Lupinus albus plants acquire mercury tolerance when inoculated with an Hg-resistant Bradyrhizobium strain.

One strain of Bradyrhizobium canariense (L-7AH) was selected for its metal-resistance and ability to nodulate white lupin (Lupinus albus L.) plants, from a collection of rhizobial strains previously created from soils of the Almadén mining district (Spain) with varying levels of Hg contamination. Plants were inoculated with either strain L-7AH (Hg-tolerant) or L-3 (Hg-sensitive, used as control), and watered with nutrient solutions supplemented with various concentrations (0-200 μM) of HgCl2 in a growth chamber.

Definition of a novel symbiovar (sv. retamae) within Bradyrhizobium retamae sp. nov., nodulating Retama sphaerocarpa and Retama monosperma.

In this paper we analyze through a polyphasic approach several Bradyrhizobium strains isolated in Spain and Morocco from root nodules of Retama sphaerocarpa and Retama monosperma. All the strains have identical 16S rRNA genes and their closest relative species is Bradyrhizobium lablabi CCBAU 23086(T), with 99.41% identity with respect to the strain Ro19(T).

Differential effectiveness of novel and old legume-rhizobia mutualisms: implications for invasion by exotic legumes.

The degree of specialization in the legume-rhizobium mutualism and the variation in the response to different potential symbionts are crucial factors for understanding the process of invasion by exotic legumes and the consequences for the native resident plants and bacteria. The enhanced novel mutualism hypothesis predicts that exotic invasive legumes would take advantage of native rhizobia present in the invaded soils. However, recent studies have shown that exotic legumes might become invasive by using exotic introduced microsymbionts, and that they could be a source of exotic bacteria for native legumes.

Mercury-resistant rhizobial bacteria isolated from nodules of leguminous plants growing in high Hg-contaminated soils.

A survey of symbiotic bacteria from legumes grown in high mercury-contaminated soils (Almadén, Spain) was performed to produce a collection of rhizobia which could be well adapted to the environmental conditions of this region and be used for restoration practices. Nineteen Hg-tolerant rhizobia were isolated from nodules of 11 legume species (of the genera Medicago, Trifolium, Vicia, Lupinus, Phaseolus, and Retama) and characterized. Based on their growth on Hg-supplemented media, the isolates were classified into three susceptibility groups.

Characterization of rhizobia from legumes of agronomic interest grown in semi-arid areas of Central Spain relates genetic differences to soil properties.

A study of symbiotic bacteria from traditional agricultural legumes from Central Spain was performed to create a collection of rhizobia from soils differing in physicochemical, analytical and/or agroecological properties which could be well-adapted to the environmental conditions of this region, and be used for sustainable agricultural practices. Thirty-six isolates were obtained from root-nodules of fifteen legume species (including Cicer arietinum, Lathyrus sativus, Lens culinaris, Lupinus spp., Medicago sativa, Phaseolus vulgaris, Pisum sativum, and Vicia spp.

Stress tolerance, genetic analysis and symbiotic properties of root-nodulating bacteria isolated from Mediterranean leguminous shrubs in Central Spain.

Nine root-nodulating bacterial isolates were obtained from the leguminous shrubs Spartium junceum, Adenocarpus hispanicus, Cytisus purgans, Cytisus laburnuum, Retama sphaerocarpa and Colutea arborescens in areas of Central Spain. A poliphasic approach analyzing phenotypic, symbiotic and genetic properties was used to study their diversity and characterize them in relation to Mediterranean conditions. Stress tolerance assays revealed marked variations in salinity, extreme pH and cadmium tolerance compared with reference strains, with the majority showing salinity, alkalinity and Cd tolerance and three of them growing at acid pH.

Molecular characterization and evaluation of mycorrhizal capacity of Suillus isolates from central Spain for the selection of fungal inoculants.

Suillus fungal specimens of pine forests from a Mediterranean area of central Spain (Madrid region) were studied based on molecular and physiological analysis of sporocarps to obtain fungal native inocula to produce mycorrhizal Pinus halepensis Miller in nursery. Variation within the internal transcribed spacer (ITS) region of the ribosomal RNA genes of Suillus was examined by restriction fragment length polymorphism (RFLP) and direct sequencing of polymerase chain reaction products. Ribosomal DNA (rDNA) spacers were amplified from pure cultures obtained from fruit bodies of a range of Suillus species: Suillus bellinii (Inzenga) Watling, Suillus bovinus (Pers.

Colonisation of Pinus halepensis roots by Pseudomonas fluorescens and interaction with the ectomycorrhizal fungus Suillus granulatus.

Colonisation of Pinus halepensis roots by GFP-tagged Pseudomonas fluorescens Aur6 was monitored by epifluorescence microscopy and dilution plating. Aur6-GFP was able to colonise and proliferate on P. halepensis roots.

Differential interactions within the Caenorhabditis elegans-Pseudomonas aeruginosa pathogenesis model.

A pathogenesis model based on the interaction between Caenorhabditis elegans and bacterial opportunistic pathogens has recently been developed. In the case of Pseudomonas aeruginosa, the model is based on three different modes of nematode killing (fast killing, slow killing and lethal paralysis) by virulent bacteria that has been incubated in different nutrient media. Using parametric statistics and Probit analysis, we test the reliability of the three different killing systems with respect to bacterial virulence.

Isolation, characterization, and antifungal susceptibility of melanin-deficient mutants of Scedosporium prolificans.

Scedosporium prolificans mutants lacking the ability to synthesize melanin were selected after ultraviolet light (UV) irradiation. UV exposure of S. prolificans conidia resulted in a high frequency of melanin-deficient (mel-) mutants.

Fitness of in vitro selected Pseudomonas aeruginosa nalB and nfxB multidrug resistant mutants.

Overproduction of multidrug resistance (MDR) efflux pumps is involved in the resistance to a wide range of compounds in bacteria. These determinants extrude antibiotics, but also bacterial metabolites like quorum-sensing signals. Non-regulated extrusion of bacterial metabolites might produce a metabolic burden, so that MDR-overproducing mutants could have a reduced fitness when compared with their parental strains.