Photoautotrophic symbiont and geography are major factors affecting highly structured and diverse bacterial communities in the lichen microbiome. Public

Brendan P. Hodkinson, Neil R. Gottel, Christopher W. Schadt and François Lutzoni 2012 January 02 Environ Microbiol. 2012 Jan;14(1):147-61. doi: 10.1111/j.1462-2920.2011.02560.x. Epub 2011 Sep 12.
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Although common knowledge dictates that the lichen thallus is formed solely by a fungus (mycobiont) that develops a symbiotic relationship with an alga and/or cyanobacterium (photobiont), the non-photoautotrophic bacteria found in lichen microbiomes are increasingly regarded as integral components of lichen thalli. For this study, comparative analyses were conducted on lichen-associated bacterial communities to test for effects of photobiont-types (i.e. green algal vs. cyanobacterial), mycobiont-types and large-scale spatial distances (from tropical to arctic latitudes). Amplicons of the 16S (SSU) rRNA gene were examined using both Sanger sequencing of cloned fragments and barcoded pyrosequencing. Rhizobiales is typically the most abundant and taxonomically diverse order in lichen microbiomes; however, overall bacterial diversity in lichens is shown to be much higher than previously reported. Members of Acidobacteriaceae, Acetobacteraceae, Brucellaceae and sequence group LAR1 are the most commonly found groups across the phylogenetically and geographically broad array of lichens examined here. Major bacterial community trends are significantly correlated with differences in large-scale geography, photobiont-type and mycobiont-type. The lichen as a microcosm represents a structured, unique microbial habitat with greater ecological complexity and bacterial diversity than previously appreciated and can serve as a model system for studying larger ecological and evolutionary principles.


Figure 1. Non-metric multidimensional scaling plots produced from OTU-based Bray-Curtis dissimilarities. The first plot (A) shows results obtained from clone library data of 16S sequences from the order Rhizobiales, while the second plot (B) was produced from 454 barcoded 16S amplicon data representing approximately half the number of samples but ∼100 times as many sequences from a much wider range of bacterial diversity. Continuous lines act as visual aids to delimit communities associated with the two major photobiont-types, whereas dashed lines delimit communities associated with chlorolichens from northern versus southern sites.

Figure 3. Relative abundances of bacterial taxa recovered from each lichen sample analysed with 454 sequencing. Taxa included are the classes with > 0.1% of 16S sequences in the full 454 data set, orders with > 0.5% of sequences, and ‘families’ with > 1% of sequences; at each rank, all sequences that did not fit into one of these categories were classified as ‘other’. Photobiont is indicated by the bar across the top of the figure (light green = green algae; dark blue = Cyanobacteria), while the site is indicated with symbols immediately below the bar (• = Eagle Summit, AK; + = Nome, AK; x = Highlands, NC, and * = Cerro de la Muerte, CR). Mycobionts are indicated by name along the base of the figure.


Hodkinson, B. P., Gottel, N. R., Schadt, C. W. and Lutzoni, F. (2012), Photoautotrophic symbiont and geography are major factors affecting highly structured and diverse bacterial communities in the lichen microbiome. Environmental Microbiology, 14: 147–161. doi: 10.1111/j.1462-2920.2011.02560.x

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