PCR primers based on different portions of insertion elements can assist phylogeny studies, strain fingerprinting and species identification in rhizobia.

Using the sequence of an insertion element originally found in Rhizobium sullae, the nitrogen-fixing bacterial symbiont of the legume Hedysarum coronarium, we devised three primer pairs (inbound, outbound and internal primers) for the following applications: (a) tracing genetic relatedness within rhizobia using a method independent of ribosomal inheritance, based on the presence and conservation of IS elements; (b) achieve sensitive and reproducible bacterial fingerprinting; (c) enable a fast and unambiguous detection of rhizobia at the species level. In terms of taxonomy, while in line with part of the 16S rRNA gene- and glutamine synthetase I-based clustering, the tools appeared nonetheless more coherent with the actual geographical ranges of origin of rhizobial species, strengthening the European-Mediterranean connections and discerning them from the asian and american taxa. The fingerprinting performance of the outward-pointing primers, designed upon the inverted repeats, was shown to be at least as sensitive as BOX PCR, and to be functional on a universal basis with all 13 bacterial species tested. The primers designed on the internal part of the transposase gene instead proved highly species-specific for R. sullae, enabling selective distinction from its most related species, and testing positive on every R. sullae strain examined, fulfilling the need of PCR-mediated species identification. A general use of other IS elements for a combined approach to rhizobial taxonomy and ecology is proposed

Characterization of endophytic and symbiotic bacteria within plants of the endemic association Centaureetum horridae Mol.

We investigated the internal association of bacteria with Astragalus terraccianoi and Centaurea horrida, two endemic plants of the Mediterranean islands, forming the phytosociological association Centaureetum horridae, typical of windswept cliffs on the rocky shores of Asinara (Sardinia, Italy) and other limited locations. Sampling occurred in the protected natural park of the Asinara island. Roots and stems of the two plants and the root nodules of A. terraccianoi were surface sterilized in order to remove external and rhizospheric microbiota and to subsequently isolate the culturable bacterial communities. Plate counts revealed densities of endophytes between 3.7 7 102 and 2.8 7 104 colony forming units per gram of fresh weight. 16S rDNA sequencing revealed the occurrence of bacteria displaying high similarity with Actinobacterium sp., Paenibacillus sp., Rhizobium sp., Methylobacterium sp., Pedobacter panaciterrae, Aerococcus viridans, Stenotrophomonas rhizophila, Bacillus sporothermodurans, Bacillus pumilus, Bacillus simplex, Bacillus flexus, Streptomyces ciscaucasicus and Dyella sp. The putative nitrogen-fixing rhizobium symbiont of A. terraccianoi was identified for the first time. It turned out to belong to the slow-growing Bradyrhizobium genus and to share a 97% similarity with Bradyrhizobium canariense. It was found to be nonculturable and to coexist in nodules with a number of different endophytes

Concurrent mapping of an adenovirus 5/SV40 integration site and the U1 snRNA cluster (RNU1) within 400 kb of the chromosome region 1p36.1.

Previous reports from our group suggested the preferential integration of the viral construct Ad5/SV40 at the short arm subtelomeric region of human chromosome 1. The present study narrows the region of viral integration to site 1p36.1 in a close cytogenetic overlap with the U1 snRNA gene cluster (RNU1) within a distance necessarily smaller than 400 kb as suggested by the size of the YAC in which the two markers were found to coexist. This finding supports the hypothesis that the chromosomal site in question may have a constitutional propensity to genetic recombination

Wild legume root nodules as a potential reservoir for human pathogenic bacteria.

A previous finding by our group (Benhizia et al., 2004) shows that root nodules from wild legumes, besides their natural rhizobium symbionts, can host and multiply bacteria belonging to species pathogenic to humans. These include Enterobacter cloacae, Enterobacter kobei, Escherichia vulneris, Leclercia adecarboxylata, Pantoea agglomerans. As these taxa were repeatedly found in nodules from three plant species, differing by habitat ecophysiology, and harvested in independent natural sites which are spaced apart up to 150 Km from each other, we believe that the phenomenon can be a general feature and have potentially significant impacts for the epidemiology of bacteria of clinical interest. In the sole Italian territory nearly four hundred species of wild leguminous plants are known, whose microbiological interactions are largely unknown. These plants can nevertheless develop abundant root nodules, which are optimal sites for bacterial multiplication. Wild legume distribution can span over a series of habitats, ranging from urban-synanthropic, to agricultural, and to the majority of natural habitats. In light of the above findings, yielding five Enterobacterial taxa of potential danger to humans from the analysis of only three species of wild plants, one could envisage the biomass of wild legumes as possible strategic niche for the survival and active multiplication of clinical pathogens in hosts alternative to mammals