Varied Diazotrophies, Morphologies, and Toxicities of Genetically Similar Isolates of Cylindrospermopsis raciborskii (Nostocales, Cyanophyceae) from Northern Australia

Abstract

The potentially toxic freshwater cyanobacterium Cylindrospermopsis raciborskii has become increasingly prevalent in tropical and temperate water bodies worldwide. This paper investigates the effects of different nitrogen sources (NO 3 ؊ , NH 4 ؉ , and omission of a fixed form of nitrogen) on the growth rates, morphologies, and cylindrospermopsin ( ؉ and the statistically significant increase in vegetative cell length (nitrogen depleted < NO 3 ؊ < NH 4 ؉ ). The morphological changes induced by different nitrogen sources were consistent for all isolates, despite measurable differences in vegetative-cell and heterocyst dimensions among isolates. Such induced morphological variation has implications for Cylindrospermopsis taxonomy, given that distinctions between species are based on minor and overlapping differences in cell lengths and widths. The close phylogenetic association among all seven isolates was confirmed by the high level (>99.8%) of similarity of their 16S rRNA gene sequences. Another genetic technique, analysis of the HIP1 octameric-palindrome repeated sequence, showed greater heterogeneity among the isolates and appears to be a useful method for distinguishing among isolates of C. raciborskii.

Initial growth phases of two bloom-forming cyanobacteria (Cylindrospermopsis raciborskiiandPlanktothrix agardhii) in monocultures and mixed cultures depending on light and nutrient conditions

“…Our results showed that under N-source starvation, monocultures of P. agardhii were unable to grow when NH 4 + or NO 3 x was depleted (i.e., m max = 0), whereas the growth of C. raciborskii seemed unaffected under NH 4 + and/or NO 3 x depletion and low concentration. The growth curves (IVF) recorded here, tend to suggest that C. raciborskii had a higher affinity for NH 4 + , as previously reported in Saker and Neilan (2001) and Kokocinski et al (2010) and other studies, who found that C. raciborskii grew faster when N was supplied in the form of ammonia, followed by nitrate, and then urea. In contrast, P. agardhii exhibited a clear preference for NO 3…”

Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju(Cyanobacteria): variação semanal e relações com fatores ambientais em um reservatório eutrófico, São Paulo, SP, Brasil

“…Isto se deve ao fato do nitrogênio nunca ser limitante no lago, sobretudo o íon amônio (tabela 2) que é a forma preferencial de absorção do nitrogênio (Saker & Neilan 2001). Desta forma, não há necessidade de gastos energéticos para formação de heterocitos.…”

Diversity of cyanobacteria and cyanotoxins in Hartbeespoort Dam, South Africa

“…These findings raise the question of whether C. curvispora, R. curvata and R. mediterranea can be regarded as separate species or are most likely just rare morphotypes of C. raciborskii. Strains of Cylindrospermopsis and Raphidiopsis from Australia, Brazil, China, Japan and Thailand produce CYN, STXs or ATX (Hawkins et al 1997;Saker and Neilan 2001;Li et al 2001;Namikoshi et al 2003;Soto-Liebe et al 2010). However, all the Cylindrospermopsis and Raphidiopsis strains isolated from Hartbeespoort Dam tested negative for production of cyanotoxins and their encoding genes.…”