Author Contributions
Conceptualization, L.P., D.R., and L.N.; data curation, L.P.; formal analysis, L.P.; funding acquisition, D.R. and L.N.; investigation, L.P., D.R., and T.Ř.; methodology, L.P. and D.R.; project administration, D.R. and L.N.; resources, L.P., D.R., and L.N.; supervision, L.N.; visualization, L.P.; writing—original draft, L.P.; writing—review and editing, L.P. and D.R.
Figure 1.
Sampling locations of Chloromonas hindakii sp. nov. in (a) Krkonoše, Czech Republic (square), Jeseníky, Czech Republic (triangle), and at the High Tatras, Slovakia and Poland (circle), with codes of the European countries (AU, Austria; CZ, Czech Republic; DE, Germany; HU, Hungary; PL, Poland; SK, Slovakia); (b) Detailed map of the High Tatras, showing principal peaks with their elevation in meters (triangles).
Figure 1.
Sampling locations of Chloromonas hindakii sp. nov. in (a) Krkonoše, Czech Republic (square), Jeseníky, Czech Republic (triangle), and at the High Tatras, Slovakia and Poland (circle), with codes of the European countries (AU, Austria; CZ, Czech Republic; DE, Germany; HU, Hungary; PL, Poland; SK, Slovakia); (b) Detailed map of the High Tatras, showing principal peaks with their elevation in meters (triangles).
Figure 2.
Two representative sampling sites of Chloromonas hindakii indicated by red arrowheads and detailed views of the orange snow blooms. (a,c) Open site above timberline (i.e., high light conditions) in the High Tatra Mountains (sample WP194) and (b,d) semi-shaded site close to spruce trees (i.e., low light conditions) in the Krkonoše Mountains (sample DD2).
Figure 2.
Two representative sampling sites of Chloromonas hindakii indicated by red arrowheads and detailed views of the orange snow blooms. (a,c) Open site above timberline (i.e., high light conditions) in the High Tatra Mountains (sample WP194) and (b,d) semi-shaded site close to spruce trees (i.e., low light conditions) in the Krkonoše Mountains (sample DD2).
Figure 3.
Light and electron microscopy of field-collected cysts of Chloromonas hindakii sp. nov.—samples Jes 19-1 (a,b), WP129 (c,d), WP194 (e,f,h–k), and DD2 (g). (a–d) Light micrographs. (a) Surface view showing cell wall flanges. (b,c) Optical sections, showing cytoplasm containing reddish astaxanthin depots and greenish chloroplast (b) and prominent wall flanges reaching the cell apexes (c). (d) A cell in upright position, showing eight cell wall flanges. (e–g) Transmission electron micrographs. (e) Cell cross-section showing cleavages within the mother cell wall. (f) A detailed view of the newly formed cell wall of two daughter cells (empty arrowheads). (g) The cytoplasm of mature cysts occupied by large peripheral lipid bodies (l) with centrally located chloroplasts (c). (h–k) Scanning electron micrographs, showing characteristic organization of the cell ornamentation. An empty arrowhead indicates a flange reaching from pole to antapex. (h) Two flanges joining or a bifurcation of one flange into two independents (white arrowheads). (i) An isolated furcated flange (white arrowhead), (j) Slightly undulating flanges. (k) Apical view of a cell presenting eight flanges in total. Four of them are usually running from apex to antapex.
Figure 3.
Light and electron microscopy of field-collected cysts of Chloromonas hindakii sp. nov.—samples Jes 19-1 (a,b), WP129 (c,d), WP194 (e,f,h–k), and DD2 (g). (a–d) Light micrographs. (a) Surface view showing cell wall flanges. (b,c) Optical sections, showing cytoplasm containing reddish astaxanthin depots and greenish chloroplast (b) and prominent wall flanges reaching the cell apexes (c). (d) A cell in upright position, showing eight cell wall flanges. (e–g) Transmission electron micrographs. (e) Cell cross-section showing cleavages within the mother cell wall. (f) A detailed view of the newly formed cell wall of two daughter cells (empty arrowheads). (g) The cytoplasm of mature cysts occupied by large peripheral lipid bodies (l) with centrally located chloroplasts (c). (h–k) Scanning electron micrographs, showing characteristic organization of the cell ornamentation. An empty arrowhead indicates a flange reaching from pole to antapex. (h) Two flanges joining or a bifurcation of one flange into two independents (white arrowheads). (i) An isolated furcated flange (white arrowhead), (j) Slightly undulating flanges. (k) Apical view of a cell presenting eight flanges in total. Four of them are usually running from apex to antapex.
