Diversity of the Potential 2-Methylisoborneol-Producing Genotypes in Thai Strains of Planktothricoides (Cyanobacteria)

ABSTRACT The genus Planktothricoides Suda & Watanabe is considered as a 2-methylisoborneol (MIB) producer, affecting water quality and aquatic animal products worldwide. To date, there is limited information about the diversity of this genus from Thailand. In this study, Thai Planktothricoides strains were isolated from fish ponds and reservoirs in North, Northeast and Central regions for morphological examination, phylogenetic analyses based on 16S rRNA, rbcLX and MIB synthase genes as well as GC/MS/MS analyses. The morphological results and the 16S rRNA and rbcLX phylogenies of Thai Planktothricodes strains enabled them to be designated as Planktothricoides raciborskii. Cell dimensions of Thai strains tested were in 1.86 to 5.96 µm length (L), 2.83 to 13.70 µm width (W), and the L/W ratio ranged from 1:6 to 1:1. Among Planktothricoides strains, the 16S rRNA phylogenies demonstrated that three subclades (A, B and C groups) were apparently divided. The similarity of 16S rRNA genes between subclades were 96-98%. From the detection of MIB synthase genes and GC/MS/MS analyses, some strains grouped into A group were considered as MIB-producers. In this study, most Thai Planktothricoides strains belonging to the A group were found in all three regions, while the strains forming the B and C groups were not distributed in the North region. To our knowledge, the present study is the first report investigation and characterization of the potential MIB-producing Planktothricoides from Thailand. Therefore, providing a valuable tool as a model for the early prediction and detection of taste and odor event is necessary.