Defining traits of low-light adapted Prochlorococcus inhabiting surface waters of the Equatorial Pacific Ocean
- 1Massachusetts Institute of Technology
Abstract
A diverse array of photosynthetic phytoplankton drives primary production in equatorial surface waters. Among these, the cyanobacterium Prochlorococcus is an important contributor to net primary production in these typically iron-limited, high-nutrient and low-chlorophyll (HNLC) regions. Here, we explore the diversity of these organisms, in part, through targeted enrichment of Prochlorococcus cells using field-based high-speed cell sorting techniques. We demonstrate that the genomes of Prochlorococcus belonging to the low-light adapted LLI clade, and isolated from the surface of the Equatorial Pacific Ocean, are depleted in functions related to the assimilation of urea, nitrite, and amino acids. These are the first examples of LLI Prochlorococcus that have lost the ability to use nitrite, a trait considered to be a core feature of this clade. All new equatorial cultures of LLI Prochlorococcus appear to use a distinct isoform of protoporphyrinogen IX oxidase (HemG), for the biosynthesis of a chlorophyll precursor, that does not require the use of iron-containing heme. In contrast, the heme-dependent HemJ isoform is typically used by Prochlorococcus found outside equatorial HNLC waters. Together, these findings suggest that low-light adapted Prochlorococcus in the equatorial ocean possess accessory gene content that reflects adaptation to the generally iron-limited but nitrogen-replete conditions of surface waters.
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BibTeX
@misc{berube2026defining,
title = {{Defining traits of low-light adapted Prochlorococcus inhabiting surface waters of the Equatorial Pacific Ocean}},
author = {P. M. Berube and T. LeMaster and K. R. Cain and Y. Raut and Z. Bartolek and S. Graff van Creveld and L. Arsenieff and K. Kunde and S. Sulcius and A. Coe and N. L. Fisher and S. Blaskowski and A. E. Jones-Kellett and D. Lindell and R. M. Bundy and V. Armbrust and S. W. Chisholm},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.23.753768},
url = {https://www.biorxiv.org/content/10.64898/2026.09.23.753768v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Defining traits of low-light adapted Prochlorococcus inhabiting surface waters of the Equatorial Pacific Ocean
AU - P. M. Berube
AU - T. LeMaster
AU - K. R. Cain
AU - Y. Raut
AU - Z. Bartolek
AU - S. Graff van Creveld
AU - L. Arsenieff
AU - K. Kunde
AU - S. Sulcius
AU - A. Coe
AU - N. L. Fisher
AU - S. Blaskowski
AU - A. E. Jones-Kellett
AU - D. Lindell
AU - R. M. Bundy
AU - V. Armbrust
AU - S. W. Chisholm
PY - 2026
DA - 2026/09/23
PB - bioRxiv
DO - 10.64898/2026.09.23.753768
UR - https://www.biorxiv.org/content/10.64898/2026.09.23.753768v1
AB - A diverse array of photosynthetic phytoplankton drives primary production in equatorial surface waters. Among these, the cyanobacterium Prochlorococcus is an important contributor to net primary production in these typically iron-limited, high-nutrient and low-chlorophyll (HNLC) regions. Here, we explore the diversity of these organisms, in part, through targeted enrichment of Prochlorococcus cells using field-based high-speed cell sorting techniques. We demonstrate that the genomes of Prochlorococcus belonging to the low-light adapted LLI clade, and isolated from the surface of the Equatorial Pacific Ocean, are depleted in functions related to the assimilation of urea, nitrite, and amino acids. These are the first examples of LLI Prochlorococcus that have lost the ability to use nitrite, a trait considered to be a core feature of this clade. All new equatorial cultures of LLI Prochlorococcus appear to use a distinct isoform of protoporphyrinogen IX oxidase (HemG), for the biosynthesis of a chlorophyll precursor, that does not require the use of iron-containing heme. In contrast, the heme-dependent HemJ isoform is typically used by Prochlorococcus found outside equatorial HNLC waters. Together, these findings suggest that low-light adapted Prochlorococcus in the equatorial ocean possess accessory gene content that reflects adaptation to the generally iron-limited but nitrogen-replete conditions of surface waters.
ER -