Red snow is a well-known phenomenon caused by microalgae thriving in alpine and polar regions during the melting season. The ecology and biodiversity of these organisms, which are adapted to low temperatures, high irradiance and freeze-thaw events, are still poorly understood. We compared two different snow habitats containing two different green algal genera in the European Alps, namely algae blooming in seasonal rock-based snowfields (Chlamydomonas nivalis) and algae dominating waterlogged snow bedded over ice (Chlainomonassp.). Despite the morphological similarity of the red spores found at the snow surface, we found differences in intracellular organization investigated by light and transmission electron microscopy and in secondary pigments investigated by chromatographic analysis in combination with mass spectrometry. Spores ofChlainomonassp. show clear differences fromChlamydomonas nivalisin cell wall arrangement and plastid organization. Active photosynthesis at ambient temperatures indicates a high physiological activity, despite no cell division being present. Lipid bodies containing the carotenoid astaxanthin, which produces the red color, dominate cells of both species, but are modified differently. While inChlainomonassp. astaxanthin is mainly esterified with two fatty acids and is more apolar, inChamydomonas nivalis, in contrast, less apolar monoesters prevail.
- Klíčová slova
- astaxanthin, cryoflora, snow algae, spores, ultrastructure,
- MeSH
- biologické pigmenty fyziologie MeSH
- buněčná stěna chemie ultrastruktura MeSH
- Chlamydomonas fyziologie ultrastruktura MeSH
- ekosystém MeSH
- fotosyntéza fyziologie MeSH
- hmotnostní spektrometrie MeSH
- nízká teplota MeSH
- roční období MeSH
- sníh mikrobiologie MeSH
- světlo MeSH
- xanthofyly fyziologie MeSH
- zmrazování MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
- Geografické názvy
- Evropa MeSH
- Názvy látek
- astaxanthine MeSH Prohlížeč
- biologické pigmenty MeSH
- xanthofyly MeSH
Differences in the level of cold acclimation and cryoprotection estimated as ice nucleation activity in snow algae (Chlamydomonas cf. nivalis and Chloromonas nivalis), lichen symbiotic algae (Trebouxia asymmetrica, Trebouxia erici and Trebouxia glomerata), and a mesophilic strain (Chlamydomonas reinhardti) were evaluated. Ice nucleation activity was measured using the freezing droplet method. Measurements were performed using suspensions of cells of A750 (absorbance at 750 nm) ~ 1, 0.1, 0.01 and 0.001 dilutions for each strain. The algae had lower ice nucleation activity, with the exception of Chloromonas nivalis contaminated by bacteria. The supercooling points of the snow algae were higher than those of lichen photobionts. The supercooling points of both, mesophilic and snow Chlamydomonas strains were similar. The lower freezing temperatures of the lichen algae may reflect either the more extreme and more variable environmental conditions of the original localities or the different cellular structure of the strains examined.
- MeSH
- aklimatizace MeSH
- Chlamydomonas chemie cytologie fyziologie MeSH
- Chlorophyta chemie cytologie fyziologie MeSH
- krystalizace MeSH
- led analýza MeSH
- lišejníky fyziologie MeSH
- symbióza MeSH
- zmrazování MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- led MeSH
A long-living artificial tripartite symbiosis involving a green alga (Chlamydomonas), a bacterium (Azotobacter) and a fungus (Alternaria) was established on carbon- and nitrogen-free medium. The basis of the interdependence is the complementation of photosynthetic CO2 assimilation and atmospheric nitrogen fixation. Green color of the colonies indicated that the algal cells had enough nitrogen to synthesize chlorophylls. The chlorophyll content was nearly 40% of the control cells. The relatively high rate of photosynthetic oxygen evolution proved that nitrogen was effectively used for building up a well functioning photosynthetic apparatus. This was supported by the analysis of photosystems and ultrastructural investigations. In comparison with degreened algae cultured on nitrogen-free medium, the chloroplasts in the symbiont algal cells contained a well-developed, stacked thylakoid membrane system without extreme starch or lipid accumulation. The occurrence of the fungus in the association greatly increased the chlorophyll content. Far fewer types of amino acids were excreted by the tripartite cultures than by pure cultures. Cystathionine, which is a common intermediate in the sulfur-containing amino acid metabolism, was produced in high quantities by the tripartite symbiosis. This can mostly be attributed to the activity of the fungus.
