Australian Rivers Institute, Griffith University, 170 Kessels Road, Nathan, Queensland 4111, Australia; School of Environment, Griffith University, 170 Kessels Road, Nathan, Queensland 4111, Australia.
Australian Rivers Institute, Griffith University, 170 Kessels Road, Nathan, Queensland 4111, Australia.
Harmful Algae. 2017 Feb;62:84-93. doi: 10.1016/j.hal.2016.12.008. Epub 2017 Jan 6.
Microcystis aeruginosa and Cylindrospermopsis raciborskii are two cyanobacterial species that dominate freshwaters globally. Multiple strains of each species with different physiology occur, however, many studies have focused only on one or two strains, limiting our understanding of both strain variation and characterisation of the species. Therefore, in this study we examined the variation in growth and morphology of multiple isolates of both species, isolated from two adjacent Australian reservoirs. Four M. aeruginosa strains (=isolates) (one colony-forming, three single-celled morphology) and eight C. raciborskii isolates (five with straight trichomes, three with coiled trichomes) were cultured individually in a factorial designed experiment with four light intensities (L: 10, 30, 50 and 100μmol photons ms) and two temperatures (T: 20 and 28°C). The specific growth rate (μ), cell volume, and final cell concentration was measured. The light attenuation coefficient (k), a measure of self-shading, was calculated. The results showed that the intraspecific variation was greater than the interspecific variation. The μ of all isolates of M. aeruginosa and C. raciborskii ranged from 0.16 to 0.55d and 0.15 to 0.70d, respectively. However, at a specific light and temperature the mean μ of all M. aeruginosa isolates and C. raciborskii isolates were similar. At the species level, M. aeruginosa had higher growth rates at higher light intensity but lower temperature (L100T20), while straight C. raciborskii had higher growth rates at lower light intensity but higher temperature (L50T28), and coiled C. raciborskii had higher growth rates at higher light intensity and higher temperature (L100T28). The final cell concentrations of M. aeruginosa were higher than C. raciborskii. However, C. raciborskii isolates had greater variation in μ, k and cell volume than M. aeruginosa. k varied with light and temperature, and decreased with surface-to-volume ratio within each species. k was lower for M. aeruginosa compared to C. raciborskii as expected based on cell size, but interestingly, C. raciborskii coiled isolates had lower k than the straight isolates suggesting lower effect of self-shading. This study highlights the extent of strain variation to environmental conditions and to species variability.
铜绿微囊藻和节旋藻是两种在全球淡水环境中占主导地位的蓝藻物种。然而，每种物种都存在具有不同生理特性的多个菌株，许多研究仅关注一两个菌株，这限制了我们对菌株变异和物种特征的理解。因此，在这项研究中，我们检查了从两个澳大利亚相邻水库分离的两种物种的多个分离株的生长和形态变化。四种铜绿微囊藻菌株（一种集落形成，三种单细胞形态）和八种节旋藻分离株（五种直毛藻，三种卷曲毛藻）在具有四个光照强度（L：10、30、50 和 100μmol 光子 ms）和两个温度（T：20 和 28°C）的因子设计实验中分别进行培养。测量了比特定生长率（μ）、细胞体积和最终细胞浓度。计算了光衰减系数（k），这是自我遮光的度量。结果表明，种内变异大于种间变异。所有铜绿微囊藻和节旋藻分离株的μ值范围分别为 0.16 至 0.55d 和 0.15 至 0.70d。然而，在特定的光照和温度下，所有铜绿微囊藻和节旋藻分离株的平均μ值相似。在种水平上，铜绿微囊藻在高光强但低温（L100T20）下生长速度较高，而直节旋藻在低光强但高温（L50T28）下生长速度较高，而卷曲节旋藻在高光强和高温（L100T28）下生长速度较高。铜绿微囊藻的最终细胞浓度高于节旋藻。然而，节旋藻分离株的μ、k 和细胞体积变化大于铜绿微囊藻。k 值随光照和温度而变化，并在每个物种内随表面积与体积比的增加而减小。基于细胞大小，铜绿微囊藻的 k 值低于节旋藻，这是意料之中的，但有趣的是，卷曲节旋藻的 k 值低于直节旋藻，这表明自我遮光的影响较低。这项研究强调了菌株对环境条件和物种变异性的适应程度。