Figure 4.
18S ribosomal RNA gene-based Bayesian phylogenetic tree of
Chloromonas focusing on snow-inhabiting species.
C. =
Chloromonas. The labeled clades ‘A’, ‘B’, and ‘C’ correspond to [
4]. Posterior probabilities (0.95 or more) and bootstrap values from maximum likelihood analyses (50% or more) are shown. Full statistical support (1.00/100) is marked with an asterisk. Thick branches represent nodes receiving the highest posterior probability support (1.00). Newly obtained sequences are in bold. Accession numbers, strain, or field sample codes are indicated after each species name.
Figure 4.
18S ribosomal RNA gene-based Bayesian phylogenetic tree of
Chloromonas focusing on snow-inhabiting species.
C. =
Chloromonas. The labeled clades ‘A’, ‘B’, and ‘C’ correspond to [
4]. Posterior probabilities (0.95 or more) and bootstrap values from maximum likelihood analyses (50% or more) are shown. Full statistical support (1.00/100) is marked with an asterisk. Thick branches represent nodes receiving the highest posterior probability support (1.00). Newly obtained sequences are in bold. Accession numbers, strain, or field sample codes are indicated after each species name.
Figure 5.
rbcL gene-based Bayesian phylogenetic tree of
Chloromonas focusing on snow-inhabiting species.
C. =
Chloromonas. The labeled clades ‘A’, ‘B’, and ‘C’ correspond to [
4]. Posterior probabilities (0.95 or more) and bootstrap values from maximum likelihood analyses (50% or more) are shown. Full statistical support (1.00/100) is marked with an asterisk. Thick branches represent nodes receiving the highest posterior probability support (1.00). Newly obtained sequences are in bold. Accession numbers, strain, or field sample codes are indicated after each species name.
Figure 5.
rbcL gene-based Bayesian phylogenetic tree of
Chloromonas focusing on snow-inhabiting species.
C. =
Chloromonas. The labeled clades ‘A’, ‘B’, and ‘C’ correspond to [
4]. Posterior probabilities (0.95 or more) and bootstrap values from maximum likelihood analyses (50% or more) are shown. Full statistical support (1.00/100) is marked with an asterisk. Thick branches represent nodes receiving the highest posterior probability support (1.00). Newly obtained sequences are in bold. Accession numbers, strain, or field sample codes are indicated after each species name.
Figure 6.
Intraspecific variability in the secondary structure of ITS2 rDNA transcripts of Chloromonas hindakii sp. nov.—comparison between the type strain WP129 (= CCCryo 531-19) (accession number MN251865) and field-collected cysts from different localities. The marker was identical for the strain and the following field samples: Rozcestí (MN251867), Jes19-6 (MN251869), LP06 (MN251870), NW (MN251872), WP194 (MN251873). It differed by 1–4 bp in comparison with the field samples (1-DD2, MN251866; 2-Jes19-1, MN251868; 3-WP136, MN251871). Helices are labeled with Latin numbers: I–IV. Nucleotide differences of the field samples are described in red outside the structure and linked by dotted lines. Note the U–U mismatch in helix II (arrows).
Figure 6.
Intraspecific variability in the secondary structure of ITS2 rDNA transcripts of Chloromonas hindakii sp. nov.—comparison between the type strain WP129 (= CCCryo 531-19) (accession number MN251865) and field-collected cysts from different localities. The marker was identical for the strain and the following field samples: Rozcestí (MN251867), Jes19-6 (MN251869), LP06 (MN251870), NW (MN251872), WP194 (MN251873). It differed by 1–4 bp in comparison with the field samples (1-DD2, MN251866; 2-Jes19-1, MN251868; 3-WP136, MN251871). Helices are labeled with Latin numbers: I–IV. Nucleotide differences of the field samples are described in red outside the structure and linked by dotted lines. Note the U–U mismatch in helix II (arrows).
