Klebsormidium Strains Research Articles

Ecophysiological Response Against Temperature in Klebsormidium (Streptophyta) Strains Isolated From Biological Soil Crusts of Arctic and Antarctica Indicate Survival During Global Warming

Global warming, as global problem, may particularly affect the vegetation of the Polar Regions. Biological soil crusts (BSCs) as pioneer communities perform a variety of important ecological functions under the harsh environmental conditions at high latitudes. The green algal genus Klebsormidium is a common member of BSCs and in the present study, the ecophysiological resilience to temperature stress of 20 strains from Arctic and Antarctica were investigated. All 20 Klebsormidium strains exhibited the capability to grow under a wide temperature range (from 6 to 28 °C) and hence were characterized as psychrotolerant with optimum growth temperatures between 18 °C and 26 °C. Statistical analyses showed no significant differences in optimum growth temperature. However, growth rates at optimal temperatures varied between strains and indicated infraspecific physiological plasticity. Furthermore, correlation with the sampling sites as well as different BSC types were examined but no significance was confirmed. Our results revealed that Polar Klebsormidium strains are able to survive such changing conditions, and even benefit from higher environmental temperatures.

Cold Acclimation Improves the Desiccation Stress Resilience of Polar Strains of Klebsormidium (Streptophyta).

Biological soil crusts (BSCs) are complex communities of autotrophic, heterotrophic, and saprotrophic (micro)organisms. In the polar regions, these biocrust communities have essential ecological functions such as primary production, nitrogen fixation, and ecosystem engineering while coping with extreme environmental conditions (temperature, desiccation, and irradiation). The microalga Klebsormidium is commonly found in BSCs all across the globe. The ecophysiological resilience of various Klebsormidium species to desiccation and other stresses has been studied intensively. Here we present the results of transcriptomic analyses of two different Klebsormidium species, K. dissectum and K. flaccidum, isolated from Antarctic and Arctic BSCs. We performed desiccation stress experiments at two different temperatures mimicking fluctuations associated with global change. Cultures grown on agar plates were desiccated on membrane filters at 10% relative air humidity until the photosynthetic activity as reflected in the effective quantum yield of photosystem II [Y(II)] ceased. For both species, the response to dehydration was much faster at the higher temperature. At the transcriptome level both species responded more strongly to the desiccation stress at the higher temperature suggesting that adaptation to cold conditions enhanced the resilience of both algae to desiccation stress. Interestingly, the two different species responded differently to the applied desiccation stress with respect to the number as well as function of genes showing differential gene expression. The portion of differentially expressed genes shared between both taxa was surprisingly low indicating that both Klebsormidium species adapted independently to the harsh conditions of Antarctica and the Arctic, respectively. Overall, our results indicate that environmental acclimation has a great impact on gene expression and the response to desiccation stress in Klebsormidium.

Review on the biotechnological and nanotechnological potential of the streptophyte genus Klebsormidium with pilot data on its phycoprospecting and polyphasic identification in Bulgaria

This review provides data on the possibilities for commercial use of algae of the green streptophyte genus Klebsormidium. It is one of the basal algal progenitors of land plants and shows many mechanisms and features which allow its adaptation to different environmental stresses associated with land colonization. This has led to formation of structures and compounds with countless possible applications in biotechnology and nanotechnology, starting from food to pharmaceuticals and biofuels. Therefore, the present work aims to provide: (1) a review on this yet neglected topic for the first time; (2) reliable identification using the polyphasic taxonomic approach of three local Klebsormidium strains isolated from soils of two protected areas in Bulgaria (Kresnendko Defile and National park Rila). It also outlines the cultivation advantages of Klebsormidium broad tolerance to harsh conditions and its reproductive features (easy disintegration and possibility to produce resting stages). The possibility to use inoculum of akinetes in soil algalization as biofertilizers is proposed. The results from standard microscopical identification and molecular data (ITS and rbcL, used separately and in combination), combined in the applied polyphasic approach led to distinguishing between geographically distinct strains collected at different altitudes. After identification of two strains (ACUS 00001 and ACUS 00014) as belonging to Klebsormidium dissectum and of ACUS 00207 as belonging to Klebsormidium klebsii, the similarity of the latter taxon with K. nitens is discussed.

