Kalinella bambusicola gen. et sp. nov. (Trebouxiophyceae, Chlorophyta), a novel coccoid Chlorella-like subaerial alga from Southeast Asiap re_534 159..169 SUMMARYThe traditional green algal genus Chlorella, which comprised coccoid algae surrounded by a smooth cell wall and reproducing solely by autosporulation, has proved to be polyphyletic and extremely diverse in phylogenetic terms. We studied a new subaerial Chlorella-like strain CAUP H7901 and morphological, ultrastructural, and molecular phylogenetic investigations indicated that it represents a new lineage of the trebouxiophycean Watanabea clade, dissimilar from other members of this group. The alga has globular coccoid cells with a single parietal pyrenoid-bearing chloroplast. The pyrenoid is transected by multiple radial thylakoid bands. The alga reproduces exclusively by means of asexual autospores of unequal size. In 18S rDNA sequence phylogenies, it was nested within the Watanabea clade close to lineages containing Chlorella saccharophila, Chlorella luteoviridis, Heveochlorella hainangensis, and two uncharacterized strains, but alternative positions within the Watanabea clade could not be rejected by an approximately unbiased (AU) test. Here we describe this organism as a new genus and species Kalinella bambusicola gen. et sp. nov. Furthermore, we describe Heterochlorella gen. nov. to accommodate a species previously referred to as Chlorella luteoviridis.

The diversity of green microalgae in subaerial habitats remains largely unexplored and a number of new genus- and species-level lineages have been discovered recently. The traditional green algal genus, Chlorella, which accommodated coccoid unicellular green algal species with globular to oval cells, reproducing entirely by autospores, has been found to be polyphyletic. In this study, we provide a detailed characterization of two strains of microalgae isolated from tree bark in the Mediterranean. These algae share the general Chlorella-like morphology and their 18S rRNA and rbcL gene sequences place them in the Trebouxiophyceae. Strain CAUP H8401 forms an independent trebouxiophycean lineage, together with three previously published 18S rRNA gene environmental sequences of undescribed microalgae, which were retrieved from profoundly different habitats. In contrast, strain CAUP H7902 is related to Kalinella bambusicola in the Watanabea clade of the Trebouxiophyceae on the basis of its 18S rRNA gene sequence. This relationship is also supported by the rbcL gene sequence, acquired from the type strain of K. bambusicola. The investigated strains are described as representatives of a novel species in a new genus, Leptochlorella corticola gen. et sp. nov., and a novel species, Kalinella apyrenoidosa sp. nov., according to the International Code of Nomenclature for Algae, Fungi and Plants.

Filamentous conjugating green microalgae (Zygnematophyceae, Streptophyta) belong to the most common primary producers in polar hydro-terrestrial environments such as meltwater streamlets and shallow pools. The mats formed by these organisms are mostly composed of sterile filaments with Zygnema morphology, but the extent of their diversity remains unknown. Traditional taxonomy of this group is based on reproductive morphology, but sexual reproduction (conjugation and formation of resistant zygospores) is very rare in extreme conditions. In the present study we gave the first record of zygospore formation in Svalbard field samples, and identified conjugating filaments as Zygnemopsis lamellata and Zygnema cf. calosporum. We applied molecular phylogeny to study genetic diversity of sterile Zygnema filaments from Svalbard in the High Arctic. Based on analysis of 143 rbcL sequences, we revealed a surprisingly high molecular diversity: 12 Arctic Zygnema genotypes and one Zygnemopsis genotype were found. In addition, we characterized individual Arctic genotypes based on cell width and chloroplast morphology using light and confocal laser scanning microscopy. Our findings highlight the importance of a molecular approach when working with sterile filamentous Zygnematophyceae, as hidden diversity might be very beneficial for adaptation to harsh environmental conditions, and experimental results could be misinterpreted when hidden diversity is neglected.

We have cloned and characterized a single copy C. reinhardtii gene containing an open reading frame of 333 nucleotides encoding a 12.7 kDa protein. The novel protein, DIP13, exhibits 60% identity with two mammalian proteins, human NA14 and an unnamed mouse protein. Homologous sequences are also present in several protozoan, trematode and fish genomes, but no homologs have been found in the completed genomes of yeast, Drosophila, C. elegans and A. thaliana. By using a specific antibody we have localized DIP13 to microtubule structures, namely basal bodies, flagellar axonemes and cytoplasmic microtubules. Anti-DIP13 antibody also specifically recognized human NA14 by immunofluorescence and stained basal bodies and flagella of human sperm cells as well as the centrosome of HeLa cells. Expression of the DIP13 open reading frame in antisense orientation in Chlamydomonas resulted in multinucleate, multiflagellate cells,which suggests a role for this protein in ensuring proper cell division. Thus,DIP13/NA14 could represent the founding members of a new class of highly conserved proteins that are associated with microtubule structures.

