Calochaete cimrmanii Hauer, Bohunická & Mühlsteinová, 2013

Hauer, Tomáš, Bohunická, Markéta & Mühlsteinová, Radka, 2013, Calochaete gen. nov. (Cyanobacteria, Nostocales), a new cyanobacterial type from the “ páramo ” zone in Costa Rica, Phytotaxa 109 (1), pp. 36-44 : 38-40

Calochaete cimrmanii Hauer, Bohunická & Mühlsteinová , sp. nov. ( Figs 1A–P )

The description corresponds to that of the genus.

Type:— COSTA RICA. Chirripó Mountain slope, 9° 29’ 58” N, 83° 30’ 24” W, surface soil in páramo, dried specimen from culture of sample, colle. M. Bohunická and J. Mareš, 6 March 2010 (holotype: CBFS! A–015). Type strain: CCALA 1012 .

Habitat: —Surface soil in “páramo” (tropical high montane vegetation).

Etymology:—The species is named after the mythical Czech scientist, dramatist, poet, and writer Jára Cimrman.

Observations:—The life cycle contains several morphologically distinct stages ( Fig. 1 ). One was described above, i.e long, gradually tapering, heteropolar filaments ( Figs 1A, B, P ). The second consists of hormogonia composed of short, isodiametric, barrel-shaped to spherical cells resembling in morphology Nostoc Vaucher ex Bornet et Flahault (1888: 181) types lacking the sheath ( Fig. 1E ). Some cells within the hormogonia grow in size and change their shape to spherical ( Figs 1D, O ). Cells may sometimes divide in more than one plane ( Figs 1L, M, O ), but never form a true branch. A new filament then germinates from the hormogonia ( Fig. 1C ). The first cell of the filament becomes a heterocyte. The hormogonia with large spherical cells (e.g. Fig. 1D ) occur in young cultures only.

Our strain differs from the morphologically similar genus Calothrix Agardh ex Bornet et Flahault (1886: 345) by the absence of a terminal hair and frequent false single or double branching ( Figs 1G, H, N ). As notable from Fig. 2 , the 16S rRNA sequence of Calochaete cimrmanii is very distant from members of Rivulariaceae and is more related to Microchaetaceae . The most similar are sequences of Tolypothix strains UAM 332, 334, 337 and PCC 7504, but the degree of tapering is significantly lower in these strains. The low degree of tapering itself is one of the key diacritical features of the genus Tolypothrix Kützing ex Bornet et Flahault (1887: 118) , which is accepted in both the botanical ( Komárek & Anagnostidis 1989) and bacteriological ( Castenholz 2001) literatures. From the above mentioned Tolypothrix strains, Calochaete cimrmanii differs also by living in a significantly different –non-aquatic, high mountain– habitat.

Comparison of the secondary structures of 16S-23S ITS is of taxonomic importance according to Johansen et al. (2011). To illustrate specificity and the rate of relatedness of the different morphologically similar taxa included in our study, we provide the two most conserved ITS domains, the D1-D1’ and Box-B helices for Calochaete cimrmanii , Tolypothrix sp. PCC 7504 from cluster “B”, Spirirestis rafaelensis Flechtner et Johansen in Flechtner et al. (2002: 6) WJT-71-NPBG6 from cluster “A”, and Calothrix sp. PCC 7507 from a cluster phylogenetically distant from Calochaete ( Fig. 3 ). It can be clearly seen that Calochaete cimrmanii and Tolypothrix PCC 7504 are significantly similar in both structures, especially in the basal parts and the bottom halves of the loops ( Figs 3A, B, E, F ). Concurrently, there are obvious differences in the top portions of the loops, supporting our decision to separate Calochaete from the traditional genus Tolypothix. The similarity of the secondary structures decreases when comparing Calochaete with Spirirestis as a representative of cluster “A” and the most phylogenetically but supposedly morphologically related Calothrix .

Figures

FIGURE 1. Morphological variability of the strain CCALA 1012. A. Mature heteropolar filaments. B. detail of well-developed filament with terminal heterocyte. C. A filament germinating from hormogonium with enlarged cells. D, E. Formation of a hormogonium in a filament and hormogonia with enlarging cells. F. Middle part of a mature filament with thin colorless sheath. G. Double branching. H. Single branching. I. Young filament with distinct tapering. J. Swollen bases of mature filaments. K. Shape of the terminal cells. L, M. Enlarged cells in hormogonia dividing in two planes (marked with arrowheads). N. Young growing thallus with single branching. O. Hormogonia and their development after release from mother sheath. M. Well-developed filaments. Bar length = 20 µm.

FIGURE 2. Phylogenetic analysis based on 16S rDNA sequence with 70 OTUs, using neigbor-joining topology. The support values are given for Neighbor-joining, Maximum likelihood, and Bayesian posterior probabilities. The cut-off values for bootstrap and probability are 50 (0.5 resp). Our reference strain CCALA 1012 (accession number HF912386) is printed in bold. Clusters A and B represent clades with members of the Microchaetaceae family demonstrating heterogeneity of the genus Tolypothrix and the whole family Microchaetaceae.

FIGURE 3. Secondary structures of the D1- D1’(row one) and Box-B helices (row two) of strain CCALA 1012 and related strains of types similar either morphologically (Calothrix) or molecularly (members of Microchaetaceae—Tolypothrix and Spirirestis). A, E. Calochaete cimrmanii CCALA 1012. B, F. Tolypothrix sp. PCC 7504. C, G. Spirirestis rafaelensis WJT-71-NPBG6. D, H. Calothrix sp. PCC 7507.