ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Aquatic Microbiology
This article is part of the Research TopicProtistan Phagotrophy and the Far-reaching ImplicationsView all 4 articles
Using Acidic Vesicle Tracer to Identify Potential Bacterivores in Coastal Waters of the Subtropical Western Pacific Ocean
Provisionally accepted
- 1National Taiwan Ocean University, Keelung, Taiwan
- 2General Education Center, National Taiwan Ocean University, Keelung, Taiwan
- 3Institute of Marine Environment and Ecology, College of Ocean Science and Resource, National Taiwan Ocean University, Keelung, Taiwan
- 4Fisheries Research Institute, Council of Agriculture, keelung, Keelung County, Taiwan
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Bacterivores play a key role in transferring energy through microbial food webs and are broadly classified as heterotrophic or mixotrophic based on the presence of inherent chloroplasts. Mixotrophs, especially in low-latitude regions, have recently gained attention due to their dual roles as primary producers and bacterial grazers, which enable them to thrive in nutrient-poor, stratified waters where traditional autotrophs or heterotrophs may be less competitive. This study investigated the composition of bacterivores in the coastal waters of northeastern Taiwan during the warm season (July and August 2022). A combination of LysoTracker staining, flow cytometry sorting, and 18S rRNA gene amplicon sequencing was used to rapidly identify heterotrophic and mixotrophic nanoflagellates (HNFs and MNFs, respectively) based on chloroplast autofluorescence. The dominant eukaryotic lineages included Alveolata, Stramenopiles, Opisthokonta, Chlorophyta, and Rhizaria. HNFs were primarily composed of MAST clades, choanoflagellates (Opisthokonta), Telonemia, and Radiolaria, while MNFs included cryptophytes, haptophytes, and chlorophytes such as Mamiella and Mantoniella, as well as stramenopiles like Dictyochophyceae and Chrysophyceae. Notably, several non-motile chlorophytes, including Chloropicon and members of Pycnococcaceae, were identified as potential bacterivores based on Lysotracker signals; however, their phagotrophic capability requires further confirmation in future studies. Despite the limitations of LysoTracker-based methods, this study reveals previously overlooked mixotrophic diversity and highlights the need for further validation. These findings advance our understanding of carbon flow and microbial dynamics in subtropical marine ecosystems under changing environmental conditions.
Keywords: 18S rRNA gene amplicon, Flow cytometric cell sorting, heterotrophy LysoTracker, mixotrophy, bacterivores
Received: 29 Mar 2025; Accepted: 05 Nov 2025.
Copyright: © 2025 Lin, Lin, Chiang, Chin and Chou. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Yun-Chi Lin, d96310001@gmail.com
Kuoping Chiang, kpchiang@mail.ntou.edu.tw
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