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Front. Microbiol. | doi: 10.3389/fmicb.2019.00650

Biogeography of Cyanobacterial isiA Genes and their Link to Iron Availability in the Ocean

  • 1Center for Microbial Oceanography, University of Hawaii at Manoa, United States
  • 2Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Netherlands
  • 3Department of Ocean and Earth Science, National Oceanography Centre Southampton, Faculty of Natural and Environmental Sciences, University of Southampton, United Kingdom
  • 4State Key Laboratory of Marine Environmental Science, Xiamen University, China

The cyanobacterial iron-stress-inducible isiA gene encodes a chlorophyll-binding protein that provides flexibility in photosynthetic strategy enabling cells to acclimate to low iron availability. Here, information on the diversity and abundance of isiA genes are provided from 14 oceanic stations encompassing large natural gradients in iron availability. Synechococcus CRD1 and CRD2-like isiA genes were ubiquitously identified from tropical and subtropical waters of the Pacific, Atlantic and Indian Oceans. The relative abundance of isiA-containing Synechococcus cells ranged from under 10% of the total Synechococcus population in regions where iron is replete such as the North Atlantic subtropical gyre, to over 80% in low-iron but high-nitrate regions of the eastern equatorial Pacific. Interestingly, Synechococcus populations in regions with both low iron and low nitrate concentrations such as the subtropical gyres in the North Pacific and South Atlantic had a low relative abundance of the isiA gene. Indeed, fitting our data into a multiple regression model showed that ~80% of the variation in isiA relative abundances can be explained by nitrate and iron concentrations, whereas no other environmental variables (temperature, salinity, Chl a) had a significant effect. Hence, isiA has a predictable biogeographical distribution, consistent with the perceived biological role of IsiA as an adaptation to low-iron conditions. Understanding such photosynthetic strategies is critical to our ability to accurately estimate primary production and map nutrient limitation on global scales.

Keywords: Cyanobacteria, Synechoccocus, Iron limitation, Antenna protein, Isia, Chlorophyll

Received: 18 Jul 2018; Accepted: 14 Mar 2019.

Edited by:

George S. Bullerjahn, Bowling Green State University, United States

Reviewed by:

David J. Scanlan, University of Warwick, United Kingdom
Adam R. Rivers, Agricultural Research Service, United States Department of Agriculture, United States  

Copyright: © 2019 Li, Huisman, Bibby and Jiao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Nianzhi Jiao, State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, 361005, Fujian Province, China, jiao@xmu.edu.cn