ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Aquatic Microbiology
This article is part of the Research TopicMicroalgae-Microbe Interactions: Advances and ApplicationsView all 5 articles
Continuous Passage of Predatory Oligoflexales Bacteria in Nannochloropsis oceanica
Provisionally accepted
- 1New Mexico State University, Department of Biology, Las Cruces, New Mexico, United States
- 2New Mexico State University Department of Civil Engineering, Las Cruces, United States
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The paucity of laboratory models comprising predatory bacteria infecting microalgae hinders our understanding of bacteria that predate or parasitize algae both in aquatic ecosystems as well as algal cultivation systems. In 2015, a novel predatory bacterium was found in open cultivation ponds of Nannochloropsis salina located in Las Cruces, New Mexico (NM). This bacterium, "FD111", caused the crash of large-scale cultures in the field and transfer of the infection source into healthy N. salina cultures in the lab killed them. However, research on this pest has been slow due to difficulties cultivating it under laboratory conditions. In 2023, we passaged multiple sources of an FD111-like pest into laboratory cultures of Nannochloropsis. Here, we report on the continuous passage of two infection sources into two cultures of Nannochloropsis oceanica, CCAP849/10 and a field-adapted culture of the same isolate, with the purpose of enriching for the pest. The pest was successfully passaged into healthy cultures ten times. Following each passage, infected cultures deteriorated and, after four days, died. Continued passaging of the infection source to healthy algal cultures was a reliable approach to maintain pest viability in the lab, although it did not help to enrich the pest concentration, likely due to the timing of each passage. Transmission electron microscopy showed that a pest similar to FD111 attached to N. oceanica cells, replicated inside the cells, and exited the cells after replication - leaving ghost cells. In this study, the FD111-like bacterium had a rod shape and single flagellum, whereas the originally described FD111 had two distinct phenotypes: a rod and hook shape. The 16S microbial community analysis indicated that the FD111-like bacterium falls within the Oligoflexales order, possibly Pseudobacteriovorax genus. This paper shows that continuous passage can be an alternative approach to isolation and cultivation of pests, and lays the groundwork for additional research and development on this and similar pests.
Keywords: crop protection, predatory bacterium, integrated pest management (IPM), infectionsource, FD111, Pseudobacteriovorax, Oligoflexus
Received: 23 Aug 2025; Accepted: 17 Nov 2025.
Copyright: © 2025 Nguyen, Abeykoon and Corcoran. 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: Thuy M. Nguyen, tmnguyen@nmsu.edu
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