Morphology, genetic diversity, temperature tolerance and toxicity of Cylindrospermopsis raciborskii (Nostocales, Cyanobacteria) strains from Thailand and Japan

Abstract

Cylindrospermopsis raciborskii is a planktonic, nostocalean cyanobacterium, which produces an alkaloid heptatoxin, cylindrospermopsin. We performed morphological observations, 16S rDNA sequence analysis, PCR fingerprint analysis of short tandemly repeated repetitive (STRR) sequences, temperature tolerances and toxin analysis to characterize 24 strains of this toxic cyanobacterium isolated from Thailand and Japan. All strains shared common morphological traits characteristic of C. raciborskii and showed high 16S rDNA sequence similarity, forming a defined cluster together with the reference strains from Australia. In particular, some of the Thai strains shared 99.9% to 100% similarity with the Australian strains. Various combinations of STRR primers revealed different and unique DNA band patterns among strains of C. raciborskii. The phylogenetic tree revealed two main clusters of C. raciborskii strains, the Thai/Japan-Shinobazugaike cluster (cluster I) and the Japan-Gonoike cluster (cluster II). Cluster I was further divided into two subclusters, A (only Thai strains) and B (one Thai strain and the Japan-Shinobazugaike strains). Thus, the results from 16S rDNA and STRR analyses showed no clear geographical distinction between Japanese and Thai strains and between Thai and Australian strains. Thai strains were separated into adaptive and non-adaptive groups to low temperature (15 and 17.5 degrees C) and Japanese strains were composed of only low-temperature-adaptive ones. The toxin cylindrospermopsin was detected in some strains of cluster I-A and in one strain of cluster II. We conclude that C. raciborskii is a species that has recently begun to invade, and a species with different physiological strains or ecotypes in temperature tolerance; the toxin is synthesized without any relation to phylogenetic or genetic clusters and to geography.

Effects of light intensity and temperature on Cylindrospermopsis raciborskii (Cyanobacteria) with straight and coiled trichomes: growth rate and morphology

“…The molecular analysis indicated that both morphotypes belong to the same species, corroborating previous studies employing different molecular markers in C. raciborskii (Saker et al, 1999;Wilson et al, 2000;Dyble et al, 2002;Chonudonkul et al, 2004). The extreme phenotype plasticity of C. raciborskii is reported by a number of authors and is related to both biotic and abiotic factors (Bouvy et al, 1999;Komarková et al, 1999;Shafik et al, 2003).…”

“…This taxon exhibits extensive phenotype plasticity, with straight, sigmoid and coiled trichomes occurring in the same body of water (Bouvy et al, 1999;Komarková et al, 1999). Molecular studies have indicated that the different morphotypes of C. raciborskii should be considered as pertaining to the same species due to the high degree of genetic similarity (Saker et al, 1999;Wilson et al, 2000;Dyble et al, 2002;Chonudonkul et al, 2004).…”

Constitutive Cylindrospermopsin Pool Size in Cylindrospermopsis raciborskii under Different Light and CO 2 Partial Pressure Conditions

“…We also showed that differences in the transcription level of cyrA under different light intensities, and cyrK under different CO 2 conditions, have no control over the rates and timing of CYN pool size production. We therefore conclude that due to the constitutive nature of CYN pool size, the toxicity of a C. raciborskii bloom is likely to be controlled by population dynamics and strain-specific susceptibilities of strains (with different CYN cell quotas) to environmental parameters (21,33,(50)(51)(52)(53)(54)(55)(56) rather than by any direct stimulation of the CYN production pathway, including gene transcription. C. raciborskii bloom toxicity would also be governed by changes in light and CO 2 , which regulate the growth of (toxic) cells in the water column and the faster buildup of a (toxic) population, rather than by their effects on CYN pool size.…”

Thermal-dependent growth characteristics for Cylindrospermopsis raciborskii (Cyanoprokaryota) at different light availabilities: methodological considerations

“…To date, there are no such data available in the literature concerning Cylindrospermopsis raciborskii. Some authors investigated the temperature effect at a single (fixed) irradiance and the influence of irradiance at a single (fixed) temperature for growth of strains of C. raciborskii originating from diverse areas (Shaker et al 1999;Shafik et al 2001;Briand et al 2004, Chonudomkul et al 2004Piccini et al 2011). However, the interaction of the range of light and temperature conditions on the growth of this invasive species is not described.…”