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1.  Exploring the plant-associated bacterial communities in Medicago sativa L 
BMC Microbiology  2012;12:78.
Background
Plant-associated bacterial communities caught the attention of several investigators which study the relationships between plants and soil and the potential application of selected bacterial species in crop improvement and protection. Medicago sativa L. is a legume crop of high economic importance as forage in temperate areas and one of the most popular model plants for investigations on the symbiosis with nitrogen fixing rhizobia (mainly belonging to the alphaproteobacterial species Sinorhizobium meliloti). However, despite its importance, no studies have been carried out looking at the total bacterial community associated with the plant. In this work we explored for the first time the total bacterial community associated with M. sativa plants grown in mesocosms conditions, looking at a wide taxonomic spectrum, from the class to the single species (S. meliloti) level.
Results
Results, obtained by using Terminal-Restriction Fragment Length Polymorphism (T-RFLP) analysis, quantitative PCR and sequencing of 16 S rRNA gene libraries, showed a high taxonomic diversity as well as a dominance by members of the class Alphaproteobacteria in plant tissues. Within Alphaproteobacteria the families Sphingomonadaceae and Methylobacteriaceae were abundant inside plant tissues, while soil Alphaproteobacteria were represented by the families of Hyphomicrobiaceae, Methylocystaceae, Bradyirhizobiaceae and Caulobacteraceae. At the single species level, we were able to detect the presence of S. meliloti populations in aerial tissues, nodules and soil. An analysis of population diversity on nodules and soil showed a relatively low sharing of haplotypes (30-40%) between the two environments and between replicate mesocosms, suggesting drift as main force shaping S. meliloti population at least in this system.
Conclusions
In this work we shed some light on the bacterial communities associated with M. sativa plants, showing that Alphaproteobacteria may constitute an important part of biodiversity in this system, which includes also the well known symbiont S. meliloti. Interestingly, this last species was also found in plant aerial part, by applying cultivation-independent protocols, and a genetic diversity analysis suggested that population structure could be strongly influenced by random drift.
doi:10.1186/1471-2180-12-78
PMCID: PMC3412730  PMID: 22607312
2.  An Italian functional genomic resource for Medicago truncatula 
BMC Research Notes  2008;1:129.
Background
Medicago truncatula is a model species for legumes. Its functional genomics have been considerably boosted in recent years due to initiatives based both in Europe and US. Collections of mutants are becoming increasingly available and this will help unravel the genetic control of important traits for many species of legumes.
Findings
Our report is on the production of three complementary mutant collections of the model species Medicago truncatula produced in Italy in the frame of a national genomic initiative. Well established strategies were used: Tnt1 mutagenesis, TILLING and activation tagging. Both forward and reverse genetics screenings proved the efficiency of the mutagenesis approaches adopted, enabling the isolation of interesting mutants which are in course of characterization. We anticipate that the reported collections will be complementary to the recently established functional genomics tools developed for Medicago truncatula both in Europe and in the United States.
doi:10.1186/1756-0500-1-129
PMCID: PMC2633015  PMID: 19077311
3.  Genetic Diversity and Dynamics of Sinorhizobium meliloti Populations Nodulating Different Alfalfa Cultivars in Italian Soils 
Applied and Environmental Microbiology  2000;66(11):4785-4789.
We analyzed the genetic diversity of 531 Sinorhizobium meliloti strains isolated from nodules of Medicago sativa cultivars in two different Italian soils during 4 years of plant growth. The isolates were analyzed for DNA polymorphism with the random amplified polymorphic DNA method. The populations showed a high level of genetic polymorphism distributed throughout all the isolates, with 440 different haplotypes. Analysis of molecular variance allowed us to relate the genetic structure of the symbiotic population to various factors, including soil type, alfalfa cultivar, individual plants within a cultivar, and time. Some of these factors significantly affected the genetic structure of the population, and their relative influence changed with time. At the beginning of the experiment, the soil of origin and, even more, the cultivar significantly influenced the distribution of genetic variability of S. meliloti. After 3 years, the rhizobium population was altered; it showed a genetic structure based mainly on differences among plants, while the effects of soil and cultivar were not significant.
PMCID: PMC92380  PMID: 11055924

Results 1-3 (3)