Figure 7.
LM and TEM of vegetative cells of Chloromonas hindakii sp. nov. strain WP129 (= CCCryo 531-19): (a–e) LM. (a) Optical section of the cell, showing two contractile vacuoles (white arrowheads) and a chloroplast not totally occupying the posterior end of the protoplast (black arrowhead) within the cell. (b) Position of the nucleus (white arrowhead) within the cell. (c) Sporangium and plate-like sections of the plastid. (d,e) Development of two spherical daughter cells. (f–k) TEM. The following structures are labeled: Undulating plasmatic membrane (arrowhead), chloroplast (c), endoplasmic reticulum (e), flagellum (f), Golgi body (g), mitochondrion (m), nucleus (n), starch (s), vacuole with crystalline content (v). (f) Longitudinal cell section, showing position of nucleus. (g) Papilla shape. (h) Cell cleavage. (i) Two spherical daughter cells in mother cell wall, still lacking own cell wall. (j) Detail of one out of four spherical daughter cells with newly developed cell wall, still inside the sporangium wall. Note prominent rough endoplasmic reticulum. (k) Transversal cell section of an older cell with many discoid chloroplasts including starch grains.
Figure 7.
LM and TEM of vegetative cells of Chloromonas hindakii sp. nov. strain WP129 (= CCCryo 531-19): (a–e) LM. (a) Optical section of the cell, showing two contractile vacuoles (white arrowheads) and a chloroplast not totally occupying the posterior end of the protoplast (black arrowhead) within the cell. (b) Position of the nucleus (white arrowhead) within the cell. (c) Sporangium and plate-like sections of the plastid. (d,e) Development of two spherical daughter cells. (f–k) TEM. The following structures are labeled: Undulating plasmatic membrane (arrowhead), chloroplast (c), endoplasmic reticulum (e), flagellum (f), Golgi body (g), mitochondrion (m), nucleus (n), starch (s), vacuole with crystalline content (v). (f) Longitudinal cell section, showing position of nucleus. (g) Papilla shape. (h) Cell cleavage. (i) Two spherical daughter cells in mother cell wall, still lacking own cell wall. (j) Detail of one out of four spherical daughter cells with newly developed cell wall, still inside the sporangium wall. Note prominent rough endoplasmic reticulum. (k) Transversal cell section of an older cell with many discoid chloroplasts including starch grains.
Figure 8.
Rapid light curves showing the intraspecific photosynthetic flexibility of
Chloromonas hindakii sp. nov. The effect of increasing photon fluence rates (x-axis) on the relative electron transport rate (rETR; y-axis) of chloroplasts was measured for vegetative flagellates (green diamonds, strain WP129 (= CCCryo 531-19) grown in the lab) and non-motile field-collected cysts (blue triangles—semi-shaded site close to a spruce canopy, sample DD2; orange circles—site above timberline, population located mainly 3–5 cm below snow surface, sample LP06; red boxes—site above timberline, population at snow surface, sample WP194). Values are means of four replicate measurements (
n = 4, ± SD). The data points were fitted to the photoinhibition model of [
46].
Figure 8.
Rapid light curves showing the intraspecific photosynthetic flexibility of
Chloromonas hindakii sp. nov. The effect of increasing photon fluence rates (x-axis) on the relative electron transport rate (rETR; y-axis) of chloroplasts was measured for vegetative flagellates (green diamonds, strain WP129 (= CCCryo 531-19) grown in the lab) and non-motile field-collected cysts (blue triangles—semi-shaded site close to a spruce canopy, sample DD2; orange circles—site above timberline, population located mainly 3–5 cm below snow surface, sample LP06; red boxes—site above timberline, population at snow surface, sample WP194). Values are means of four replicate measurements (
n = 4, ± SD). The data points were fitted to the photoinhibition model of [
46].
Table 1.
Sampling locations of
Chloromonas hindakii sp. nov. from Krkonoše, Jeseníky, and High (H.) Tatra Mountains with sample codes, collection date, sampling site, altitude (m a.s.l.) and geographic position (GPS) (CZ, Czech Republic; PL, Poland; SK, Slovakia). The numbers in parentheses indicate position in the map of
Figure 1 (L., Lake).
Table 1.
