Bacteria associated with truffle‐fruiting bodies contribute to truffle aroma

Abstract

SummaryTruffles, symbiotic fungi renown for the captivating aroma of their fruiting bodies, are colonized by a complex bacterial community of unknown function. We characterized the bacterial community of the white truffle Tuber borchii and tested the involvement of its microbiome in the production of sulphur-containing volatiles. We found that sulphur-containing volatiles such as thiophene derivatives, characteristic of T. borchii fruiting bodies, resulted from the biotransformation of non-volatile precursor(s) into volatile compounds by bacteria. The bacterial community of T. borchii was dominated by α-and β-Proteobacteria. Interestingly, all bacteria phyla/classes tested in this study were able to produce thiophene volatiles from T. borchii fruiting body extract, irrespective of their isolation source (truffle or other sources). This indicates that the ability to produce thiophene volatiles might be widespread among bacteria and possibly linked to primary metabolism. Treatment of fruiting bodies with antibacterial agents fully suppressed the production of thiophene volatiles while fungicides had no inhibitory effect. This suggests that during the sexual stage of truffles, thiophene volatiles are exclusively synthesized by bacteria and not by the truffle. At this stage, the origin of thiophenes precursor in T. borchii remains elusive and the involvement of yeasts or other bacteria cannot be excluded.

The Role of the Microbiome of Truffles in Aroma Formation: a Meta-Analysis Approach

“…To date, microbes and microbial communities have been characterized in truffles with culture-dependent and -independent techniques in Ͼ15 papers (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(17)(18)(19)(20)(21). Various life cycle stages of four commercially relevant Tuber species have been investigated: the white truffles T. magnatum and T. borchii and the black species T. melanosporum and T. aestivum.…”

“…1) (4,5,(12)(13)(14)19). Similarities among fruiting bodies of the three truffle species investigated to date include a dominance of Alphaproteobacteria and a relative paucity of Firmicutes and Actinobacteria.…”

“…This might be due to modifications in physicochemical parameters, such as temperature and CO 2 level (23). For example, Splivallo et al (14) observed the appearance of colonies belonging to Firmicutes and Actinobacteria, while the abundance of members of Alphaproteobacteria and Betaproteobacteria decreased in fruiting bodies of T. borchii after 6 days of postharvest storage at room temperature (14).…”

“…Their fruiting bodies are appreciated for their distinctive aroma, which is partially derived from microbes (6,14,16). The aim of this minireview is to synthesize the current knowledge on the composition of the microbial community of truffles and discuss their potential role in truffle aroma formation, specifically focusing on volatiles that are responsible for human-perceived truffle aroma (defined as odorants).…”

“…Recent high-throughput molecular techniques have revolutionized the field of microbial ecology by unraveling an enormous microbial diversity in numerous organisms and highlighting the deep impact of microbiomes of their host physiology and behavior (1,2). Truffle fungi are no exception, since they are colonized by a complex microbial community made up of bacteria, yeasts, guest filamentous fungi, and viruses (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14).…”