria. In order to identify and select. Efficient acacia-rhizobia symbiotic associations, soil samples and root nodules from seven Acacia species, five native (A ehrenbergiana, A laeta, A. niIotica, A. seyal, A. tortimis) and two introduced (A. karroo, A. saligna). were collected in arid and semi-arid regions of Algeria from Oran to Tamanrasset. A collection of 22 bacteria1 strains was obtained after trapping on Acacia seedlings inoculated with soil samples originating from nine geographic sites. 16S rDNA sequencing revealed that the new strains represented different species in Sinorhizobium and Rhizobium. This genetic diversity was confirmed by phenotypic characterisation through biochemical assays and host spectrum. Some strains were particularly tolerant to low pH and high NaCl concentrations. temperature and osmotic stress in vitro conditions. In a next step, selection of efficient rthizobia displaying a high nitrogen-fixing potential under stress conditions will be carried out in controlled conditions before testing them in field conditions. (Texte intégral

Bromegrass in Alaska. IV. Effects of Various Schedules and Frequencies of Harvest on Forage Yields and Quality and on Subsequent Winter Survival of Several Strains

Effects of different annual harvest schedules and frequencies on several cultivars and strains of bromegrass (Bromus species) were measured in five field experiments at the University of Alaska’s Matanuska Research Farm (61.6oN) near Palmer in southcentral Alaska. Most cultivars evaluated and compared were smooth bromegrass (B. inermis Leyss.). Native Alaskan pumpelly bromegrass (B. pumpellianus Scribn.) and the predominantly hybrid (B. inermis x B. pumpellianus) cultivar Polar, developed in Alaska, were included also

A Wolbachia triple-strain infection generates self-incompatibility in Aedes albopictus and transmission instability in Aedes aegypti.

BACKGROUND: Artificially-introduced transinfections of the intracellular bacterium Wolbachia pipientis have the potential to reduce the vectorial capacity of mosquito populations for viruses such as dengue and chikungunya. Aedes albopictus has two native strains of Wolbachia, but their replacement with the non-native wMel strain blocks transmission of both viruses. The pattern of cytoplasmic incompatiiblity generated by wMel with wild-types is bidirectional. Novel-plus-native-strain co-infection is predicted to lead to a more efficient population spread capacity; from a bi-directional to a uni-directional cytoplasmic incompatibility (CI) model. RESULTS: A novel-plus-native-strain triple-infection in Ae. albopictus (wAlbAwAlbBwMel) was generated. Although triple-infected females were fully reproductively viable with uninfected males, they displayed self-incompatibility. qPCR of specific strains in dissected tissues suggested that this may be due to the displacement of one of the native strains (wAlbA) from the ovaries of triple-infected females. When the triple strain infection was transferred into Aedes aegypti it displayed an unexpectedly low level of transmission fidelity of the three strains in this species. CONCLUSIONS: These results suggest that combining Wolbachia strains can lead to co-infection interactions that can affect outcomes of CI and maternal transmission

Bromegrass in Alaska. II. Autumn Food-Reserve Storage, Freeze Tolerance, and Dry-Matter Concentration in Overwintering Tissues as Related to Winter Survival of Latitudinal Ecotypes

The objective of this study was to acquire improved understanding of factors that influence winter survival of bromegrass (Bromus spp.) at northern latitudes. Four bromegrass strains of diverse latitudinal origins were used: (a) native Alaskan pumpelly bromegrass (B. pumpellianus Scribn.) adapted at 61° to 65°N, (b) the Alaska hybrid cultivar Polar (predominantly B. inermis Leyss. x B. pumpellianus) selected at 61.6°N, and two smooth bromegrass (B. inermis) cultivars, (c) Manchar selected in the U.S. Pacific Northwest (43° to 47°N), and (d) Achenbach originating from Kansas (34° to 42°N)

Genetic Basis of Tetracycline Resistance in Bifidobacterium animalis subsp lactis

All strains of Bifidobacterium animalis subsp. lactis described to date show medium level resistance to tetracycline. Screening of 26 strains from a variety of sources revealed the presence of tet(W) in all isolates. A transposase gene upstream of tet(W) was found in all strains, and both genes were cotranscribed in strain IPLAIC4. Mutants with increased tetracycline resistance as well as tetracycline-sensitive mutants of IPLAIC4 were isolated and genetically characterized. The native tet(W) gene was able to restore the resistance phenotype to a mutant with an alteration in tet(W) by functional complementation, indicating that tet(W) is necessary and sufficient for the tetracycline resistance seen in B. animalis subsp. lactis