title: Nutrient scavenging activity and antagonistic factors of non-photobiont lichen-associated bacteria: a review.
abstract: Lichens are defined as the specific symbiotic structure comprising a fungus and a green alga and/or cyanobacterium. Up until recently, non-photobiont endothallic bacteria, while known to be present in large numbers, have generally been dismissed as functionally irrelevant cohabitants of the lichen thallus, or even environmental contaminants. Recent analyses of lichen metagenomes and innovative co-culture experiments have uncovered a functionally complex community that appears to contribute to a healthy lichen thallus in several ways. Lichen-associated bacteriomes are typically dominated by several lineages of Proteobacteria, some of which may be specific for lichen species. Recent work has implicated members of these lineages in several important ecophysiological roles. These include nutrient scavenging, including mobilization of iron and phosphate, nitrogen fixation, cellulase, xylanase and amylase activities, and oxidation of recalcitrant compounds, e.g. aromatics and aliphatics. Production of volatile organic compounds, conferring antibacterial and antifungal activity, has also been demonstrated for several lichen-associated isolates. In the present paper we review the nature of non-phototrophic endolichenic bacteria associated with lichens, and give insight into the current state of knowledge on their importance the lichen symbiotic association.
authors.affiliation: Department of Natural Resource Sciences, University of Akureyri, Borgir vid Nordurslod, 600, Akureyri, Iceland. mas@unak.is.|Faculty of Life and Environmental Sciences, University of Iceland, 101, Reykjavík, Iceland. mas@unak.is.
authors.forename: M Auður
authors.initials: MA
authors.lastname: Sigurbjörnsdóttir
authors.affiliation: Faculty of Life and Environmental Sciences, University of Iceland, 101, Reykjavík, Iceland.|Biomedical Center, University of Iceland, Vatnsmýrarvegur 16, 101, Reykjavík, Iceland.
authors.forename: Ólafur S
authors.initials: ÓS
authors.lastname: Andrésson
authors.affiliation: Department of Natural Resource Sciences, University of Akureyri, Borgir vid Nordurslod, 600, Akureyri, Iceland.|Biomedical Center, University of Iceland, Vatnsmýrarvegur 16, 101, Reykjavík, Iceland.
authors.forename: Oddur
authors.initials: O
authors.lastname: Vilhelmsson
mesh_terms: D000890:Anti-Infective Agents / Q000378:metabolism; D054884:Host-Pathogen Interactions; D008011:Lichens / Q000382:microbiology*; D054892:Metagenome; D009586:Nitrogen Fixation; D020560:Proteobacteria / Q000502:physiology*; D013559:Symbiosis; D055549:Volatile Organic Compounds / Q000378:metabolism
chemical_list: D000890:Anti-Infective Agents; D055549:Volatile Organic Compounds
keywords: Bacteria; Endothallic; Lichen; Microbiome; Symbiosis