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SUMMARY: Correctly identifying species of Chlorella‐like microalgae is difficult because of their morphological simplicity and high phenotypic plasticity. The use of molecular tools has revolutionized research on algal diversity, enabling such advances as the discovery of numerous new taxa. This article presents the results of a study of strains that are newly isolated from a freshwater Lake Prudovikov (Samara region, Russian Federation). These strains had the typical Chlorella morphology, exhibiting spherical cells and a cup‐shaped parietal chloroplast. The chloroplast contained a single pyrenoid enveloped by starch grains. However, 18S–ITS1–5.8S–ITS2 sequence analyses indicated that the studied strains are strongly allied with the well‐supported genus Micractinium. Based on the results of a comparative analysis of the morphological, molecular and environmental characteristics of the studied strains (employing a polyphasic approach), we propose that they are new species of Micractinium: Micractinium kostikovii sp. nov. [ABSTRACT FROM AUTHOR]

We characterized the photoautotrophic growth of glucose-tolerant Synechocystis sp. PCC 6803 in a flat-panel photobioreactor running on a semicontinuous regime under various lights, temperatures, and influx carbon dioxide concentrations. The maximum reached growth rate was 0.135 h−1, which corresponds to a doubling time of 5.13 h-a growth speed never reported for Synechocystis before. Saturating red light intensity for the strain was 220-360 μmol(photons) m−2 s−1, and we did not observe any photoinhibition up to 660 μmol(photons) m−2 s−1. Synechocystis was able to grow under red light only; however, photons of wavelengths 405-585 and 670-700 nm further improved its growth. Optimal growth temperature was 35°C. Below 32°C, the growth rates decreased linearly with temperature coefficient ( Q10) 1.70. Semicontinuous cultivation is known to be efficient for growth characterization and optimization. However, the assumption of correct growth rates calculation-culture exponential growth-is often not fulfilled. The semicontinuous setup in this study was operated as a turbidostat. Accurate online OD measurements with high time-resolution allowed fast and reliable growth rates determination. Repeating diluting frequencies (up to 18 dilutions per day) were essential for rapid growth stability evaluation. The presented setup provides improvement to previously published semicontinuous characterization strategies by decreasing experimental time requirements and maintaining the culture in exponential growth phase throughout the entire characterization procedure. [ABSTRACT FROM AUTHOR]