17 Bacteria and the Lichen Symbiosis

Lichens are more complex symbioses than previously thought. Lichen symbioses include, beside other fungi, significant amounts of bacterial associates. Work in the recent past revealed the diversity of lichen-associated bacterial communities and confirmed their host-specific nature. New knowledge exists about the parameters that contribute to variations in the composition of bacterial communities within and among thalli of the same lichenized fungal species. The biological roles of bacteria in lichens are not clearly validated at present, but first evidence from culture-dependent and culture-independent approaches suggest the contribution of bacteria to several possible functions in the lichen symbiosis. Lichens are also a rich source of new bacterial lineages as well as novel and useful bacterial compounds. Finally we point on the biotechnological potential of lichen-associated bacteria.