Lichen-associated bacteria antagonistic to phytopathogens and their potentialto accumulate polyhydroxyalkanoates

Abstract: Bacteria are known to produce polyhydroxyalkanoates (PHA) as a storage substance,which has properties similar to those of petroleum-derived Polypropylene. Therefore, it isimportant to find PHA producing bacteria, which cope with industrial demands. Amongterrestrial ecosystems, the highly active lichen-associated bacterial communities are expected tobe a bio-resource for PHA-producers. Bacteria associated with the lichens Peltigera canina,Lobaria pulmonata, L. immixta, L. virens and Pseudocyphellaria aurata, collected from differentEuropean countries, were isolated and tested for their ability to antagonize the phytopathogenicfungi Rhizoctonia solani and Verticillium dahliae. Antagonists were subsequently screened ontheir ability to produce PHAs by applying a multiphasic approach. In a first step, a cultivationindependent method was developed to determine the occurrence of gene phaC within themicrobial community of different lichens. Using cultivation-dependent techniques, bacterialisolates from different lichens were tested on PHA accumulation in vitro employing a plate assay.In addition, the presence of the PHA synthase gene phaC was determined using PCR analysis.This study indicates that the thalli space of lichens contains a remarkable and very interestingpopulation of PHA-producing bacteria, and more studies should be conducted to understandmuch better the interaction and function of these bacteria in lichens as well as their potential forbiocontrol strategies. In conclusion, lichen habitats are an excellent source for PHA-accumulatingbacteria.