Green algae are fast-growing microorganisms that are considered promising for the production of starch and neutral lipids, and the chlorococcal green alga Parachlorella kessleri is a favorable model, as it can produce both starch and neutral lipids. P. kessleri commonly divides into more than two daughter cells by a specific mechanism-multiple fission. Here, we used synchronized cultures of the alga to study the effects of supra-optimal temperature. Synchronized cultures were grown at optimal (30 °C) and supra-optimal (40 °C) temperatures and incident light intensities of 110 and 500 μmol photons m-2 s-1. The time course of cell reproduction (DNA replication, cellular division), growth (total RNA, protein, cell dry matter, cell size), and synthesis of energy reserves (net starch, neutral lipid) was studied. At 40 °C, cell reproduction was arrested, but growth and accumulation of energy reserves continued; this led to the production of giant cells enriched in protein, starch, and neutral lipids. Furthermore, we examined whether the increased temperature could alleviate the effects of deuterated water on Parachlorella kessleri growth and division; results show that supra-optimal temperature can be used in algal biotechnology for the production of protein, (deuterated) starch, and neutral lipids.

• Klíčová slova
• Parachlorella kessleri, cell cycle, deuterated lipid, deuterated starch, deuterium, energy reserves, growth processes, microalgae, reproduction events, starch, supra-optimal temperature,
• MeSH
• biomasa MeSH
• buněčné dělení fyziologie   MeSH
• Chlorophyta růst a vývoj   MeSH
• lipidy MeSH
• metabolismus lipidů fyziologie   MeSH
• mikrořasy metabolismus   MeSH
• škrob metabolismus   MeSH
• teplota * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• lipidy MeSH
• škrob MeSH

Multiple fission is a cell cycle variation leading to the production of more than two daughter cells. Here, we used synchronized cultures of the chlorococcal green alga Parachlorella kessleri to study its growth and pattern of cell division under varying light intensities. The time courses of DNA replication, nuclear and cellular division, cell size, total RNA, protein content, dry matter and accumulation of starch were observed at incident light intensities of 110, 250 and 500 µmol photons m-2s-1. Furthermore, we studied the effect of deuterated water on Parachlorella kessleri growth and division, to mimic the effect of stress. We describe a novel multiple fission cell cycle pattern characterized by multiple rounds of DNA replication leading to cell polyploidization. Once completed, multiple nuclear divisions were performed with each of them, immediately followed by protoplast fission, terminated by the formation of daughter cells. The multiple fission cell cycle was represented by several consecutive doublings of growth parameters, each leading to the start of a reproductive sequence. The number of growth doublings increased with increasing light intensity and led to division into more daughter cells. This study establishes the baseline for cell cycle research at the molecular level as well as for potential biotechnological applications, particularly directed synthesis of (deuterated) starch and/or neutral lipids as carbon and energy reserves.

• Klíčová slova
• Parachlorella kessleri, cell cycle pattern, deuterated lipid, deuterated starch, deuterium, energy reserves, growth processes, light intensity, reproduction events,
• MeSH
• buněčné kultury * MeSH
• buněčný cyklus * MeSH
• Chlorophyta růst a vývoj   MeSH
• světlo * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Photosynthetic energy conversion and the resulting photoautotrophic growth of green algae can only occur in daylight, but DNA replication, nuclear and cellular divisions occur often during the night. With such a light/dark regime, an algal culture becomes synchronized. In this study, using synchronized cultures of the green alga Desmodesmus quadricauda, the dynamics of starch, lipid, polyphosphate, and guanine pools were investigated during the cell cycle by two independent methodologies; conventional biochemical analyzes of cell suspensions and confocal Raman microscopy of single algal cells. Raman microscopy reports not only on mean concentrations, but also on the distribution of pools within cells. This is more sensitive in detecting lipids than biochemical analysis, but both methods-as well as conventional fluorescence microscopy-were comparable in detecting polyphosphates. Discrepancies in the detection of starch by Raman microscopy are discussed. The power of Raman microscopy was proven to be particularly valuable in the detection of guanine, which was traceable by its unique vibrational signature. Guanine microcrystals occurred specifically at around the time of DNA replication and prior to nuclear division. Interestingly, guanine crystals co-localized with polyphosphates in the vicinity of nuclei around the time of nuclear division.

• Klíčová slova
• Desmodesmus quadricauda, cell cycle, confocal Raman microscopy, guanine, lipids, microalgae, polyphosphate, starch,
• MeSH
• buněčná stěna chemie   MeSH
• buněčný cyklus * MeSH
• časové faktory MeSH
• Chlorophyta cytologie   růst a vývoj   MeSH
• guanin analýza   MeSH
• lipidová tělíska metabolismus   MeSH
• lipidy analýza   MeSH
• mikroskopie * MeSH
• polyfosfáty analýza   MeSH
• Ramanova spektroskopie * MeSH
• škrob analýza   MeSH
• velikost buňky MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• guanin MeSH
• lipidy MeSH
• polyfosfáty MeSH
• škrob MeSH

Melting snow fields populated by aplanozygotes of the genus Chloromonas (Chlamydomonadales, Chlorophyta) are found in polar and alpine habitats. In the High Tatra Mountains (Slovakia), cells causing blooms of brownish-red snow designated as Scotiella tatrae kol turned out to be genetically (18S, ITS1 and ITS2 rDNA, rbcL) very closely related to Chloromonas nivalis (Chodat) Hoham et Mullet from the Austrian Alps. Therefore, Sc. tatrae is transferred into the latter taxon and reduced to a subspecies as Cr. nivalis subsp. tatrae. Both exhibit a similar photosynthetic performance, thrive in similar habitats at open sites above timberline, but differ in astaxanthin accumulation and number of aplanozygote cell wall flanges. In a field sample of Cr. nivalis subsp. tatrae, polyunsaturated fatty acids formed nearly 50 % of total lipids, dominating in phospholipids and glycolipids. Cr. nivalis subsp. tatrae represents likely a variation of a common cryoflora species with distinct morphology.

• Klíčová slova
• Chloromonas nivalis, High Tatra Mountains, Scotiella, aplanozygote, astaxanthin, fatty acids, field sample, photosynthesis, snow algae, ultrastructure,
• Publikační typ
• časopisecké články MeSH