Hodkinson, Brendan P. , Lutzoni, Francois .
Do lichens harbor their own 'rhizobia'? A large-scale phylogenetic survey of lichen-associated bacteria from the order Rhizobiales.
Although common knowledge dictates that the lichen thallus is formed solely by a fungus that develops a symbiotic relationship with an alga and/or cyanobacterium, lichen-associated non-photobiont bacteria are increasingly regarded as significant players in the ecology and physiology of the lichen microbiome. Since many lichens are able to grow on extremely nutrient-poor substrates, it has been suggested that these bacteria may provide some lichen thalli with a substantial source of fixed nitrogen and other crucial nutrients. For this study, community-wide comparative analyses were conducted on lichen-associated bacteria from the order Rhizobiales. Clone libraries of the 16S (SSU) rRNA gene were constructed from nearly 400 lichen samples (collected in Alaska, North Carolina, and Costa Rica) that are diverse in terms of chemistry, photobiont type, mycobiont, and growth form. Comparative analyses of sequence libraries indicate that major bacterial community differences are correlated most strongly with photobiont type. A large component of this trend is likely due to differing nitrogen requirements in cyanobacterial vs. green-algal lichens. Phylogenetic data also support the notion that different types of lichen thalli may act as specialized niches for specific undescribed lineages of bacteria from the Rhizobiales, suggesting the possibility of co-evolution between certain lichens and their proteobacterial associates.
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1 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 552A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 4:45 PM