- MeSH
- Alternaria růst a vývoj metabolismus fyziologie MeSH
- aminokyseliny metabolismus MeSH
- Azotobacter růst a vývoj metabolismus fyziologie MeSH
- Chlamydomonas růst a vývoj metabolismus fyziologie ultrastruktura MeSH
- chlorofyl biosyntéza MeSH
- dusík metabolismus MeSH
- fixace dusíku MeSH
- fotosyntetické reakční centrum - proteinové komplexy analýza MeSH
- fotosyntéza MeSH
- kultivační média chemie MeSH
- lipidy analýza MeSH
- mikroskopie MeSH
- oxid uhličitý metabolismus MeSH
- škrob analýza MeSH
- symbióza * MeSH
- transmisní elektronová mikroskopie MeSH
- tylakoidy chemie ultrastruktura MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- aminokyseliny MeSH
- chlorofyl MeSH
- dusík MeSH
- fotosyntetické reakční centrum - proteinové komplexy MeSH
- kultivační média MeSH
- lipidy MeSH
- oxid uhličitý MeSH
- škrob MeSH
The seasonal and diel dynamics of the physiological state and photosynthetic activity of the snow alga Chlamydomonas nivalis were investigated in a snowfield in Svalbard. The snow surface represents an environment with very high irradiation intensities along with stable low temperatures close to freezing point. Photosynthetic activity was measured using pulse amplitude modulation fluorometry. Three types of cell (green biflagellate vegetative cells, orange spores clustered by means of mucilaginous sheaths, and purple spores with thick cell walls) were found, all of them photosynthetically active. The pH of snow ranged between 5.0 and 7.5, and the conductivity ranged between 5 and 75 microS cm(-1). The temperature of snow was stable (-0.1 to +0.1 degrees C), and the incident radiation values ranged from 11 to 1500 micromol photons m(-2) s(-1). The photosynthetic activity had seasonal and diel dynamics. The Fv/Fm values ranged between 0.4 and 0.7, and generally declined over the course of the season. A dynamic response of Fv/Fm to the irradiance was recorded. According to the saturating photon fluence values Ek, the algae may have obtained saturating light as deep as 3 cm in the snow when there were higher-light conditions, whereas they were undersaturated at prevalent low light even if on the surface.
- MeSH
- Chlamydomonas izolace a purifikace fyziologie MeSH
- fluorometrie metody MeSH
- fotosyntéza fyziologie MeSH
- roční období * MeSH
- sníh chemie mikrobiologie MeSH
- světlo MeSH
- tma MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Arktida MeSH
Three Chlamydomonas strains were isolated from the soils of a hot spring located in the Campi Flegrei Caldera (Naples, Italy). Ecophysiological, morpho-cytological and molecular features were used to characterize these isolates and to compare them with chlamydomonax acidophila strains from algal culture collections. The strains were collected from three points of the volcanic site, differing in their physico-chemical conditions. Among the examined Chlamydomonas strains, only the isolates from Campi Flegrei could grow optimally at pH values < or =3.0. These isolates also showed a high tolerance to desiccation and high temperatures, not evidenced by the other Chlamydomonas strains included in the study. 18S rDNA phylogeny indicates that the isolates from Campi Flegrei are closely related to Chlamydomonas pitschmannii and two strains isolated in Canada and Europe, that have been designated as Chlamydomonas acidophila. A Chlamydomonas acidophila strain isolated from the type locality in Japan is less closely related according to its molecular phylogeny, and can also be discerned by light and electron microscopy. Moreover, vegetative cells and sporangia of Chlamydomonas acidophila from Japan showed a median trilaminar structure not observed in the other strains. Our results show that Chlamydomonas pitschmannii could represent a hitherto unknown extremophilic Chlamydomonas species.
- MeSH
- buněčné dělení MeSH
- Chlamydomonas klasifikace cytologie genetika izolace a purifikace fyziologie MeSH
- Eukaryota parazitologie MeSH
- fylogeneze MeSH
- gametogeneze MeSH
- horké prameny parazitologie MeSH
- koncentrace vodíkových iontů MeSH
- molekulární sekvence - údaje MeSH
- půda parazitologie MeSH
- RNA ribozomální 18S genetika MeSH
- sekvenční analýza DNA MeSH
- sekvenční seřazení MeSH
- vakuoly ultrastruktura MeSH
- životní prostředí * MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
- Geografické názvy
- Česká republika MeSH
- Itálie MeSH
- Japonsko MeSH
- Kanada MeSH
- Názvy látek
- půda MeSH
- RNA ribozomální 18S MeSH
Routinely prepared gametes (by flooding 3 week-old agar cultures) showed about 80% mating competence if the opposite sexual partners were mixed together. The mating competence exhibited a strict dependence on the composition of the solution in which the cells were suspended before mixing; it decreased progressively with increasing concentration of nitrates. In contrast, no inhibiting effect was found if urea was used as the source of nitrogen. Other ions present in nutrient media did not show any effect. Mating activity varied according to the spectral composition of light, being higher with a blue light than with a red one. Blue light caused accumulation of vis-à-vis pairs, which were blocked to form zygotes. Freshly released daughter cells in vegetatively grown synchronous cultures had a dual nature--vegetative and sexual one. In these daughter cells, similar rules were found for governing of mating competence to those valid for standard gametes obtained from flooded agar cultures. High mating competence was found in daughter cells released the during dark period in distilled water, nitrate-free media, in the presence of Mg2+ or Ca2+ ions, or in media containing urea. The conditions during which daughter cells are released and the conditions under which they mate can be considered crucial for expression of gametic nature as a mating competence.
- MeSH
- Chlamydomonas růst a vývoj fyziologie MeSH
- dusičnany metabolismus MeSH
- kultivační média chemie MeSH
- močovina metabolismus MeSH
- rozmnožování fyziologie MeSH
- světlo * MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- dusičnany MeSH
- kultivační média MeSH
- močovina MeSH