Sampling locations of
Chloromonas hindakii sp. nov. from Krkonoše, Jeseníky, and High (H.) Tatra Mountains with sample codes, collection date, sampling site, altitude (m a.s.l.) and geographic position (GPS) (CZ, Czech Republic; PL, Poland; SK, Slovakia). The numbers in parentheses indicate position in the map of
Figure 1 (L., Lake).
Sample | Date | Location | Altitude | GPS |
---|
DD2 | 11.5.2017 | CZ (1), Krkonoše, Dlouhý důl | 984 | N50°43.231 E15°39.433 |
Rozcestí | 12.5.2017 | CZ (2), Krkonoše, close to Na Rozcestí | 1349 | N50°42.327 E15°40.368 |
Jes19-1 | 8.5.2019 | CZ (3), Jeseníky, close to U Výrovky | 1137 | N50°06.673 E17°10.967 |
Jes19-6 | 9.5.2019 | CZ (4), Jeseníky, next to Sněžná kotlina | 1157 | N50°08.121 E17°08.817 |
LP06 | 14.6.2017 | PL (5), H. Tatras, Dolina za Mnichem | 1858 | N49°11.656 E20°03.146 |
WP129 | 15.6.2017 | PL (6), H. Tatras, Dolina za Mnichem | 2082 | N49°11.424 E20°03.153 |
WP130 | 15.6.2017 | PL (7), H.Tatras, ice-covered Zadni Mnichowy L. | 2038 | N49°11.403 E20°03.101 |
WP136 | 15.6.2017 | SK (8), H. Tatras, Mengusovská dolina | 1976 | N49°10.475 E20°04.910 |
NW | 18.6.2017 | SK (9), H. Tatras, shore of Nižné Wahlenberg.L. | 2061 | N49°9.543 E20°1.612 |
WP194 | 17.6.2018 | SK (10), H. Tatras, Velká Studená dolina | 2022 | N49°10.540 E20°09.414 |
Table 2.
List of primers used for amplification of 18S rDNA, ITS1 rDNA, ITS2 rDNA (ITS), and rbcL markers (F, forward; R, reverse).
Table 2.
List of primers used for amplification of 18S rDNA, ITS1 rDNA, ITS2 rDNA (ITS), and rbcL markers (F, forward; R, reverse).
Primer | Marker | Direction | Sequence | Reference |
---|
SSU | ITS2 | F | CTGCGGAAGGATCATTGATTC | [26] |
LSU | ITS2 | R | AGTTCAGCGGGTGGTCTTG | [26] |
ITS5 | ITS2 | F | GGAAGTAAAAGTCGTAACAAGG | [27] |
ITS1 | ITS2 | F | TCCGTAGGTGAACCTGCGG | [27] |
ITS4 | ITS2 | R | TCCTCCGCTTATTGATATGC | [27] |
Al1500af | ITS2 | F | GCGCGCTACACTGATGC | [28] |
LR3 | ITS2 | R | GGTCCGTGTTTCAAGACGG | [29] |
18F2 | 18S | F | AACCTGGTTGATCCTGCCAGT | [30] |
18R2 | 18S | R | TGATCCTTCTGCAGGTTCACCTACG | [30] |
rbcL1F | rbcL | F | CTGCTTTATACTGCGAAACTGC | [31] |
rbcL7R | rbcL | R | AAATAAATACCACGGCTACG | [31] |
Table 3.
List of marker sequences for the authentic strain of Chloromonas hindakii and field samples, indicating the Genbank accession numbers for ITS2 rDNA/18S rDNA/rbcL sequences.
Table 3.
List of marker sequences for the authentic strain of Chloromonas hindakii and field samples, indicating the Genbank accession numbers for ITS2 rDNA/18S rDNA/rbcL sequences.
Sample/Strain Code | NCBI Accession Numbers |
---|
ITS2 rDNA | 18S rDNA | rbcL |
---|
WP129 (= CCCryo 531-19) | MN251865 | MN251865 | MN251877 |
DD2 | MN251866 | MN251874 | MN251878 |
Rozcestí | MN251867 | MN251875 | MN251879 |
Jes19-1 | MN251868 | | |
Jes19-6 | MN251869 | MN251876 | |
LP06 | MN251870 | | |
WP136 | MN251871 | | |
NW | MN251872 | | MN251880 |
WP194 | MN251873 | | MN251881 |
Table 4.