Usual alga from unusual habitats: Biodiversity of Klebsormidium (Klebsormidiophyceae, Streptophyta) from the phylogenetic superclade G isolated from biological soil crusts

Seven new species and two varieties of Klebsormidium were described using an integrative approach on the base of 28 strains from the poorly studied phylogenetic superclade G. These strains originated from the unusual and exotic habitats (semi-deserts, semi-arid shrublands, Mediterranean shrub and deciduous vegetation, temperate Araucaria forests, peat bogs, dumps after coal mining, maritime sand dunes etc.) of four continents (Africa, South and North America, and Europe). Molecular phylogenies based on ITS-1,2, rbcL gene and concatenated dataset of ITS-1,2–rbcL, secondary structure of ITS-2, morphology, ecology and biogeography, micrographs and drawings of the investigated strains were assessed. Additionally, phylogeny and morphology of 18 Klebsormidium strains from other lineages isolated from the same localities (different vegetation types of Chile and maritime sand dunes of Germany) were investigated for the comparison with representatives of clade G. Clade G Klebsormidium is characterized by distant phylogenetic position from the other Klebsormidium lineages and prominent morphology: four-lobed chloroplasts and mostly short swollen cells in young culture, compact small pyrenoids, curved or disintegrated filaments, unusual elongation of cells in old culture, formation of specific cluster- and knot-like colonies on agar surface, especially prominent in strains isolated from desert regions, from which the group probably originated. Comparison of Klebsormidium diversity from different biogeographic regions showed that the representatives of clade G are common algae in regions of the southern hemisphere (South Africa and Chile) and rare representatives in terrestrial ecosystems of the northern hemisphere. Further investigation of mostly unstudied territories of the southern hemisphere could bring many surprises and discoveries, leading to a change of the present concept that Klebsormidium is cosmopolitan in distribution.

Biological Soil Crusts of Arctic Svalbard-Water Availability as Potential Controlling Factor for Microalgal Biodiversity.

In the present study the biodiversity of biological soil crusts (BSCs) formed by phototrophic organisms were investigated on Arctic Svalbard (Norway). These communities exert several important ecological functions and constitute a significant part of vegetation at high latitudes. Non-diatom eukaryotic microalgal species of BSCs from 20 sampling stations around Ny-Ålesund and Longyearbyen were identified by morphology using light microscopy, and the results revealed a high species richness with 102 species in total. 67 taxa belonged to Chlorophyta (31 Chlorophyceae and 36 Trebouxiophyceae), 13 species were Streptophyta (11 Klebsormidiophyceae and two Zygnematophyceae) and 22 species were Ochrophyta (two Eustigmatophyceae and 20 Xanthophyceae). Surprisingly, Klebsormidium strains belonging to clade G (Streptophyta), which were so far described from Southern Africa, could be determined at 5 sampling stations. Furthermore, comparative analyses of Arctic and Antarctic BSCs were undertaken to outline differences in species composition. In addition, a pedological analysis of BSC samples included C, N, S, TP (total phosphorus), and pH measurements to investigate the influence of soil properties on species composition. No significant correlation with these chemical soil parameters was confirmed but the results indicated that pH might affect the BSCs. In addition, a statistically significant influence of precipitation on species composition was determined. Consequently, water availability was identified as one key driver for BSC biodiversity in Arctic regions.

Ecophysiological traits of various genotypes of a green key alga in biological soil crusts from the semi-arid Colorado Plateau, USA

Biological soil crusts (BSCs) represent a micro-ecosystem consisting of various microorganisms including algae in drylands worldwide. The green algal genus Klebsormidium is a typical member of such communities, and because of its filamentous morphology and sticky cells, it plays an ecological key role in the stabilization of soil surfaces. In the present study, we investigated for the first time the phylogeny and ecophysiological performance of five BSC Klebsormidium strains from the semi-arid Colorado Plateau, USA. The molecular phylogeny of rbcL sequences showed that these strains belong to two subclades, which have been described before from mainly humid habitats. During controlled dehydration, the effective quantum yield of photosystem II decreased during 370–430 min of exposure. After controlled rehydration, all strains recovered between 32.9 and 97.6% of the control, but with significant differences depending on the genetic lineage. All five isolates grew between 18.1 and 27.9 °C, with isolate-specific optimal growth temperatures. Similarly, all strains were grown under increasing photon fluence rates from 4 to 110 μmol photons m−2 s−1 with optima under the higher tested light levels. Two strains showed inhibition at higher photon fluence rates and hence low light requirements for growth. Photosynthesis under increasing photon fluence rates up to 314 μmol photons m−2 s−1 indicated again low light requirements, but with no photoinhibition. All results underline a pronounced plasticity of the ecophysiological traits of the investigated Klebsormidium strains, which allow these terrestrial algae to exploit the environmental gradients within BSCs in arid regions.

