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

Abstract

Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju (Ordem Nostocales) is one of the most troublesome bloom-forming species in Brazil. Understanding the population dynamics of the different morphotypes of C. raciborskii (straight and coiled) could assist in the prediction of favourable conditions for the proliferation of this potentially toxin-producing species. The aim of the present study was to assess the effects of two different light intensities and temperatures on the growth rate and morphology of the trichomes of the straight and coiled morphotypes. For such, two non-toxin producing strains of C. raciborskii were used -one with a coiled trichome (ITEP31) and another with a straight trichome (ITEP28). The strains were cultured in BG-11 medium in a climatic chamber under controlled conditions. Two light intensities (30 and 90 µmol.m -2 .s -1 ) were combined at temperatures of 21 and 31 °C and the growth rate and morphological changes were analysed. The morphotypes responded differently to the different temperatures and light intensities. Both strains exhibited faster growth velocities when submitted to higher light intensity and temperature. The lower temperature and higher luminosity hampered the development of both strains. Variations in cellular morphology and an absence of akinetes in both strains were related to the lower temperature (21 °C). The coiled morphotype demonstrated considerable phenotype plasticity, changing the morphology of trichome throughout its growth curve. Although molecular analysis does not sustain the separation of the morphotypes as distinct species, their different eco-physiological responses should be considered further knowledge of extreme importance for the population control of these potentially toxic organisms.Keywords: cyanobacteria, morphotype, growth curve, culture. Efeitos da intensidade luminosa e temperatura em Cylindrospermopsis raciborskii(Cyanobacteria) com tricomas retos e espiralados: taxa de crescimento e morfologia ResumoCylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju (Ordem Nostocales) é uma das espécies formadoras de florações mais prejudiciais no Brasil. Entender a dinâmica populacional dos diferentes morfotipos de C. raciborskii (reto e espiralado) pode auxiliar a previsão de condições favoráveis à proliferação e ao estabelecimento dessa espécie potencialmente produtora de saxitoxinas e cilindrospermopsina. O objetivo deste estudo foi avaliar os efeitos de duas diferentes intensidades luminosas e temperaturas na velocidade de crescimento e na morfologia dos tricomas de morfotipos reto e espiralado. Para tanto, foram utilizadas duas linhagens de C. raciborskii, não produtoras de toxinas, sendo uma com tricoma espiralado (ITEP31) e outra com tricoma reto (ITEP28), cultivadas em câmaras climáticas sob condições controladas em meio BG-11. Duas intensidades luminosas, 30 e 90 µmol.m -2 .s -1 , foram BIOLOGYBraz.

Photosynthetic characteristics of two Cylindrospermopsis raciborskii strains differing in their toxicity

“…However, in Brazilian strains, maximum growth rate was found to be higher for a straight trichome strain than for a coiled trichome strain (Bittencourt‐Oliveira et al. ). Despite having a higher μ c , CS506 reached a lower final cell concentration in stationary phase than did CS509.…”

Morpho-physiological responses of a subtropical strain of Cylindrospermopsis raciborskii (Cyanobacteria) to different light intensities

“…Most of the studies investigating the factors responsible for changes in morphology of C. raciborskii tested temperature (Chonudomkul et al 2004) or nutrients (Saker & Neilan 2001;Shafik et al 2003). On the other hand, only a few papers aimed to verify the influence of light intensity on trichomes (Bittencourt-Oliveira et al 2012;Bonilla et al 2012;Beamud et al 2016).…”

Constitutive toxin production under various nitrogen and phosphorus regimes of three ecotypes of Cylindrospermopsis raciborskii ((Wołoszyńska) Seenayya et Subba Raju)

“…The presence of multiple ecotypes, with differing Q CYN , which vary in dominance due to a range of poorly understood environmental drivers makes prediction of CYN concentrations during a bloom difficult (e.g. Bittencourt-Oliveira et al, 2012;Fathalli et al, 2011;Burford et al, 2014).…”