AUTHOR=Mancuso Francesco P. , D'Hondt Sofie , Willems Anne , Airoldi Laura , De Clerck Olivier 

TITLE=Diversity and Temporal Dynamics of the Epiphytic Bacterial Communities Associated with the Canopy-Forming Seaweed Cystoseira compressa (Esper) Gerloff and Nizamuddin

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00476

DOI=10.3389/fmicb.2016.00476

ISSN=1664-302X

ABSTRACT=<p>Canopy-forming seaweed species of the genus <italic>Cystoseira</italic> form diverse and productive habitats along temperate rocky coasts of the Mediterranean Sea. Despite numerous studies on the rich macrofauna and flora associated with <italic>Cystoseira</italic> spp., there is little knowledge about the epiphytic bacteria. We analyzed bacterial populations associated with canopies of <italic>Cystoseira compressa</italic>, over an annual vegetative cycle (May-October), and their relationships with the bacterial populations in the surrounding seawater, at intertidal rocky shores in Vasto (Chieti—Italy). The bacterial diversity was assessed using Illumina Miseq sequences of V1-V3 hypervariable regions of 16S rRNA gene. <italic>C. compressa</italic> bacterial community was dominated by sequences of <italic>Proteobacteria</italic> and <italic>Bacteroidetes, Verrucomicrobia, Actinobacteria</italic>, and <italic>Cyanobacteria</italic> especially of the <italic>Rhodobacteriaceae, Flavobacteriaceae, Sapropiraceae, Verrucomicrobiaceae</italic>, and <italic>Phyllobacteriaceae</italic> families. Seawater libraries were also dominated by <italic>Proteobacteria</italic> and <italic>Bacteroidetes</italic> sequences, especially of the <italic>Candidatus Pelagibacter</italic> (SAR11) and <italic>Rhodobacteriaceae</italic> families, but were shown to be clearly distinct from <italic>C. compressa</italic> libraries with only few species in common between the two habitats. We observed a clear successional pattern in the epiphytic bacteria of <italic>C. compressa</italic> over time. These variations were characterized by gradual addition of OTUs (<italic>Verrucomicrobia, Actinobacteria</italic> and SR1) to the community over a growing season, indicative of a temporal gradient, rather than a radical reorganization of the bacterial community. Moreover, we also found an increase in abundance over time of <italic>Rhodobacteraceae</italic>, comprising six potential pathogenic genera, <italic>Ruegeria, Nautella, Aquimarina, Loktanella, Saprospira</italic>, and <italic>Phaeobacter</italic> which seemed to be associated to aged thalli of <italic>C. compressa</italic>. These bacteria could have the potential to affect the health and ecology of the algae, suggesting the hypothesis of a possible, but still unexplored, role of the microbial communities in contributing to the extensive ongoing declines of populations of <italic>Cystoseira</italic> spp. in the Mediterranean Sea.</p>