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. 2025 Jul 2;25(1):395.
doi: 10.1186/s12866-025-04085-2.

Effects of different doses of microcystin-LR exposure on gut development and the microbiota of Xenopus laevis tadpoles

Jinjin Li  1 , Yuanyuan Zhang  2 , Jiajia Ni  3 , Wenxuan Hou  2 , Lei Huang  4 , Hanping Pan  4 , Chenxu Wang  2 , Kaixin Wang  2 , Shaoyuan Zuo  2 , Jiahao Dong  2 , Mingyu Zhang  2
Affiliations

Effects of different doses of microcystin-LR exposure on gut development and the microbiota of Xenopus laevis tadpoles

Jinjin Li et al. BMC Microbiol. .

Abstract

Background: Although the acute toxicity of microcystin-LR has been widely confirmed, its effects on aquatic organisms at environmental concentrations have not been systematically studied. To reveal the effects of microcystin-LR on gut development and the microbiota of tadpoles, Xenopus laevis tadpoles were exposed to 0, 1, 5, 20, and 50 µg/L of microcystin-LR for 1, 7, 49, and 70 days (d) and the results were analyzed using histopathology, reverse transcription-quantitative polymerase chain reaction, and 16 S rRNA amplicon sequencing.

Results: Exposure to 5 µg/L microcystin-LR caused damage to the intestinal integrity and development of tadpoles, with the severity of damage increasing with higher concentrations. High concentrations of microcystin-LR (≥ 20 µg/L) significantly increased intestinal epithelial thickness over 49 d. Additionally, exposure to different concentrations of microcystin-LR had varying effects on the expression of TNF-α, IL-8, and TGF-β in the intestine, and microcystin-LR exposure at 50 µg/L continuously inhibited the expression of TGF-β. The relative abundances of Actinobacteria and Spirochaetes changed with sampling stages. In the samples taken at 49 d, Firmicutes and Tenericutes were significantly more abundant than in other samples, whereas Proteobacteria were significantly less abundant (p < 0.05). Microcystin-degrading Microbacterium, Bacillus, Pseudomonas, and Acinetobacter were the dominant bacteria in the gut microbiota.

Conclusion: These results suggested that exposure to different concentrations of microcystin-LR caused changes in the gut microbiota, potentially affecting the metabolism of microcystin-LR, and ultimately impacting the toxicity of microcystin-LR in X. laevis development.

Keywords: Xenopus laevis; Gut microbiota; Intestinal development; Metamorphosis; Microcystin.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: The study was reviewed and approved by the Biological and Medical Ethics Committee of Qilu Normal University. Consent for publication: Not applicable. Competing interests: Lei Huang, and Hanping Pan are employees of Guangdong Meilikang Bio-Science Ltd., China. The rest of the authors declare to have no competing interest.

Figures

Fig. 1
Fig. 1
Framework showing the experimental design of the study
Fig. 2
Fig. 2
Intestinal microstructural changes of Xenopus laevis tadpoles exposed to different concentrations of microcystin-LR (MC-LR). “Second”, “Third”, and “Fourth” indicate the samples taken on stages 48, 57, and 62 of tadpole development, respectively. Blue arrows indicate the gap between the base and the villi. Numbers after the letter C in the group names indicate the MC-LR concentrations
Fig. 3
Fig. 3
Thickness of the intestinal epithelium in Xenopus laevis tadpoles. “Second”, “Third”,and “Fourth” indicate the samples taken on stages 48, 57, and 62 of tadpole development, respectively. Numbers after the letter C in the group names indicate the microcystin-LR (MC-LR) concentrations. Different letters above the bars indicate significant differences between groups (p < 0.05)
Fig. 4
Fig. 4
Changes in inflammatory factor gene expression levels in Xenopus laevis tadpole intestines after treatment with different microcystin-LR (MC-LR) concentrations. A TNF-α. B IL-8. CTGF-β. Numbers after the letter C in the group names indicate the MC-LR concentrations. Different letters above the bars indicate significant differences between groups (p < 0.05)
Fig. 5
Fig. 5
Changes in the gut microbiota composition of Xenopus laevis exposed to different microcystin-LR (MC-LR) concentrations. A–D Changes in alpha-diversity index values of X. laevis tadpole gut microbiota exposed to different concentrations of MC-LR. E Principal coordinate analysis (PCoA) profile of the gut microbiota composition. F PCoA profile of the gut microbiota composition grouped by sampling stages. G PCoA profile the gut microbiota composition grouped by MC-LR concentrations. H Weighted UniFrac distances of the gut microbiota between samples within and without groups. The samples were grouped according the sampling stages and MC-LR concentrations. ASTC, the distances across sampling times and MC-LR concentrations. Different lowercase letters at the above of the violin charts indicate that there are significant differences between groups. I Dominant phyla of the gut microbiota
Fig. 6
Fig. 6
The composition of dominant bacterial genera in the gut of Xenopus laevis tadpoles. A–D Represents the composition of dominant bacterial genera in the gut during the four sampling periods of tadpole development at 46, 48, 57, and 62 stages
Fig. 7
Fig. 7
Heatmap profile showing the genus composition
Fig. 8
Fig. 8
The dominant bacterial genera of Xenopus laevis tadpoles exposed to various concentrations of MC-LR showed significant differences compared to the control group. A–D, E–H, I–L, M–P represent the dominant bacterial genera with significant differences compared to the control group in the four treatment concentrations of 1, 5, 20, and 50 µg/L, respectively
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