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 mm. 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.

Magnetically doped semiconducting topological insulators J. Appl. Phys. 112, 063912 (2012) Effect of the thickness of the MoO3 layers on optical properties of MoO3/Ag/MoO3 multilayer structures J. Appl. Phys. 112, 063505 (2012) Local conductivity and the role of vacancies around twin walls of (001)−BiFeO3 thin films We report on systematic study of photoluminescence properties of nanocrystalline titanium dioxide films consisting of predominantly anatase nanoparticles with diameters larger than 13 nm. We measured photoluminescence under two selected excitation wavelengths ͑325 nm/442 nm, i.e., above/below band gap excitation͒, under different values of ambient air pressure ͑5-10 5 Pa͒, and in the temperature interval 10-300 K. On basis of our results, we are able to distinguish two different processes leading to photoluminescence: the exciton recombination and the recombination of carriers in the energy states related to the surface of nanocrystals. We propose microscopic models describing well the effects of temperature and ambient conditions on photoluminescence of nanocrystalline titanium dioxide films.

The Watanabea clade of the Trebouxiophyceae included mostly unicellular coccoid microalgae that thrived in various terrestrial microhabitats. The diversity of these morphologically uniform microalgae was little known, and several new genus-level lineages had recently been described on the basis of molecular data. In this study, we provided a taxonomic description of a new trebouxiophycean genus, Parachloroidium, found in the Mediterranean in corticolous phototrophic biofilms. Their simple chlorelloid morphology did not unambiguously distinguish the Parachloroidium strains from other similar green algae. However, ultrastructural characteristics and molecular phylogenetic analyses based on the 18S ribosomal (r)DNA, internal transcribed spacer region (ITS) and the chloroplast ribulose-bisphosphate carboxylase gene sequences provided a basis for the discrimination of Parachloroidium from related genera of the Watanabea clade. The four strains investigated formed two species, P. laureanum and P. lobatum, which differed in plastid morphology and in ITS and 18S rDNA sequences. All four strains were characterized by globular or ellipsoidal cell shapes, single parietal plastids and asexual reproduction by autospores. Their plastids lacked typical pyrenoids; however, plastids included peculiar thylakoid-free regions of irregular shape. On the basis of accumulating molecular data, we concluded that the Watanabea clade was a diverse phylogenetic lineage within the subaerial chlorelloid green algae.

Ultrastructural examination of three glucosamine-type Chlorella species (C. vulgaris var. vulgaris, C. kessleri, C. sorokiniana), forming a related group in phylogenetic trees inferred from 18S rRNA gene sequences (FRIEDL 1995, Huss et al. 1999), revealed a similar cell ultrastructure but some differences in early and later stages of the cell wall development. All species mentioned above contain the monosaccharide glucosamine as the main constituent of the rigid cell wall (TAKEDA 1991, 1993a, 1993b). A thin electrondense layer is the first visible' structure covering the young daughter protoplasts of C. vulgaris and C. sorokiniana. Layered microfibrils can be observed in cross-sections of adult cell walls. Remnants of the broken maternal cell walls (MCW) persist in a culture medium. In C. kessleri the initial electrondense layer was not found. The cell wall is hardly visible, no rrricrofibrillar structure was detected. No MCW remnants were found in the medium. Negatively stained microfibrils of all the three species obtained by IN NaOH and 2M TFAA treatment are straight or slightly bent. The pyrenoid is transversed by two thylakoids. The rigid cell wall of C. luteoviridis is composed of glucose and mannose (TAKEDA 1991, 1993a, 1993b). However some ultrastructural features of C. luteoviridis resemble that of glucosamine-type cWorellas (the thin electrondense layer covering the young daughter protoplasts, microfibrillar structure of the adult cell wall visible on cross-sections, MCW remnants persisting in a medium). Microfibrils do not form a net, they are kinked and flexuous. C. luteoviridis differs from glucosamine-type species in the pyrenoid structure (the pyrenoid is bisected by four or two thylakoids). Thickness of microfibrils in all studied species is about 5 nm.