Habitat-specific composition of morphotypes with low genetic diversity in the green algal genus Klebsormidium (Streptophyta) isolated from biological soil crusts in Central European grasslands and forests

ABSTRACT Terrestrial filamentous green algae of the widely distributed, cosmopolitan genus Klebsormidium (Klebsormidiophyceae, Streptophyta) are typical components of biological soil crusts (BSCs). These communities occur in all climatic zones and on all continents, where soil moisture is limited or where there has been disturbance. BSCs form water-stable aggregates that have important ecological roles in primary production, nitrogen fixation, nutrient cycling, water retention and stabilization of soils. Although available data on Klebsormidium are limited, its functional importance in BSCs is regarded as high. Therefore, in the present study Klebsormidium strains were isolated from BSCs sampled from various grassland and forest plots of different land use intensities in Central Europe, as provided by the Biodiversity Exploratories, and its intraspecific genetic diversity was evaluated. Previous phylogenetic analyses revealed a relationship between sequence similarity and habitat preference with a higher genetic diversity than expected from a morphological classification. We isolated and sequenced 75 Klebsormidium strains. The molecular phylogeny based on the ITS regions showed that all strains belong to either the previously described clade B/C or clade E. This classification was supported by morphological characteristics: strains assigned to clade B/C were identified as Klebsormidium cf. flaccidum or Klebsormidium cf. dissectum, and strains from clade E as K. nitens or Klebsormidium cf. subtile. Within one clade the strains showed low sequence divergences. These minor differences were independent of the sampling region and land use intensity. Interestingly, most of the strains assigned to clade E were isolated from forest sites, whereas strains from clade B/C occurred equally in grassland and forest sites. Therefore, it is reasonable to assume that habitat with its microenvironmental conditions, and not biogeography, controls genetic diversity in Klebsormidium.

Ecophysiological Response on Dehydration and Temperature in Terrestrial Klebsormidium (Streptophyta) Isolated from Biological Soil Crusts in Central European Grasslands and Forests.

The green algal genus Klebsormidium (Klebsormidiophyceae, Streptophyta) is a typical member of biological soil crusts (BSCs) worldwide. Ecophysiological studies focused so far on individual strains and thus gave only limited insight on the plasticity of this genus. In the present study, 21 Klebsormidium strains (K. dissectum, K. flaccidum, K. nitens, K. subtile) from temperate BSCs in Central European grassland and forest sites were investigated. Photosynthetic performance under desiccation and temperature stress was measured under identical controlled conditions. Photosynthesis decreased during desiccation within 335-505min. After controlled rehydration, most isolates recovered, but with large variances between single strains and species. However, all K. dissectum strains had high recovery rates (>69%). All 21 Klebsormidium isolates exhibited the capability to grow under a wide temperature range. Except one strain, all others grew at 8.5°C and four strains were even able to grow at 6.2°C. Twenty out of 21 Klebsormidium isolates revealed an optimum growth temperature >17°C, indicating psychrotrophic features. Growth rates at optimal temperatures varied between strains from 0.26 to 0.77μ day-1. Integrating phylogeny and ecophysiological traits, we found no phylogenetic signal in the traits investigated. However, multivariate statistical analysis indicated an influence of the recovery rate and growth rate. The results demonstrate a high infraspecific and interspecific physiological plasticity, and thus wide ecophysiological ability to cope with strong environmental gradients. This might be the reason why members of the genus Klebsormidium successfully colonize terrestrial habitats worldwide.

