Alteration of cylindrospermopsin production in sulfate- or phosphate-starved cyanobacteriumAphanizomenon ovalisporum

Abstract

The effect of sulfate and phosphate deprivation on cell growth and cylindrospermopsin level was studied in Aphanizomenon ovalisporum ILC-164. Sulfate starvation induced a characteristic reduction of cylindrospermopsin pool size on the basis of cell number and unit of dry mass of culture. Phosphorous starvation of A. ovalisporum cultures induced a lesser reduction of cylindrospermopsin pool size. This divergence in the pool size of cylindrospermopsin may be the consequence of different growth rate. To show the metabolic changes concomitant with reduction of cylindrospermopsin pool size were obtained by measurement of ATP sulfurylase and alkaline phosphatase activity. The present study is the first concerning the cylindrospermopsin content under sulfate starvation and discusses it in relation to phosphorous starvation.

Impact of Nitrogen Sources on Gene Expression and Toxin Production in the Diazotroph Cylindrospermopsis raciborskii CS-505 and Non-Diazotroph Raphidiopsis brookii D9

“…Our results show a clear positive correlation of toxin production to cell growth under nitrate and urea growth for CS-505 (Figure 4A), both treatments which promoted growth. Similar results were shown earlier in C. raciborskii by Hawkins et al [44] where CYN production correlated with growth rate at exponential phase, in A. ovalisporum [29], and are well described for microcystin producers [13,14]. However, they are in contradiction with reports on Aphanizomenon spp.…”

“…Studies in A. ovalisporum have shown that starvation for sulfate and phosphorous (P) produced a reduction of the cellular CYN content [29] whereas N starvation did not affect CYN content and increasing light intensity resulted in a larger accumulation of CYN in the cells and in the medium [23]. Transcript levels of the CYN biosynthetic genes, aoaA and aoaC (equivalent to cyrA and cyrC of C. raciborskii ) decreased in the high light and N starvation experiments indicating that toxin production is regulated by additional mechanisms.…”

“…In a different study, A. ovalisporum N-starvation resulted in a reduction of the cellular CYN content while transcript levels of the CYN biosynthetic genes, aoaA and aoaC , decreased independently of the amount of toxin recorded [23]. Other abiotic factors such as temperature, light and phosphate concentration have shown to affect CYN production and release [24,25,26,27,28,29], but toxin gene expression or protein activity was reported only in one study [27]. …”

Dynamics of Cylindrospermopsin Production and Toxin Gene Expression in <i>Aphanizomenon ovalisporum</i>

“…This fact and the high N content in the CYN molecule suggest the influence of N metabolism in the synthesis of the toxin. In general, nutrients seem to modulate CYN production, since nitrogen depletion [15] [16], phosphate and sulphate starvations cause significant changes in the toxin production [17].…”

Sporadic Distribution and Distinctive Variations of Cylindrospermopsin Genes in Cyanobacterial Strains and Environmental Samples from Chinese Freshwater Bodies

“…However, the protein-DNA interaction has not been verified in other CYN-producing species. The effects of temperature, light, nitrogen, phosphate, and sulfate on CYN production are inconclusive because of uncertainties in strain dependence, the release of CYNs, heterocyst formation, and combined effects of multiple factors in different experimental conditions (43)(44)(45)(46)(47)(48)(49)(50)(51). Davis et al (51) highlighted the effects of the genetic diversity of CYN producers on the concentration and composition of CYNs in aquatic ecosystems.…”