Cell reproductive patterns in the green alga Pseudokirchneriella subcapitata (=Selenastrum capricornutum) and their variations under exposure to the typical toxicants potassium dichromate and 3,5-DCP

Abstract

Pseudokirchneriella subcapitata is a sickle-shaped freshwater green microalga that is normally found in unicellular form. Currently, it is the best known and most frequently used species of ecotoxicological bioindicator because of its high growth rate and sensitivity to toxicants. However, despite this organism’s, our knowledge of its cell biology—for example, the patterns of nuclear and cytoplasmic division in the mitotic stage—is limited. Although it has been reported that P. subcapitata proliferates by popularity forming four daughter cells (autospores) through multiple fission after two nuclear divisions, here, we report two additional reproductive patterns by which two autospores are formed by binary fission (“two-autospore type”) and eight autospores are formed by multiple fission (“eight-autospore type”). Moreover, we found that cell reproductive patterns differed markedly with the culture conditions or with exposure to either of two typical toxicants, potassium dichromate (K2Cr2O7) and 3,5-dichlorophenol (3,5-DCP). The eight-autospore type occurred at the highest frequency in the early phase of culture, but it disappeared under 3,5-DCP at 2.0 mg/L. Under 0.3 mg/L K2CrO7 (Cr(VI)) the eight-autospore type took substantially longer to appear than in control culture. The two-autospore type occurred only in the late phase of culture. To our knowledge, this is the first detailed evaluation of the reproductive patterns of P. subcapitata, which changed dramatically in the presence of toxicants. These findings suggest that observation of the reproductive patterns of P. subcapitata will help to elucidate different cell reactions to toxicants.

Small heat shock protein genes of the green algae Closterium ehrenbergii: Cloning and differential expression under heat and heavy metal stresses

“…The toxic effects of potassium dichromate on the photosynthesis were also investigated in five species of marine microalgae, and showed an overall sensitivity and decrease of the photosynthesis efficiency with increased time and concentration . Additionally, increasing concentration of potassium dichromate has shown to be inducing a general decline in cell densities in the green alga Pseudokirchneriella subcapitata . Moreover, recent study by Wang et al on the effect of copper on C. ehrenbergii showed that F v /F m was considerably affected by copper toxicity and also declined with increasing copper concentration and exposure time, indicating that chlorophyll content and/or photosynthetic electron transport might be inhibited by exposure to the metal …”

“…73 Additionally, increasing concentration of potassium dichromate has shown to be inducing a general decline in cell densities in the green alga Pseudokirchneriella subcapitata. 74 Moreover, showed that F v /F m was considerably affected by copper toxicity and also declined with increasing copper concentration and exposure time, indicating that chlorophyll content and/or photosynthetic electron transport might be inhibited by exposure to the metal. 35…”

Removal and Biodegradation of 17β-Estradiol and Diethylstilbestrol by the Freshwater Microalgae Raphidocelis subcapitata

“…Selenastrum capricornutum , Pseudokirchneriella subcapitata and Raphidocelis subcapitata are the same species named in different periods [ 25 ]. The species is a sickle-shaped and unicellular green microalga that is normally found in fresh water.…”

Raphidocelis subcapitata (=Pseudokirchneriella subcapitata) provides an insight into genome evolution and environmental adaptations in the Sphaeropleales

“…In the Sphaeropleales cell cycle, the stage with motility (e.g. flagellates) is not dominant or not known 60 , 61 . Immobility may force cells to adapt to different environmental conditions aided by their numerous transporters.…”