What is it about?

Microbes support all marine food webs and store fossil fuel-derived carbon in the deep ocean, and it is thus crucial to understand how their growth and diversity will respond to climate warming. Marine microbiologists typically assess microbial functional diversity such as adaptation to temperature changes using genome sequencing methods. This study using cultures isolated from a coastal plankton community found that strains of the widespread marine cyanobacterium Synechococcus that are pre-adapted to growing at higher temperatures already exist unrecognized within a nearly genetically identical population. The existence of these cryptic thermal specialist strains may be due to reversible epigenomic changes that subtly modify their DNA and so control their thermal responses, rather than being caused by obvious genome sequence differences that can be easily detected with commonly used molecular techniques.

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Why is it important?

The existence of "hidden" thermal diversity in populations of marine microbes that is not detectable by standard community genome sequencing methods means that marine microbiologists may be underestimating the resilience of some populations of ocean microorganisms to future climate warming.


To better understand the responses of marine plankton communities to climate change, these findings highlight a need to incorporate laboratory culturing-based physiological studies along with commonly applied observational metagenomic sampling of in situ populations. On a hopeful note, these results suggest that some marine microbial groups critical to ocean biology and carbon cycling may be able to persist even in the face of severe ocean warming, using molecular mechanisms that have not been widely considered by the microbial oceanography community.

David Hutchins
University of Southern California

Read the Original

This page is a summary of: Dual thermal ecotypes coexist within a nearly genetically identical population of the unicellular marine cyanobacterium Synechococcus, Proceedings of the National Academy of Sciences, November 2023, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2315701120.
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