Microcystis genotypes in a tropical freshwater lake: Discovery of novel MIB-producing Microcystis with potentially unique synthesis pathway

Kwan Chien Goh; Zhi Yang Sim; Shu Harn Te; Yiliang He; Karina Yew-Hoong Gin

doi:10.1016/j.scitotenv.2023.169249

Microcystis genotypes in a tropical freshwater lake: Discovery of novel MIB-producing Microcystis with potentially unique synthesis pathway

Sci Total Environ. 2024 Feb 20:912:169249. doi: 10.1016/j.scitotenv.2023.169249. Epub 2023 Dec 9.

Authors

Kwan Chien Goh¹, Zhi Yang Sim¹, Shu Harn Te¹, Yiliang He², Karina Yew-Hoong Gin³

Affiliations

¹ National University of Singapore Environmental Research Institute, National University of Singapore, 1 Create Way, #15-02, Singapore 138602, Singapore.
² School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
³ National University of Singapore Environmental Research Institute, National University of Singapore, 1 Create Way, #15-02, Singapore 138602, Singapore; Department of Civil and Environmental Engineering, National University of Singapore, Blk E1A-07-03, 1 Engineering Drive 2, Singapore 117576, Singapore. Electronic address: ceeginyh@nus.edu.sg.

PMID: 38081424
DOI: 10.1016/j.scitotenv.2023.169249

Abstract

Harmful algal blooms (HABs) are a threat to freshwater systems over the world due to the production of hepatotoxins like microcystin (MC), and nuisance taste and odour (T&O) compounds like 2-methylisoborneol (MIB). While MCs are known to cause detrimental effects to both water quality and human health, MIB is only reported to cause aesthetical problems. In this study, we investigated a tropical, urban lake that was experiencing persistent MC and MIB events. Although it was dominated by Microcystis blooms, analysis revealed that the toxigenic Microcystis were not the only species driving the MC concentrations. Additionally, there was also a lack of causative species for the MIB events. Through isolation, we have identified three toxigenic Microcystis found to produce four different variants of MCs, and two novel non-toxigenic Microcystis that were capable of producing MIB. The ability to produce MIB had never been previously reported for this species. Compared to other major producers such as Planktothricoides sp. and Streptomyces sp., the MIB synthase genes of our Microcystis sp. strains were partial, illustrating the possibility of unique synthesis pathways. The Microcystis sp. strains were found to produce about 2.77-5.22 fg MIB cell^-1, with a majority of the contents (70-80 %) existing in the extracellular phase. Correlation analysis of field study indicated that phosphorus limitation may have an indirect effect on non-toxigenic Microcystis abundance and proportion by influencing the toxigenic genotype, suggesting that current measures to control HABs may favour the proliferation of the non-toxigenic Microcystis. The potential for Microcystis sp. to produce MIB through unique synthesis pathway, coupled with the potential dominance of non-toxigenic genotypes in Microcystis blooms, signals the possibility that non-toxigenic Microcystis should be monitored as well.

Keywords: 2-Methylisoborneol; Cyanobacteria; Harmful algal bloom; Microcystin; Microcystis; Taste and odour.

MeSH terms

Cyanobacteria* / genetics
Genotype
Harmful Algal Bloom
Humans
Lakes / analysis
Microcystins / analysis
Microcystis* / genetics
Microcystis* / metabolism

Substances

Microcystins