Influence of substrate and pH on the diversity of the aeroterrestrial alga Klebsormidium (Klebsormidiales, Streptophyta): a potentially important factor for sympatric speciation

:Our knowledge of the processes involved in speciation of microalgae remains highly limited. In the present study, we investigated a potential role of ecological speciation processes in diversification of the filamentous green alga Klebsormidium. We examined 12 strains representing four different genotypes. The strains were collected from sandstone and limestone rocks and were cultivated at five different pH levels ranging from pH 4 to pH 8. We determined the responses of the 12 strains to the experimental pH conditions by (1) measuring the effective quantum yield of photosystem II, and (2) determining the growth rates after cultivation at different pH levels. Strong differences were found between the results obtained by these two methods. Direct counting of cells revealed a strong ecological differentiation of strains of Klebsormidium isolated from different substrate types. Strains isolated from limestone showed the highest growth rates at higher pH levels; whereas, the strains isolated from sandstone exhibited two distinct growth responses with optima at pH 5 and 6, respectively. In contrast, the effective quantum yield of photosystem II was always down-regulated at lower pH values, probably due to dissolved inorganic carbon limitation. In general, we determined distinct ecophysiological differentiation among distantly and closely related lineages, thereby corroborating our hypothesis that the sympatric speciation of terrestrial algae is driven by ecological divergence. We clearly showed that pH is a critical ecological factor that influences the diversity of autotrophic protists in terrestrial habitats.

Living in biological soil crust communities of African deserts—Physiological traits of green algal Klebsormidium species (Streptophyta) to cope with desiccation, light and temperature gradients

Green algae of the genus Klebsormidium (Klebsormidiales, Streptophyta) are typical members of biological soil crusts (BSCs) worldwide. The phylogeny and ecophysiology of Klebsormidium has been intensively studied in recent years, and a new lineage called superclade G, which was isolated from BSCs in arid southern Africa and comprising undescribed species, was reported. Three different African strains, that have previously been isolated from hot-desert BSCs and molecular-taxonomically characterized, were comparatively investigated. In addition, Klebsormidium subtilissimum from a cold-desert habitat (Alaska, USA, superclade E) was included in the study as well. Photosynthetic performance was measured under different controlled abiotic conditions, including dehydration and rehydration, as well as under a light and temperature gradient.All Klebsormidium strains exhibited optimum photosynthetic oxygen production at low photon fluence rates, but with no indication of photoinhibition under high light conditions pointing to flexible acclimation mechanisms of the photosynthetic apparatus. Respiration under lower temperatures was generally much less effective than photosynthesis, while the opposite was true for higher temperatures. The Klebsormidium strains tested showed a decrease and inhibition of the effective quantum yield during desiccation, however with different kinetics. While the single celled and small filamentous strains exhibited relatively fast inhibition, the uniserate filament forming isolates desiccated slower. Except one, all other strains fully recovered effective quantum yield after rehydration. The presented data provide an explanation for the regular occurrence of Klebsormidium strains or species in hot and cold deserts, which are characterized by low water availability and other stressful conditions.

Biodiversity of Klebsormidium (streptophyta) from alpine biological soil crusts (alps, tyrol, Austria, and Italy).

Forty Klebsormidium strains isolated from soil crusts of mountain regions (Alps, 600–3,000 m elevation) were analyzed. The molecular phylogeny (internal transcribed spacer rDNA sequences) showed that these strains belong to clades B/C, D, E, and F. Seven main (K. flaccidum, K. elegans, K. crenulatum, K. dissectum, K. nitens, K. subtile, and K. fluitans) and four transitional morphotypes (K. cf. flaccidum, K. cf. nitens, K. cf. subtile, and K. cf. fluitans) were identified. Most strains belong to clade E, which includes isolates that prefer humid conditions. One representative of the xerophytic lineage (clade F) as well as few isolates characteristic of temperate conditions (clades B/C, D) were found. Most strains of clade E were isolated from low/middle elevations (<1,800 m above sea level; a.s.l.) in the pine‐forest zone. Strains of clades B/C, D, and F occurred sporadically at higher elevations (1,548–2,843 m a.s.l.), mostly under xerophytic conditions of alpine meadows. Comparison of the alpine Klebsormidium assemblage with data from other biogeographic regions indicated similarity with soil crusts/biofilms from terrestrial habitats in mixed forest in Western Europe, North America, and Asia, as well as walls of buildings in Western European cities. The alpine assemblage differed substantially from crusts from granite outcrops and sand dunes in Eastern Europe (Ukraine), and fundamentally from soil crusts in South African drylands. Epitypification of the known species K. flaccidum, K. crenulatum, K. subtile, K. nitens, K. dissectum, K. fluitans, K. mucosum, and K. elegans is proposed to establish taxonomic names and type material as an aid for practical studies on these algae, as well as for unambiguous identification of alpine strains. New combination Klebsormidium subtile (Kützing) Mikhailyuk, Glaser, Holzinger et Karsten comb. nov. is made.

