AUTHOR=Zhang Yanying , Yang Qingsong , Ling Juan , Van Nostrand Joy D. , Shi Zhou , Zhou Jizhong , Dong Junde 

TITLE=The Shifts of Diazotrophic Communities in Spring and Summer Associated with Coral Galaxea astreata, Pavona decussata, and Porites lutea

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01870

DOI=10.3389/fmicb.2016.01870

ISSN=1664-302X

ABSTRACT=<p>The coral holobiont often resides in oligotrophic waters; both coral cells and their symbiotic dinoflagellates possess ammonium assimilation enzymes and potentially benefit from the nitrogen fixation of coral-associated diazotrophs. However, the seasonal dynamics of coral-associated diazotrophs are not well characterized. Here, the seasonal variations of diazotrophic communities associated with three corals, <italic>Galaxea astreata, Pavona decussata</italic>, and <italic>Porites lutea</italic>, were studied using <italic>nifH</italic> gene amplicon pyrosequencing techniques. Our results revealed a great diversity of coral-associated diazotrophs. <italic>nifH</italic> sequences related to <italic>Alphaproteobacteria, Deltaproteobacteria</italic>, and <italic>Gammaproteobacteria</italic> were ubiquitous and dominant in all corals in two seasons. In contrast with the coral <italic>P. decussata</italic>, both <italic>G. astreata</italic> and <italic>P. lutea</italic> showed significant seasonal changes in the diazotrophic communities and <italic>nifH</italic> gene abundance. Variable diazotroph groups accounted for a range from 11 to 49% within individual coral samples. Most of the variable diazotrophic groups from <italic>P. decussata</italic> were species-specific, however, the majority of overlapping variable groups in <italic>G. astreata</italic> and <italic>P. lutea</italic> showed the same seasonal variation characteristics. <italic>Rhodopseudomonas palustris</italic>- and <italic>Gluconacetobacter diazotrophicus</italic>-affiliated sequences were relatively abundant in the summer, whereas a <italic>nifH</italic> sequence related to <italic>Halorhodospira halophila</italic> was relatively abundant in spring <italic>G. astreata</italic> and <italic>P. lutea</italic>. The seasonal variations of all diazotrophic communities were significantly correlated with the seasonal shifts of ammonium and nitrate, suggesting that diazotrophs play an important role in the nitrogen cycle of the coral holobiont.</p>