Abiotic habitat parameters and cell sizes of Chloromonas hindakii field samples from the Krkonoše, Jeseníky, and High Tatra Mountains. Electrical conductivity (EC; μS.cm−1), pH of meltwater and snow water content (SWE; %), maximal population density ± standard deviation (SD), average sizes of cells in μm ± SD, length to width ratio (L:W ratio) ± SD are shown.
Table 4.
Abiotic habitat parameters and cell sizes of Chloromonas hindakii field samples from the Krkonoše, Jeseníky, and High Tatra Mountains. Electrical conductivity (EC; μS.cm−1), pH of meltwater and snow water content (SWE; %), maximal population density ± standard deviation (SD), average sizes of cells in μm ± SD, length to width ratio (L:W ratio) ± SD are shown.
Sample | EC | pH | SWE | Cells Per mL Meltwater | Cell Length | Cell Width | L:W Ratio |
---|
DD2 | 14 | 5.7 | 48.7 ± 0.3 | 19,950 ± 2000 | 25.5 ± 2 | 16.3 ± 1.4 | 1.57 ± 0.1 |
Rozcestí | 9 | 5.9 | - | - | 25.0 ± 2.1 | 16.6 ± 1.5 | 1.51 ± 0.1 |
Jes19-1 | 28 | 7.0 | - | 60,800 ± 6080 | 27.3 ± 2.1 | 17.9 ± 2.2 | 1.53 ± 0.1 |
Jes19-6 | 33 | 6.9 | - | 43,050 ± 4300 | 30.3 ± 2.1 | 19.7 ± 1.7 | 1.54 ± 0.1 |
LP06 | 5.2 | 5.5 | 55.9 ± 2.1 | 54,150 ± 5400 | 25.2 ± 2 | 16.4 ± 1.5 | 1.54 ± 0.1 |
WP129 | - | - | - | - | 23.7 ± 1.2 | 15.0 ± 0.8 | 1.52 ± 0.1 |
WP130 | - | - | - | 47,100 ± 4700 | - | - | - |
WP136 | - | - | - | 79,100 ± 7900 | 23.5 ± 2.3 | 15.6 ± 2.1 | 1.52 ± 0.1 |
NW | - | - | - | - | 23.0 ± 2.1 | 15.0 ±1.4 | 1.54 ± 0.1 |
WP194 | 5.1 | 6.8 | 60.8 ± 5.97 | 21,900 ± 2100 | 26.8 ± 1.4 | 17.6 ± 1.4 | 1.53 ± 0.1 |
Table 5.
Relative cellular content of carotenoids, chlorophyll b, and α-tocopherol in relation to chlorophyll a (= 1) in field samples of Chloromonas hindakii sp. nov. from the High Tatras at the Slovak side (sample WP194; high light conditions) and at the Polish side (LP06; low light conditions), determined by HPLC. Abbreviations: n & v, neoxanthin and violaxanthin; lut, lutein; zea, zeaxanthin; chl b, chlorophyll b; β-car, β-carotene; ast, astaxanthin (free/unesterified); ast-E, astaxanthin derivatives (esters); ast-tot, astaxanthin in total (free and derivatives); α-toc; α-tocopherol; n.d., not detected.
Table 5.
Relative cellular content of carotenoids, chlorophyll b, and α-tocopherol in relation to chlorophyll a (= 1) in field samples of Chloromonas hindakii sp. nov. from the High Tatras at the Slovak side (sample WP194; high light conditions) and at the Polish side (LP06; low light conditions), determined by HPLC. Abbreviations: n & v, neoxanthin and violaxanthin; lut, lutein; zea, zeaxanthin; chl b, chlorophyll b; β-car, β-carotene; ast, astaxanthin (free/unesterified); ast-E, astaxanthin derivatives (esters); ast-tot, astaxanthin in total (free and derivatives); α-toc; α-tocopherol; n.d., not detected.
