Document Type
Article
Department/Program
Virginia Institute of Marine Science
Publication Date
2015
Journal
Proceedings Of The National Academy Of Sciences Of The United States Of America
Volume
112
Issue
32
First Page
9938
Last Page
9943
Abstract
Southern Ocean primary productivity plays a key role in global ocean biogeochemistry and climate. At the Southern Ocean sea ice edge in coastal McMurdo Sound, we observed simultaneous cobalamin and iron limitation of surface water phytoplankton communities in late Austral summer. Cobalamin is produced only by bacteria and archaea, suggesting phytoplankton-bacterial interactions must play a role in this limitation. To characterize these interactions and investigate the molecular basis of multiple nutrient limitation, we examined transitions in global gene expression over short time scales, induced by shifts in micronutrient availability. Diatoms, the dominant primary producers, exhibited transcriptional patterns indicative of co-occurring iron and cobalamin deprivation. The major contributor to cobalamin biosynthesis gene expression was a gammaproteobacterial population, Oceanospirillaceae ASP10-02a. This group also contributed significantly to metagenomic cobalamin biosynthesis gene abundance throughout Southern Ocean surface waters. Oceanospirillaceae ASP10-02a displayed elevated expression of organic matter acquisition and cell surface attachment-related genes, consistent with a mutualistic relationship in which they are dependent on phytoplankton growth to fuel cobalamin production. Separate bacterial groups, including Methylophaga, appeared to rely on phytoplankton for carbon and energy sources, but displayed gene expression patterns consistent with iron and cobalamin deprivation. This suggests they also compete with phytoplankton and are important cobalamin consumers. Expression patterns of siderophore-related genes offer evidence for bacterial influences on iron availability as well. The nature and degree of this episodic colimitation appear to be mediated by a series of phytoplankton-bacterial interactions in both positive and negative feedback loops.
DOI
10.1073/pnas.1501615112
Keywords
Ross Sea; Summer Bacterioplankton; Community Structure; Iron Limitation; Surface Waters; Vitamin-B-12; Identification; Dimethylsulfide; Metabolism; Flavodoxin
Recommended Citation
Bertrand, EM; McCrow, JP; Moustafa, A; Zheng, H; McQuaid, JB; Post, AF; Sipler, Rachel E.; Spackeen, JL; Xu, K; Bronk, DA; Hutchins, DA; and Allen, AE, Phytoplankton-bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge (2015). Proceedings Of The National Academy Of Sciences Of The United States Of America, 112(32), 9938-9943.
10.1073/pnas.1501615112
