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. 2025 Nov:149:102956.
doi: 10.1016/j.hal.2025.102956. Epub 2025 Aug 19.

First report of nodularin production by Nostochopsis sp. in a temperate eutrophic lake

Abby M Webster  1 , Zac Triumph  2 , Bofan Wei  2 , Robbie M Martin  3 , Laura E Smith  3 , Steven W Wilhelm  3 , Lisa B Cleckner  4 , N Roxanna Razavi  5 , Gregory L Boyer  2
Affiliations

First report of nodularin production by Nostochopsis sp. in a temperate eutrophic lake

Abby M Webster et al. Harmful Algae. 2025 Nov.

Abstract

Benthic cyanobacteria are understudied in comparison to their planktonic counterparts. Consequently, our understanding of cyanotoxin production in benthic mats remains limited. We detected nodularin-R (NOD-R) in a population of Nostochopsis from Honeoye Lake (New York, United States). Identification as Nostochopsis was supported by morphological (see section 3.1 for a detailed description) and metagenomic analyses. The first metagenome assembled genome of Nostochopsis was drafted and estimated at 99.28 % complete. Cyanotoxin testing of Nostochopsis biomass showed production of NOD-R but not microcystins, anatoxins, or cylindrospermopsins. The complete nodularin synthetase cluster was confirmed in the Nostochopsis genome. To our knowledge, this is the first report of nodularin production, or any cyanotoxin production, by the benthic cyanobacteria Nostochopsis. This is the fourth genus of cyanobacteria reported to produce nodularins.

Keywords: Benthic cyanobacteria; Cyanotoxin; Freshwater; Hepatotoxin.

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Conflict of interest statement

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1.
Fig. 1.
(A) Macroscopic photo of Nostochopsis colonies collected from Honeoye Lake in 2023. Colonies varied in shape and size and were mucilaginous to touch. A zebra mussel (~ 2 cm) on the right edge of rock shows scale of colony sizes. (B and C) Microscopic images of Nostochopsis taken at 400x magnification. (D) A third microscopic image taken at 400x and zoomed in for visual purposes. True branching of filaments is visible with heterocytes positioned at the ends of short lateral branches.
Fig. 2.
Fig. 2.
Offset chromatograms of m/z 825.4 (NOD-R) channel from analysis of samples 22–464 (rt = 10.27 min), 23–1105 (rt = 10.25 min), 23–1106 (rt = 10.28 min), and 24–1968 (rt = 10.24 min) alongside a 0.5 ppm NOD-R standard (rt = 10.24 min) and a blank using Single Quad method outline in Section 2.3. The beginning of each sample number (i.e., “22″ “23″ and “24”) refer to the year the sample was collected and extracted.
Fig. 3.
Fig. 3.
A Maximum Likelihood tree of 16S rDNA sequences of Nostochopsis sp. strain Haneayah (in red) and closely related taxa. Bootstrap values as a percentage of replicate trees supporting the node are reported.
Fig. 4.
Fig. 4.
Nodularin biosynthetic gene cluster from Nostochopsis sp. Haneayah drafted genome compared to the original description of the gene cassette from N. spumigena NSOR10 (Moffitt and Neilan, 2004). Darker shading between genes of each sequence represents more similar identity (%). The specific identity comparisons (%) are available in Table S4.
See this image and copyright information in PMC

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