Phototroph-heterotroph interactions during growth and long-term starvation across Prochlorococcus and Alteromonas diversity

Osnat Weissberg, Dikla Aharonovich, Daniel Sher

Research output: Contribution to journalArticlepeer-review


Due to their potential impact on ecosystems and biogeochemistry, microbial interactions, such as those between phytoplankton and bacteria, have been studied intensively using specific model organisms. Yet, to what extent interactions differ between closely related organisms, or how these interactions change over time, or culture conditions, remains unclear. Here, we characterize the interactions between five strains each of two globally abundant marine microorganisms, Prochlorococcus (phototroph) and Alteromonas (heterotroph), from the first encounter between individual strains and over more than a year of repeated cycles of exponential growth and long-term nitrogen starvation. Prochlorococcus-Alteromonas interactions had little effect on traditional growth parameters such as Prochlorococcus growth rate, maximal fluorescence, or lag phase, affecting primarily the dynamics of culture decline, which we interpret as representing cell mortality and lysis. The shape of the Prochlorococcus decline curve and the carrying capacity of the co-cultures were determined by the phototroph and not the heterotroph strains involved. Comparing various mathematical models of culture mortality suggests that Prochlorococcus death rate increases over time in mono-cultures but decreases in co-cultures, with cells potentially becoming more resistant to stress. Our results demonstrate intra-species differences in ecologically relevant co-culture outcomes. These include the recycling efficiency of N and whether the interactions are mutually synergistic or competitive. They also highlight the information-rich growth and death curves as a useful readout of the interaction phenotype.

Original languageEnglish
Number of pages11
JournalISME Journal
Issue number2
StatePublished - Feb 2023

Bibliographical note

Funding Information:
We thank Sher lab members and especially Natalie Andrawes for help in fluorescence measurements and Daniel Segrè, Hans-Peter Grossart, Zhen Wu and Tal Luzzatto Knaan for critical reading of the manuscript. This work was supported by the Human Frontiers Science Program (grant RGP0020/2016, to DS), the Israel Science Foundation (grant 1786/20 to DS), and the U.S.-Israel Binational Science Foundation (BSF) - U.S. National Science Foundation (NSF) program in Oceanography (grant 1635070/2016532, to DS). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Publisher Copyright:
© 2022, The Author(s).

ASJC Scopus subject areas

  • Microbiology
  • Ecology, Evolution, Behavior and Systematics


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