Microenvironment and phylogenetic diversity of Prochloron inhabiting the surface of crustose didemnid ascidians. (11th August 2015)

• Record Type: Journal Article
• Authors: Nielsen, Daniel A.; Pernice, Mathieu; Schliep, Martin; Sablok, Gaurav; Jeffries, Thomas C.; Kühl, Michael; Wangpraseurt, Daniel; Ralph, Peter J.; Larkum, Anthony W. D.
• Is Part Of: Environmental microbiology. Volume 17:Number 10(2015:Oct.)
• Page Start: 4121
• Page End: 4132
• Publication Date: 2015-08-11
• Subjects: Microbial ecology -- Periodicals; Environmental Microbiology -- Periodicals; 579.17
• DOI: 10.1111/1462-2920.12983
• Languages: English
• ISSNs: 1462-2912

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>The cyanobacterium <italic>P</italic><italic>rochloron didemni</italic> is primarily found in symbiotic relationships with various marine hosts such as ascidians and sponges. <italic>P</italic><italic>rochloron</italic> remains to be successfully cultivated outside of its host, which reflects a lack of knowledge of its unique ecophysiological requirements. We investigated the microenvironment and diversity of <italic>P</italic><italic>rochloron</italic> inhabiting the upper, exposed surface of didemnid ascidians, providing the first insights into this microhabitat. The pH and O<sub>2</sub> concentration in this <italic>P</italic><italic>rochloron</italic> biofilm changes dynamically with irradiance, where photosynthetic activity measurements showed low light adaptation (E<sub>k</sub> ∼80 ± 7 μmol photons m<sup>−2</sup> s<sup>−1</sup>) but high light tolerance. Surface <italic>P</italic><italic>rochloron</italic> cells exhibited a different fine structure to <italic>P</italic><italic>rochloron</italic> cells from cloacal cavities in other ascidians, the principle difference being a central area of many vacuoles dissected by single thylakoids in the surface <italic>P</italic><italic>rochloron</italic>. Cyanobacterial 16S rDNA pyro‐sequencing of the biofilm community on four ascidians resulted in 433 operational taxonomic units (OTUs) where on average −85% (65–99%) of all sequence reads, represented by 136 OTUs, were identified as <italic>P</italic><italic>rochloron</italic> via <sc>blast</sc> search. All of the major <italic>P</italic><italic>rochloron</italic>‐OTUs clustered into independent, highly supported phylotypes separate from sequences reported for internal <italic>P</italic><italic>rochloron</italic>, suggesting a hitherto unexplored genetic variability among <italic>P</italic><italic>rochloron</italic> colonizing the outer surface of didemnids.</p> </abstract>