Nitrogen fixing bacteria in Tuber magnatum ascocarps.

Tuber magnatum, an ascomycetous fungus and obligate ectomycorrhizal symbiont, fonns hypogeous fruit bodies, commonIy called ltalian white truffles. Although there have been several advances in truffle biology, many aspects remain unclear and the factors which may control the T. magnatum life cycle, such . as spore germination, mycorrhiza and fruit body formation, are still unknown. It has been demonstrated that certain bacteria influence the sporocarp formation, in this study we analyzed the potential activity of nitrogen fixing bacteria in T. magnatum ascocarps. These bacteria could play an important role in the ascoma formtion supplying the nitrogen required during the ascoma development in the soil. In this study we perfonned a combined molecular and biochemical approach to determine whether the Tuber-associated bacteria posses the nitrogen fixation genes and wheter these genes are expressed. To verify the prseence of the nitrogenase aperon universal primers for the conserved domains of nifH genes were applied for a nested PCR on the total DNA extracted from ascocarps at different degree of maturation and the nitrogen-fixation activity has been evaluated in the same samples by the ARA test under axenic condition. The results obtained in this study presented the first time evidence of nitrogen-fixation activity in truffles and offered the first sequence for the nifH gene described in Tuber-associated bacteria.