Comparative diversity analyses of modern marine thrombolitic mats by barcoded pyrosequencing

This project aimed to characterize the microbial diversity within four distinct surface mat communities (black, beige, pink, and button) associated with an actively forming intertidal thrombolitic build-ups located in Highborne Cay, Bahamas. Three 16S rRNA gene amplicon 454 pyrosequenced libraries were generated for each thrombolitic mat: Bacteria (V2 region), Cyanobacteria (V4 region), Archaea (V5 region). A combined approach using an taxonomic analysis of OTUs at 97% similarity with the mothur sequence analysis package and a phylogenetic analysis with Fast UniFrac was used to examine differences in microbial diversity in the four thrombolitic mats. The bacterial libraries from the four mat types contained similar phyla, dominated by Proteobacteria and Cyanobacteria,that varied in abundance between each mat. There were prominent differences between the four communities in the cyanobacterial and archaeal libraries. The button mats contained the highest cyanobacterial diversity including an enrichment of Dichothrix spp. which has been associated with carbonate precipitation within thrombolitic mats. Archaeal diversity in all mat types was low and was dominated by Thaumarchaea and Euryarchaea. This study represents the first in-depth diversity analysis of thrombolitic mats using high-thoroughput sequencing and provides a foundation for understanding the interactions and metabolisms of these complex microbial communities.