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a–o . Hemichloris antarctica . a–c Cells with 2 chloroplasts in different views, d chloroplast in face view, covering the lower chloroplast, e, f internal structure of chloroplasts (in f relative large), g after division of chloroplasts, h start of cytoplasmatic division furrow from periphery marked by arrow (only 2 of the 4 chloroplasts represented), i–o stages of production of autospores: i, j with 2 chloroplasts, k, l already with 4 chloroplasts, m–o tetrads of different age. Drawings of living material grown in culture. Scale bar 10 l m
Source publication
The chlorococcalean genus Hemichloris is characterized by the possession of two chloroplasts per vegetative cell. The occurrence of a second species of the genus
is reported (H. polyspora sp. nov.). Just as H. antarctica it grows cryptoendolithically in sandstone in Southern Victoria Land, Antarctica. In H. antarctica propagation by two autospores...
Contexts in source publication
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... by light microscopy. With respect to Hemichloris antarctica a correction concern- ing morphology and life history is necessary. Young and fully developed cells do not possess one chloroplast, as was thought formerly (Tschermak-Woess and Friedmann 1984); they regularly possess two of them. This can best be stated, when they are observed in profile (Fig. 1a-c, e, i, j, n, o). They roughly have the form of flat saucers and may develop some lobes or lobes all over their surface ( Fig. 1b-d). Lobes of one chloroplast may reach into a recess of the other which often makes discrim- ination difficult (Fig. 1c). When seen in face view one chloroplast in part or totally may hide the other one (Fig. ...
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... and fully developed cells do not possess one chloroplast, as was thought formerly (Tschermak-Woess and Friedmann 1984); they regularly possess two of them. This can best be stated, when they are observed in profile (Fig. 1a-c, e, i, j, n, o). They roughly have the form of flat saucers and may develop some lobes or lobes all over their surface ( Fig. 1b-d). Lobes of one chloroplast may reach into a recess of the other which often makes discrim- ination difficult (Fig. 1c). When seen in face view one chloroplast in part or totally may hide the other one (Fig. 1c, ...
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... they regularly possess two of them. This can best be stated, when they are observed in profile (Fig. 1a-c, e, i, j, n, o). They roughly have the form of flat saucers and may develop some lobes or lobes all over their surface ( Fig. 1b-d). Lobes of one chloroplast may reach into a recess of the other which often makes discrim- ination difficult (Fig. 1c). When seen in face view one chloroplast in part or totally may hide the other one (Fig. 1c, ...
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... (Fig. 1a-c, e, i, j, n, o). They roughly have the form of flat saucers and may develop some lobes or lobes all over their surface ( Fig. 1b-d). Lobes of one chloroplast may reach into a recess of the other which often makes discrim- ination difficult (Fig. 1c). When seen in face view one chloroplast in part or totally may hide the other one (Fig. 1c, ...
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... in general comes about by production of two autospores (Fig. 1i-k); be- sides also four per mother cell occur in low rate ( Fig. 1m-o) and also eight very seldom come about, 16 are a rare exception. As a first step in propagation the chloroplasts divide. This comes about in isolated cells (Fig. 1g), but also in autospores still surrounded by the mother cell wall. Nuclear division starts later and the ...
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... in general comes about by production of two autospores (Fig. 1i-k); be- sides also four per mother cell occur in low rate ( Fig. 1m-o) and also eight very seldom come about, 16 are a rare exception. As a first step in propagation the chloroplasts divide. This comes about in isolated cells (Fig. 1g), but also in autospores still surrounded by the mother cell wall. Nuclear division starts later and the cytoplasmatic division furrow starts to grow inwards from the ...
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... in general comes about by production of two autospores (Fig. 1i-k); be- sides also four per mother cell occur in low rate ( Fig. 1m-o) and also eight very seldom come about, 16 are a rare exception. As a first step in propagation the chloroplasts divide. This comes about in isolated cells (Fig. 1g), but also in autospores still surrounded by the mother cell wall. Nuclear division starts later and the cytoplasmatic division furrow starts to grow inwards from the periphery (Fig. 1h). The 4-chloroplast stage may last for a relative long time. The relation of the number of autospores per mother cell in a 14 days culture on 3NBBM, ...
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... 1m-o) and also eight very seldom come about, 16 are a rare exception. As a first step in propagation the chloroplasts divide. This comes about in isolated cells (Fig. 1g), but also in autospores still surrounded by the mother cell wall. Nuclear division starts later and the cytoplasmatic division furrow starts to grow inwards from the periphery (Fig. 1h). The 4-chloroplast stage may last for a relative long time. The relation of the number of autospores per mother cell in a 14 days culture on 3NBBM, e.g. was: 60 dyads, 10 genuine tetrads, 1 Borodinella-stage (4 daughter cells, clearly resulting from a first dyad, the members of which had produced dyads once more, while still surrounded ...
