dependence of the cyanobacterium prochlorococcus on hydrogen peroxide scavenging microbes for growth at the oceans surface依赖的藻青菌原经济增长对过氧化氢清除微生物球藻在海洋的表面.pdfVIP

Dependence of the Cyanobacterium Prochlorococcus on Hydrogen Peroxide Scavenging Microbes for Growth at the Ocean’s Surface 1 2 1 3 1 J. Jeffrey Morris , Zackary I. Johnson , Martin J. Szul , Martin Keller , Erik R. Zinser * 1 Department of Microbiology, University of Tennessee, Knoxville, Tennessee, United States of America, 2 Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, North Carolina, United States of America, 3 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America Abstract The phytoplankton community in the oligotrophic open ocean is numerically dominated by the cyanobacterium Prochlorococcus, accounting for approximately half of all photosynthesis. In the illuminated euphotic zone where Prochlorococcus grows, reactive oxygen species are continuously generated via photochemical reactions with dissolved organic matter. However, Prochlorococcus genomes lack catalase and additional protective mechanisms common in other aerobes, and this genus is highly susceptible to oxidative damage from hydrogen peroxide (HOOH). In this study we showed that the extant microbial community plays a vital, previously unrecognized role in cross-protecting Prochlorococcus from oxidative damage in the surface mixed layer of the oligotrophic ocean. Microbes are the primary HOOH sink in marine systems, and in the absence of the microbial community, surface waters in the Atlantic and Pacific Ocean accumulated HOOH to concentrations that were lethal for Prochlorococcus cultures. In laboratory experiments with the marine heterotroph Alteromonas sp., serving as a