Articles | Volume 14, issue 2
Research article
23 Jan 2017
Research article |  | 23 Jan 2017

Diversity and mineral substrate preference in endolithic microbial communities from marine intertidal outcrops (Isla de Mona, Puerto Rico)

Estelle Couradeau, Daniel Roush, Brandon Scott Guida, and Ferran Garcia-Pichel

Abstract. Endolithic microbial communities are prominent features of intertidal marine habitats, where they colonize a variety of substrates, contributing to their erosion. Almost 2 centuries worth of naturalistic studies focused on a few true-boring (euendolithic) phototrophs, but substrate preference has received little attention. The Isla de Mona (Puerto Rico) intertidal zone offers a unique setting to investigate substrate specificity of endolithic communities since various phosphate rock, limestone and dolostone outcrops occur there. High-throughput 16S rDNA genetic sampling, enhanced by targeted cultivation, revealed that, while euendolithic cyanobacteria were dominant operational taxonomic units (OTUs), the communities were invariably of high diversity, well beyond that reported in traditional studies and implying an unexpected metabolic complexity potentially contributed by secondary colonizers. While the overall community composition did not show differences traceable to the nature of the mineral substrate, we detected specialization among particular euendolithic cyanobacterial clades towards the type of substrate they excavate but only at the OTU phylogenetic level, implying that close relatives have specialized recurrently into particular substrates. The cationic mineral component was determinant in this preference, suggesting the existence in nature of alternatives to the boring mechanism described in culture that is based exclusively on transcellular calcium transport.

Short summary
Endoliths are a prominent bioerosive component of intertidal marine habitats, traditionally thought to be formed by a few cyanobacteria, algae and fungi. Using molecular techniques, however, we found that endoliths from Mona Island, Puerto Rico, were of high diversity, well beyond that reported in traditional studies. We also found evidence for substrate specialization, in that closely related cyanobacteria seem to have diversified to specialize recurrently to excavate various mineral substrates
Final-revised paper