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... the course of the former investigation in some cells the chloroplasts showed an accu- mulation of tiny structural elements (Tscher- mak-Woess and Friedmann 1984, Fig. 1i-k); their form was longitudinal, delimitation mostly not sharp. Even in some living cells from the natural habitat they were discerned. The chloroplasts appeared quite homogenous. In old cultures (age 3 to 5 or even 7 months), however, all of the cells or parts of them show the internal structure of the chloroplasts. Keeping the cultures ...
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... same also holds true for the cultures as a whole and in general. The nature and derivation of the internal structure in chloroplasts is treated in the chapter on TEM investigations (see below). Here it may suffice to state that its elements besides being centrally located, as depicted formerly, often are more widely and irregularly distributed (Fig. 1e, ...
Citations
... The community is named after its dominant member, the green alga Hemichloris antarctica (Tschermak-Woess and . Included in the community is a diverse assemblage of cyanobacteria and eukaryotic algae, including a second species of Hemichloris (Tschermak-Woess et al., 2006), the endemic species Heterococcus endolithicus (Darling et al., 1987), and members of the green algal genus Stichococcus and the cyanobacterial genera Gloeocapsa and Chroococcidiopsis. Members of Stichococcus, Gloeocapsa, and Chroococcidiopsis are all common constituents of terrestrial systems; Stichococcus bacillaris is generally considered to be a cosmopolitan inhabitant of subaerial environments, including lithic environments in Antarctica Broady, 1996;Hughes, 2006). ...
... The other genera were previously reported in Antarctica (see Table S6, Supporting Information, for detailed information). In contrast to these cosmopolitan genera, Hemichloris has never been found outside Antarctica (Tschermak-Woess et al. 2006). In our samples, this genus occurred in a cavity of a big boulder filled with gravel and water. ...
... In our samples, this genus occurred in a cavity of a big boulder filled with gravel and water. The two species belonging to this genus were previously reported from cryptoendolithic and endolithic samples from Victoria Land (Tschermak-Woess et al. 2006). Three sequences assigned to uncultured eukaryotes were also related to taxa found in Antarctica; one in a moss pillar in Hotoke lake (Syowa Oasis; Nakai et al. 2012), one in a microbial mat in Orange Pond (McMurdo Ice Shelf, Victoria Land; Jungblut et al. 2012) and the third one in soils near the Brazilian Antarctic station (NCBI match, unpublished). ...
The bacterial and microeukaryotic biodiversity was studied using pyrosequencing analysis on a 454 GS FLX+ platform of partial SSU rRNA genes in terrestrial and aquatic habitats of the Sør Rondane Mountains, including soils, on mosses, endolithic communities, cryoconite holes, and supraglacial and subglacial meltwater lenses. This inventory was complemented with Denaturing Gradient Gel Electrophoresis targeting Chlorophyta and Cyanobacteria. OTUs belonging to the Rotifera, Chlorophyta, Tardigrada, Ciliophora, Cercozoa, Fungi, Bryophyta, Bacillariophyta, Collembola and Nematoda were present with a relative abundance of at least 0.1% in the eukaryotic communities. Cyanobacteria, Proteobacteria, Bacteroidetes, Acidobacteria, FBP, and Actinobacteria were the most abundant bacterial phyla. Multivariate analyses of the pyrosequencing data revealed a general lack of differentiation of both eukaryotes and prokaryotes according to habitat type. However, the bacterial community structure in the aquatic habitats was dominated by the filamentous cyanobacteria Leptolyngbya and appeared to be significantly different compared with those in dry soils, on mosses, and in endolithic habitats. A striking feature in all datasets was the detection of a relatively large amount of sequences new to science, which underscores the need for additional biodiversity assessments in Antarctic inland locations.
... Elliptochloris occurs aquatically or terrestrially, living freely or symbiotically with fungi and in marine cnidarians (Aoki et al., 1998;Letsch et al., 2009;Tschermak-Woess, 1980). The two named species of Hemichloris are found cryptoendolithically in Antarctic rock (Tschermak-Woess and Friedmann, 1984;Tschermak-Woess et al., 2006), whereas Coccomyxa is a common lichen symbiont (Zoller and Lutzoni, 2003). Some of the taxa are difficult to culture, or are not yet in culture. ...
The 22 published chloroplast genomes of green algae, representing sparse taxonomic sampling of diverse lineages that span over one billion years of evolution, each possess a unique gene arrangement. In contrast, many of the >190 published embryophyte (land plant) chloroplast genomes have relatively conserved architectures. To determine the phylogenetic depth at which chloroplast gene rearrangements occur in green algae, a 1.5-4 kb segment of the chloroplast genome was compared across nine species in three closely related genera of Trebouxiophyceae (Chlorophyta). In total, four distinct gene arrangements were obtained for the three genera Elliptochloris, Hemichloris, and Coccomyxa. In Elliptochloris, three distinct chloroplast gene arrangements were detected, one of which is shared with members of its sister genus Hemichloris. Both species of Coccomyxa examined share the fourth arrangement of this genome region, one characterized by very long spacers. Next, the order of genes found in this segment of the chloroplast genome was compared across green algae and land plants. As taxonomic ranks are not equivalent among different groups of organisms, the maximum molecular divergence among taxa sharing a common gene arrangement in this genome segment was compared. Well-supported clades possessing a single gene order had similar phylogenetic depth in green algae and embryophytes. When the dominant gene order of this chloroplast segment in embryophytes was assumed to be ancestral for land plants, the maximum molecular divergence was found to be over two times greater in embryophytes than in trebouxiophyte green algae. This study greatly expands information about chloroplast genome variation in green algae, is the first to demonstrate such variation among congeneric green algae, and further illustrates the fluidity of green algal chloroplast genome architecture in comparison to that of many embryophytes.
