Peroxisome Proliferation in Foraminifera Inhabiting the Chemocline: An Adaptation to Reactive Oxygen Species Exposure?



    1. Geology and Geophysics Department, MS 52, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, and
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    1. Wadsworth Center, New York State Department of Health, P. O. Box 509, Albany, New York 12201-0509, and Department of Biomedical Sciences, The University at Albany, Albany, New York 12222
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  • 1Invited presentation delivered during the joint annual meeting of the Phycological Society of America and the International Society of Protistologists, Providence, Rhode Island, August 5–9, 2007.

Corresponding Author: J. M. Bernhard, Geology and Geophysics Department, MS 52, Woods Hole Oceanographic Institution, Woods Hole, MA 02543—Telephone number: 508 289 3480; FAX number: 508 457 2076; e-mail:


ABSTRACT. Certain foraminiferal species are abundant within the chemocline of marine sediments. Ultrastructurally, most of these species possess numerous peroxisomes complexed with the endoplasmic reticulum (ER); mitochondria are often interspersed among these complexes. In the Santa Barbara Basin, pore-water bathing Foraminifera and co-occurring sulfur-oxidizing microbial mats had micromolar levels of hydrogen peroxide (H2O2), a reactive oxygen species that can be detrimental to biological membranes. Experimental results indicate that adenosine triphosphate concentrations are significantly higher in Foraminifera incubated in 16 μM H2O2 than in specimens incubated in the absence of H2O2. New ultrastructural and experimental observations, together with published results, lead us to propose that foraminiferans can utilize oxygen derived from the breakdown of environmentally and metabolically produced H2O2. Such a capability could explain foraminiferal adaptation to certain chemically inhospitable environments; it would also force us to reassess the role of protists in biogeochemistry, especially with respect to hydrogen and iron. The ecology of these protists also appears to be tightly linked to the sulfur cycle. Finally, given that some Foraminifera bearing peroxisome–ER complexes belong to evolutionarily basal groups, an early acquisition of the capability to use environmental H2O2 could have facilitated diversification of foraminiferans during the Neoproterozoic.