Interspecific variation in extracellular polysaccharide content and colony formation of Microcystis spp. cultured under different light intensities and temperatures

Abstract

Single cells of five different Microcystis species (M. ichthyoblabe, M. viridis, M. flos-aquae, M. wesenbergii, and M. aeruginosa) were batch-cultured at different temperatures and light intensities: (a) 25°C and 50 μmol photons m −2 s −1 (control culture); (b) 25°C and 10 μmol p h o t o n s m − 2 s − 1 ; a n d ( c ) 1 5°C a n d 5 0 μ m o l photons m −2 s −1 . The extracellular polysaccharide content was significantly higher in treatments b and c than in the control treatment. All Microcystis species existed as single cells under the control treatment but formed colonies in treatments b and c. All of the colonies were irregular with indistinct margins. M. ichthyoblabe, M. viridis, M. flos-aquae, and M. wesenbergii formed colonies with similar morphologies and their cells were loosely aggregated. In contrast, M. aeruginosa formed denser colonies with no distinct holes.The colony morphologies differed from the classic morphology of M. ichthyoblabe field-grown colonies but resembled that of small colonies found in Lake Taihu (Yangtze Delta Plain, China) during early spring. This indicates that fieldand laboratory-grown colonies are governed by similar formation processes. We suggest that in laboratory and field environments, M. ichthyoblabe (or M. flos-aquae) colonies are representative of small colonies formed from single Microcystis cells, whereas the morphology of older colonies evolves to resemble M. wesenbergii and M. aeruginosa colonies.

Species-dependent variation in sensitivity of Microcystis species to copper sulfate: implication in algal toxicity of copper and controls of blooms

“…suggested that EPS is an important strategy to reduce Cu 2+ damage because –COO − and some amino groups in EPS can absorb heavy metals effectively48. Xu et al 49. demonstrated that EPS content was significantly lower in M. wesenbergii than the other three Microcystis species under standard culture conditions similar to ours.…”

Colony formation in the cyanobacterium Microcystis

“…Xu et al . () induced colony formation from single cells of five Microcystis species at a low temperature of 15°C; their colonies had similar morphologies but differed from most morphologies observed in the field. However, their induced colonies were similar to small unidentified colonies recorded in Lake Taihu (China) during early spring (Fig.…”

“…White arrows point to the visible margin that is filled with mucilage. A–C and E are from Xu et al (), D was provided by Junyi Zhang, and F was provided by Ming Li.…”

“…Some abiotic factors have also been reported to induce colony formation in Microcystis . Under a low temperature of 15°C and a low light intensity (10 µmol photons m −2 s −1 ), Microcystis cells form colonies of up to 100 µm in diameter (Li et al, ; Xu et al, ). Higher light intensities led to a faster growth rate of cells, accelerating the consumption of intracellular polysaccharides and other substances, decreasing the propensity to form colonies.…”

“…Extracellular polysaccharides (EPs) are key components in Microcystis colony formation (Li et al, ; Yang et al, ), with bEPs present surrounding the cells and soluble EPs (sEPs) secreted into the surrounding media (Yang et al, ). In field samples, colony size is correlated with bEPs levels, suggesting that extra bEPs may be secreted once colonies have formed (Li et al, ; Xu et al, ). Increased bEPs levels in laboratory cultures induced colony formation, while adding sEPs did not (Sato et al, ), reflecting the variable roles and compositions of these two different forms of EPs (Pereira et al, ).…”