Anoxygenic phototrophic Chlorobi use broad metabolic and resource acquisition strategies to support stable near-clonal blooms
- 1Florida Atlantic University
Abstract
Anoxygenic phototrophic green sulfur bacteria (GSB; Chlorobiia) are important primary producers in anoxic and sulfidic environments, whose significance in aquatic ecosystems will expand with coastal deoxygenation. Here, we employed a uniquely comprehensive analytical approach to investigate the formation, maintenance, and collapse of a GSB bloom. We combined multi-omics -- V4V5 and synthetic long read 16S rRNA amplicon sequencing, metagenomics, and metaproteomics -- with total and GSB-specific cell counts, biogeochemical measurements, and isotopic analysis. The GSB bloom exceeded 109 cells ml-1, among the highest environmental cell densities reported to date, with up to 96 % of the bloom consisting of a single strain-level Prosthecochloris lineage (GSB-TRL01). Extreme sulfide concentrations (> 17 mM) coincided with peaking cell density and a shift in isotopic composition. Bloom persistence is supported by tightly coupled sulfur cycling, high rates of nitrogen fixation, mechanisms to tolerate oxidative stress and maintain redox balance, and nutrient acquisition through outer membrane transport systems. A shift in sulfur oxidizing enzymes towards enzymes with higher sulfide affinity proceeded bloom demise. Prosthecochloris GSB-TRL01 differs from closely related lineages in several outer membrane transport systems, including porins to transport phosphate and tonB-dependent transporters. Collectively, these findings identify physiological and metabolic strategies that may enable near-clonal Prosthecochloris populations to attain extraordinary biomass while coupling the sulfur, carbon, and nitrogen cycles in coastal euxinic environments.
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BibTeX
@misc{moynihan2026anoxygenic,
title = {{Anoxygenic phototrophic Chlorobi use broad metabolic and resource acquisition strategies to support stable near-clonal blooms}},
author = {M. A. Moynihan and O. L. Mathieson and C. A. Crowley and E. Greene and H. Vanderscheuren and D. Dumit and R. Weed and K. Koop-Jakobsen and M. Kleiner and S. E. Ruff},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.24.754110},
url = {https://www.biorxiv.org/content/10.64898/2026.09.24.754110v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Anoxygenic phototrophic Chlorobi use broad metabolic and resource acquisition strategies to support stable near-clonal blooms
AU - M. A. Moynihan
AU - O. L. Mathieson
AU - C. A. Crowley
AU - E. Greene
AU - H. Vanderscheuren
AU - D. Dumit
AU - R. Weed
AU - K. Koop-Jakobsen
AU - M. Kleiner
AU - S. E. Ruff
PY - 2026
DA - 2026/09/24
PB - bioRxiv
DO - 10.64898/2026.09.24.754110
UR - https://www.biorxiv.org/content/10.64898/2026.09.24.754110v1
AB - Anoxygenic phototrophic green sulfur bacteria (GSB; Chlorobiia) are important primary producers in anoxic and sulfidic environments, whose significance in aquatic ecosystems will expand with coastal deoxygenation. Here, we employed a uniquely comprehensive analytical approach to investigate the formation, maintenance, and collapse of a GSB bloom. We combined multi-omics -- V4V5 and synthetic long read 16S rRNA amplicon sequencing, metagenomics, and metaproteomics -- with total and GSB-specific cell counts, biogeochemical measurements, and isotopic analysis. The GSB bloom exceeded 109 cells ml-1, among the highest environmental cell densities reported to date, with up to 96 % of the bloom consisting of a single strain-level Prosthecochloris lineage (GSB-TRL01). Extreme sulfide concentrations (> 17 mM) coincided with peaking cell density and a shift in isotopic composition. Bloom persistence is supported by tightly coupled sulfur cycling, high rates of nitrogen fixation, mechanisms to tolerate oxidative stress and maintain redox balance, and nutrient acquisition through outer membrane transport systems. A shift in sulfur oxidizing enzymes towards enzymes with higher sulfide affinity proceeded bloom demise. Prosthecochloris GSB-TRL01 differs from closely related lineages in several outer membrane transport systems, including porins to transport phosphate and tonB-dependent transporters. Collectively, these findings identify physiological and metabolic strategies that may enable near-clonal Prosthecochloris populations to attain extraordinary biomass while coupling the sulfur, carbon, and nitrogen cycles in coastal euxinic environments.
ER -