Molecular evidence for the polyphyletic origin of low pH adaptation in the genus Klebsormidium (Klebsormidiophyceae, Streptophyta)

Background and aims – Algae living in low pH environments have been the subject of numerous studies, but their phylogenetic relationships with relatives found in non-acidic habitats are poorly known. In the present study we analyzed the morphology and phylogeny of acid-adapted strains of Klebsormidium, a genus of filamentous green algae frequently present in low pH environments. Methods – Eighteen strains of Klebsormidium were collected from from low pH habitats in Europe and U.S.A., mainly from terrestrial sites affected directly or indirectly by carbon mining activities. These algae were isolated in culture and their phylogenetic relationships were studied using rbcL and ITS rDNA sequence data in a concatenated dataset. Key results – In the molecular phylogeny the strains of Klebsormidium living in low pH habitats formed a polyphyletic assemblage. They were representative of sixteen lineages and corresponded morphologically to six species (K. crenulatum, K. elegans, K. flaccidum, K. fluitans, K. nitens, K. scopulinum), with the exception of four strains for which an unambiguous identification was not possible. Conclusions – The genus Klebsormidium is a group of morphologically and physiologically dynamic algae in which the capacity of adaptation to low pH conditions has been developed multiple times independently. Extreme acidophilic populations probably originate from populations of various species growing locally when strongly acidic habitats become available. For the acid-adapted lineages of Klebsormidium examined here the current known distribution is geographically restricted, with the exception of a lineage containing strains from Czech Republic, New Zealand and Ohio.

Plasmolysis effects and osmotic potential of two phylogenetically distinct alpine strains of Klebsormidium (Streptophyta)

The osmotic potential and effects of plasmolysis were investigated in two different Klebsormidium strains from alpine habitats by incubation in 300-2,000 (3,000) mM sorbitol. Several members of this genus were previously found to tolerate desiccation in the vegetative state yet information was lacking on the osmotic potentials of these algae. The strains were morphologically determined as Klebsormidium crenulatum and Klebsormidium nitens. These species belong to distinct clades, as verified by phylogenetic analysis of the rbcL gene. K. crenulatum is part of to the K. crenulatum/mucosum ('F' clade) and K. nitens of the 'E2' clade. Plasmolysis occurred in K. crenulatum at 800mM sorbitol (961mOsmolkg(-1), Ψ = -2.09MPa) and in K. nitens at 600mM sorbitol (720mOsmolkg(-1), Ψ = -1.67MPa). These are extraordinarily high osmotic values (very negative osmotic potentials) compared with values reported for other green algae. In K. crenulatum, the maximum photosynthetic rate (Pmax) in the light-saturated range was 116μmol O(2) h(-1)mg(-1) chl a. Incubation in 1,000mM sorbitol decreased Pmax to 74.1% of the initial value, whereas 2,000mM sorbitol (Ψ = -5.87MPa) lead to an almost complete loss of oxygen production. In K. nitens, Pmax was 91μmol O(2) h(-1)mg(-1) chl a under control conditions and incubation in 800mM sorbitol did not decrease Pmax, 2,000mM sorbitol decreased Pmax only to about 62.6% of the initial value whereas 3,000mM sorbitol stopped oxygen evolution. This indicated a broader amplitude for photosynthesis in the examined strain of K. nitens. Control samples and samples plasmolysed for 3h in 800mM sorbitol (K. nitens), 1,000mM sorbitol (K. crenulatum), or 2,000mM sorbitol were investigated by transmission electron microscopy after chemical or high-pressure freeze fixation. In cells undergoing plasmolysis the protoplasts were retracted from the cell wall, the cytoplasm appeared dense, vacuoles were small and fragmented, and the cytoplasm was filled with ribosomes. Thin cytoplasmic strands were connected to the cell wall; 2,000mM sorbitol increased the effect. The content of soluble carbohydrates in these two strains was investigated by HPLC, as this is one known mechanism for cells to maintain high osmotic pressure of the cytosol. Both Klebsormidium species contained diverse soluble carbohydrates, including a dominant mixed peak of unidentified oligosaccharides, and more minor amounts of raffinose, sucrose, glucose, xylose, galactose, mannose, inositol, fructose, glycerol, mannitol, and sorbitol. The total content of soluble carbohydrates was approximately 1.2% of the dry weight, indicating that this is not a major factor contributing to the high osmotic potential in these strains of Klebsormidium.