Sample | N&V | Lut | Zea | Chl b | β-car | Ast | Ast-E | Ast-tot | α-toc |
---|
WP194 | 0.120 | 0.315 | n.d. | 0.227 | 0.014 | 0.037 | 0.385 | 0.422 | 0.085 |
LP06 | 0.135 | 0.277 | n.d. | 0.273 | 0.020 | 0.012 | 0.476 | 0.488 | 0.080 |
Table 6.
Cellular fatty acid composition of Chloromonas hindakii sp. nov. vegetative strain WP129 (= CCCryo 531-19) cultivated at 1 °C (n = 3) compared to field-collected cysts (from sample Rozcestí) in % of total lipids (TL) and in % of the three major lipid groups: Neutral lipids (NL), phospholipids (PL), and glycolipids (GL). The table shows only fatty acids that have abundances greater than 0.1%. The relative proportion of saturated (SAFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids is also given.
Table 6.
Cellular fatty acid composition of Chloromonas hindakii sp. nov. vegetative strain WP129 (= CCCryo 531-19) cultivated at 1 °C (n = 3) compared to field-collected cysts (from sample Rozcestí) in % of total lipids (TL) and in % of the three major lipid groups: Neutral lipids (NL), phospholipids (PL), and glycolipids (GL). The table shows only fatty acids that have abundances greater than 0.1%. The relative proportion of saturated (SAFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids is also given.
Fatty Acid | WP129 (= CCCryo 531-19) | Rozcestí |
---|
TL | NL | PL | GL | TL |
---|
14:0 | 0.7 ± 0.5 | 0.8 ± 0.6 | 1.1 ± 0.3 | 0 | 0.5 |
16:0 | 14.7 ± 6.1 | 15.6 ± 8.3 | 15.7 ± 1.4 | 10.4 ± 0.9 | 19.2 |
16:1 (9Z) | 0.3 ± 0.1 | 0 | 2.5 ± 1.3 | 0 | 1.9 |
16:1 (7Z) | 0.4 ± 0.3 | 0.5 ± 0.5 | 0 | 0 | 2.1 |
3t-16:1 | 0 | 0 | 4.6 ± 0.1 | 0 | 0 |
16:2 (7Z,10Z) | 0 | 0 | 0 | 0 | 3.2 |
16:3 (4Z,7Z,10Z) | 0 | 0 | 0 | 0 | 0.3 |
16:3 (7Z,10Z,13Z) | 2.1 ± 1.1 | 1.9 ± 1.4 | 1.5 ± 0.2 | 3.6 ± 0.3 | 2.7 |
16:4 (4Z,7Z,11Z,13Z) | 28.5 ± 4.6 | 30.6 ± 6.1 | 12.1 ± 0.6 | 29.5 ± 1.6 | 10.3 |
18:0 | 7.3 ± 6.8 | 6.7 ± 8.9 | 1.5 ± 0.6 | 14.5 ± 3.6 | 1.3 |
18:1 (11Z) | 0.5 ± 0.3 | 0.5 ± 0.4 | 1.1 ± 0.3 | 0 | 7.5 |
18:1 (9Z) | 9.8 ± 3.6 | 12.1 ± 5.2 | 8.4 ± 1.1 | 0 | 9.4 |
18:2 (9Z,12Z) | 3.4 ± 0.8 | 3.9 ± 1.0 | 3.4 ± 0.1 | 1.2 ± 0.7 | 4.8 |
18:3 (9Z,12Z,15Z) | 25.9 ± 3.7 | 21.4 ± 3.7 | 44.7 ± 1.7 | 33.2 ± 8.4 | 31.6 |
18:3 (6Z,9Z,12Z) | 0 | 0 | 0 | 0 | 0.5 |
18:4 (6Z,9Z,12Z,15Z) | 5.9 ± 0.2 | 6.0 ± 1.6 | 3.3 ± 1.1 | 7.4 ± 4.7 | 4.7 |
SAFA | 22.7 ± 10.9 | 23.1 ± 13.5 | 18.4 ± 1.0 | 25.0 ± 3.6 | 21 |
MUFA | 11.5 ± 3.6 | 13.1 ± 5.0 | 16.6 ± 0.8 | 0 | 20.9 |
PUFA | 65.8 ± 9.9 | 63.8 ± 8.5 | 65.1 ± 1.5 | 75.0 ± 3.6 | 58.1 |