Cryptic bacterial pathogens of diatoms peak during senescence of a winter diatom bloom

Branscombe, L, Harrison, EL, Choong, ZYD, Swink, C, Keys, M, Widdicombe, CE, Wilson, WH, Cunliffe, M and Helliwell, KE 2023 Cryptic bacterial pathogens of diatoms peak during senescence of a winter diatom bloom. New Phytologist, 241 (3). 1292-1307. https://doi.org/10.1111/nph.19441

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Abstract/Summary

Diatoms are globally abundant microalgae that form extensive blooms in aquatic ecosystems. Certain bacteria behave antagonistically towards diatoms, killing or inhibiting their growth. Despite their crucial implications to diatom blooms and population health, knowledge of diatom antagonists in the environment is fundamentally lacking. We report systematic characterisation of the diversity and seasonal dynamics of bacterial antagonists of diatoms via plaque assay sampling in the Western English Channel (WEC), where diatoms frequently bloom. Unexpectedly, peaks in detection did not occur during char�acteristic spring diatom blooms, but coincided with a winter bloom of Coscinodiscus, suggesting that these bacteria likely influence distinct diatom host populations. We isolated multiple bacterial antagonists, spanning 4 classes and 10 bacterial orders. Notably, a diatom attaching Roseobacter Ponticoccus alexandrii was isolated multiple times, indi�cative of a persistent environmental presence. Moreover, many isolates had no prior reports of antagonistic activity towards diatoms. We verified diatom growth inhibitory effects of eight isolates. In all cases tested, these effects were activated by pre-exposure to diatom organic matter. Discovery of widespread ‘cryptic’ antagonistic activity indicates that bacterial pathogenicity towards diatoms is more prevalent than previously recognised. Finally, examination of the global biogeography of WEC antagonists revealed co-occurrence patterns with diatom host populations in marine waters globally.

Item Type:	Publication - Article
Additional Keywords:	algicidal, Coscinodiscus, diatom–bacteria interactions, diatoms, plaque assay, Ponticoccus.
Divisions:	Plymouth Marine Laboratory > National Capability categories > Single Centre NC - CLASS (expired) Plymouth Marine Laboratory > National Capability categories > Western Channel Observatory Plymouth Marine Laboratory > Science Areas > Marine Ecology and Biodiversity
Depositing User:	S Hawkins
Date made live:	29 Feb 2024 10:57
Last Modified:	29 Feb 2024 10:57
URI:	https://plymsea.ac.uk/id/eprint/10131

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