Freezing and desiccation injury resistance in the filamentous green alga Klebsormidium from the Antarctic, Arctic and Slovakia

The freezing and desiccation tolerance of 12 Klebsormidium strains, isolated from various habitats (aero- terrestrial, terrestrial, and hydro-terrestrial) from distinct geographical regions (Antarctic - South Shetlands, King George Island, Arctic - Ellesmere Island, Svalbard, Central Europe - Slovakia) were studied. Each strain was exposed to several freezing (�4 ◦ C, �40 ◦ C, �196 ◦ C) and desiccation (+4 ◦ Ca nd +20 ◦ C) regimes, simulating both natural and semi-natural freeze-thaw and desiccation cycles. The level of resistance (or the survival capacity) was evaluated by chlorophyll a content, viability, and chlorophyll fluorescence evaluations. No statistical differences (Kruskal-Wallis tests) between strains originat- ing from different regions were observed. All strains tested were highly resistant to both freezing and desiccation injuries. Freezing down to �196 ◦ C was the most harmful regime for all studied strains. Freezing at �4 ◦ C did not influence the sur- vival of studied strains. Further, freezing down to �40 ◦ C (at a speed of 4 ◦ C/min) was not fatal for most of the strains. RDA analysis showed that certain Antarctic and Arctic strains did not survive desiccation at +4 ◦ C; however, freezing at �40 ◦ C, as well as desiccation at +20 ◦ C was not fatal to them. On the other hand, other strains from the Antarctic, the Arctic, and Central Europe (Slovakia) survived desiccation at temperatures of +4 ◦ C, and freezing down to �40 ◦ C. It appears that

Variation and taxonomic significance of some morphological features in European strains of Klebsormidium (Klebsormidiophyceae, Streptophyta)

Variation and taxonomic significance of some morphological features in European strains of Klebsormidium (Klebsormidiophyceae, Streptophyta)

Phylogeny of Klebsormidium (Kelbsormidiales; Charophyta) Based on rbcL, atpB, coxIII and nad5 Sequence Data

AbstractThe charophycean order Klebsormidiales consists of two unbranched filamentous lineages, the fresh water Entransia and the semiterrestrial Klebsormidium. Molecular data have supported the close relationship Klebsormidiales have with land plants. A monograph exists for the European species of Klebsormidium; this monograph provides a cladistic analysis of morphological characteristics for eight Klebsormidium species, but a species level molecular phylogenetic analysis has not yet been performed for the group. We have obtained 50 strains of Klebsormidium, representing 11 morphological species, both from nature and from culture collections. Phylogenetic analyses using rbcL, atpB, coxIII and nad5 gene sequence data from these strains and 40 outgroup sequences suggest that several traditional Klebsormidium species may not be monophyletic.

The occurrence of urease/urea amidolyase and glycollate oxidase/dehydrogenase inKlebsormidiumspp. and members of the ulotrichales

Six strains of Klebsormidium flaccidum, one each of Klebsormidium subtilissimum, Ulothrix fimbriata, Stichococcus mirabilis, Stichococcus bacillaris, Pseudostichococcus monallantoides and Schizomeris leibleinii have been examined for the presence of urease or urea amidolyase (UAL-ase) and glycollate oxidase or glycollate dehydrogenase. All the Klebsormidium strains contained urease and glycollate oxidase; all the other algae examined contained UAL-ase and glycollate dehydrogenase. There was no evidence for the presence of both urease and UAL-ase activities in the same species. These results are consistent with the separation of the genus Klebsormidium from the Ulotrichales and its inclusion in the Charophyceae as defined by Stewart & Mattox (1975).