The McMurdo Dry Valleys form the largest relatively ice-free area on the Antarctic continent. The perennially ice-covered lakes, ephemeral streams and extensive areas of exposed soil are subject to low temperatures, limited precipitation and salt accumulation. The dry valleys thus represent a region where life approaches its environmental limits. This unique ecosystem has been studied for several decades as an analog to environments on other planets, particularly Mars. For the first time, the detailed terrestrial research of the dry valleys is brought together here, presented from an astrobiological perspective. Chapters include a discussion on the history of research in the valleys, a geological background of the valleys, setting them up as analogs for Mars, followed by chapters on the various sub-environments in the valleys such as lakes, glaciers and soils. Includes concluding chapters on biodiversity and other analog environments on Earth.
The McMurdo Dry Valleys form the largest relatively ice-free area on the Antarctic continent. The perennially ice-covered lakes, ephemeral streams and extensive areas of exposed soil are subject to low temperatures, limited precipitation and salt accumulation. The dry valleys thus represent a region where life approaches its environmental limits. This unique ecosystem has been studied for several decades as an analog to environments on other planets, particularly Mars. For the first time, the detailed terrestrial research of the dry valleys is brought together here, presented from an astrobiological perspective. Chapters include a discussion on the history of research in the valleys, a geological background of the valleys, setting them up as analogs for Mars, followed by chapters on the various sub-environments in the valleys such as lakes, glaciers and soils. Includes concluding chapters on biodiversity and other analog environments on Earth.
The precise identification of the cyanobacteria that comprise an endolithic biofilm is hindered by difficulties in culturing the organisms found in these biofilms and a lack of previous molecular and ultrastructural data. This study characterizes, both at the ultrastructural and molecular level, two different cyanobacterial biofilms found in fissures of granite from continental Antarctica. Electron microscopy revealed structural differences between the two biofilms. One was only loosely adhered to the substrate, while the other biofilm showed a closer association between cells and rock minerals and was tightly attached to the substrate. Cells from both biofilms where ultrastructurally distinct, displaying, for instance, clear differences in their sheaths. The amounts of EPS and their organization associated with the cyanobacteria may determine the differences in adhesion and effects on the lithic substrate observed in the biofilms. By sequencing part of the 16S rRNA gene, the two cyanobacteria were also genetically characterized. The gene sequence of the cells comprising the biofilm that was tightly attached to the lithic substrate showed most homology with that of an endolithic cyanobacterium from Switzerland (AY153458), and the cyanobacterial type loosely adhered to the rock, clustered with Acaryochloris marina, the only organism unequivocally known to contain chlorophyll d. This study reveals the presence of at least two different types of endolithic biofilm, dominated each by a single type of cyanobacterium, able to withstand the harsh conditions of the Antarctic climate.
Neustupa J., Eliáš M., Škaloud P., Němcová Y. and Šejnohová L. 2011. Xylochloris irregularis gen. et sp. nov. (Trebouxiophyceae, Chlorophyta), a novel subaerial coccoid green alga. Phycologia 50: 57–66. DOI: 10.2216/08-64.1
The phylogenetic diversity of subaerial coccoid green algae remains still poorly explored. We characterised in detail two unicellular green algae found on tropical trees in Singapore. Light microscopy revealed morphological identity of these two strains. Depending on the age of cultures, the cells were spherical to cylindrical, and ranged in size from 13.5 to 20.5 µm. Each cell contained a pyrenoid-bearing parietal chloroplast that was typically somewhat detached from the plasma membrane on its parietal side. The cells reproduced by 4–16 globular autospores. The 18S rRNA gene sequences of the two strains differed by only a single nucleotide, indicating probable conspecificity. Because the strains were morphologically most comparable to species of the genus Parietochloris, we determined the 18S rRNA gene sequences from authentic strains of three Parietochloris species (P. alveolaris, P. cohaerens and P. ovoidea) for comparison. Molecular phylogenetic analyses placed all five examined strains into the class Trebouxiophyceae. The two novel tropical strains were found to be an independent lineage without an obvious sister group. The type species of the genus Parietochloris, P. alveolaris formed a monophyletic lineage with Parietochloris pseudalveolaris. Finally, P. cohaerens and P. ovoidea fell into another independent clade that also contained Lobosphaera tirolensis, L. incisa and Myrmecia bisecta, indicating that the genus Parietochloris as previously defined is polyphyletic. Based on our morphological and molecular phylogenetic data, we describe the two novel tropical strains as representatives of a new trebouxiophycean genus and species, Xylochloris irregularis gen. et sp. nov.
