Katia Sciuto

Ulva (Chlorophyta, Ulvales) Biodiversity in the North Adriatic Sea (Mediterranean, Italy): Cryptic Species and New Introductions.

Ulva Linnaeus (Ulvophyceae, Ulvales) is a genus of green algae widespread in different aquatic environments. Members of this genus show a very simple morphology and a certain degree of phenotypic plasticity, heavily influenced by environmental conditions, making difficult the delineation of species by morphological features alone. Most studies dealing with Ulva biodiversity in Mediterranean waters have been based only on morphological characters and a modern taxonomic revision of this genus in the Mediterranean is not available. We report here the results of an investigation on the diversity of Ulva in the North Adriatic Sea based on molecular analyses. Collections from three areas, two of which subject to intense shipping traffic, were examined, as well as historical collections of Ulva stored in the Herbarium Patavinum of the University of Padova, Italy. Molecular analyses based on partial sequences of the rbcL and tufA genes revealed the presence of six different species, often with overlapping morphologies: U. californica Wille, U. flexuosa Wulfen, U. rigida C. Agardh, U. compressa Linnaeus, U. pertusa Kjellman, and one probable new taxon. U. californica is a new record for the Mediterranean and U. pertusa is a new record for the Adriatic. Partial sequences obtained from historical collections show that most of the old specimens are referable to U. rigida. No specimens referable to the two alien species were found among the old herbarium specimens. The results indicate that the number of introduced seaweed species and their impact on Mediterranean communities have been underestimated, due to the difficulties in species identification of morphologically simple taxa as Ulva.

Polyphasic approach and typification of selected Phormidium strains (Cyanobacteria)

Cyanobacteria (phylum Cyanophyta/Cyanobacteria, class Cyanophyceae) are among the most widespread organisms and are able to adapt themselves to different extreme environments. These micro‐organisms have an important ecological role, given their ability to perform oxygenic photosynthesis, and are employed in different fields based on their ability to produce several bioactive compounds. Their prokaryotic nature, the presence of many cryptic species, and the coexistence of different nomenclature systems make the taxonomic identification of cyanobacteria particularly difficult. Moreover, for several species, the original reference strains (holotypes) are lacking. Increasingly, authors are using a polyphasic approach to characterize cyanobacteria, while typification is a recent trend that is being used to solve the problem of missing holotypes in other micro‐organisms. Here we focus on a filamentous cyanobacterium, isolated from the Euganean Thermal District (Padova, Italy) and temporarily named strain ETS‐02, using a polyphasic approach that includes morphological, ultrastructural, biochemical (pigment and fatty acid content), physiological (nitrogen fixation), and genetic (16S rRNA, 16S–23S ITS, cpcB‐IGS‐cpcA, rpoC1, gyrB, rbcL, nifD loci) analyses. The description of Phormidium cf. irriguum CCALA 759 as the epitype of Phormidium irriguum was also used to complete the characterization of strain ETS‐02.

Polyphasic characterization of a thermo-tolerant filamentous cyanobacterium isolated from the Euganean thermal muds (Padua, Italy)

In this paper we report a morphological, ultrastructural, biochemical and molecular (16S rRNA, 16S–23S ITS, rbcL and rpoC1 gene sequencing) survey on a very thin, non-heterocystous, filamentous cyanobacterium, isolated from mats covering several mud maturation tanks of the Euganean Thermal District, at temperatures ranging from 26 to 59°C. Denaturing gradient gel electrophoresis results, obtained using cyanobacterial primers targeting the 16S rRNA gene, confirmed that this cyanobacterium is one of the commonest taxa growing in the mud tanks. Comparison with Geitlerinema sp. PCC 8501 (=Phormidium laminosum Gomont ex Gomont strain OH-1-p Cl 1), a thin thermobiotic species isolated from hot springs of Oregon and morphologically similar to our isolate, led us to hypothesize that the Euganean and PCC 8501 strains are either very similar sister species or ecotypes of the same species in a yet to be defined clade, clearly distinct within the paraphyletic Leptolyngbya group.

Cyanobacteria: the bright and dark sides of a charming group

Cyanobacteria are some of the oldest organisms known. Thanks to their photosynthetic apparatus, capable of splitting water into O2, protons, and electrons, this large and morphologically diverse group of phototrophic prokaryotes transformed Earth’s atmosphere to one suitable for aerobic metabolism and complex life. The long debated Endosymbiotic Theory attributes to cyanobacteria also a significant role in the evolution of life, as important players in plastid origin of higher plants and other photosynthetic eukaryotes. Recent molecular surveys are trying to understand how, exactly, cyanobacteria contributed to plant genome evolution. Their ancient origin and their widespread distribution have recently opened the possibility of including fossil cyanobacterial DNA into the palaeo-reconstructions of various environments and in the calibration of historical records. Cyanobacteria occur in almost every habitat on Earth and can be found in environments subject to stressful conditions, such as desert soils, glaciers, and hot springs. They are common also in urban areas, where they are involved in biodeterioration phenomena. Their great adaptability and versatility are due to a characteristic cell structure, with typical inclusions and particular envelopes. They are the most complex prokaryotes, since they are able to form filaments, colonies, and mats, and they exhibit distinctive ways of movements. To live in different environments, facing biotic and abiotic stresses, cyanobacteria produce also a large array of metabolites, which have potential applications in several fields, such as nutrition, medicine, and agriculture. They have also an important ecological role, not only as primary producers, but also because of their coexistence (often, but not exclusively, in the form of symbiosis) with other organisms to which they supply nitrogen. On the other side, cyanobacteria can have also a negative impact both on the environment and society. In particular they can release a range of toxic compounds, cyanotoxins, diverse in structure and in their effects on human and animal health. In spite of their importance, cyanobacterial identification is not always easy and the use of modern methods (e.g., molecular sequencing, cytomorphology, and ecophysiology) has led to the revision of traditional taxa and to the discovery of new ones. Currently, the most accepted method for cyanobacterial classification is a polyphasic approach, also including comparison with reference specimens. Moreover, several authors are making efforts to create a unique nomenclature system for cyanobacteria.

Photosynthesis in extreme environments: responses to different light regimes in the Antarctic alga Koliella antarctica

Antarctic algae play a fundamental role in polar ecosystem thanks to their ability to grow in an extreme environment characterized by low temperatures and variable illumination. Here, for prolonged periods, irradiation is extremely low and algae must be able to harvest light as efficiently as possible. On the other side, at low temperatures even dim irradiances can saturate photosynthesis and drive to the formation of reactive oxygen species. Colonization of this extreme environment necessarily required the optimization of photosynthesis regulation mechanisms by algal organisms. In order to investigate these adaptations we analyzed the time course of physiological and morphological responses to different irradiances in Koliella antarctica, a green microalga isolated from Ross Sea (Antarctica). Koliella antarctica not only modulates cell morphology and composition of its photosynthetic apparatus on a long-term acclimation, but also shows the ability of a very fast response to light fluctuations. Koliella antarctica controls the activity of two xanthophyll cycles. The first, involving lutein epoxide and lutein, may be important for the growth under very low irradiances. The second, involving conversion of violaxanthin to antheraxanthin and zeaxanthin, is relevant to induce a fast and particularly strong non-photochemical quenching, when the alga is exposed to higher light intensities. Globally K. antarctica thus shows the ability to activate a palette of responses of the photosynthetic apparatus optimized for survival in its natural extreme environment.

Detection of the new cosmopolitan genus Thermoleptolyngbya (Cyanobacteria, Leptolyngbyaceae) using the 16S rRNA gene and 16S–23S ITS region

Cyanobacteria are widespread prokaryotes that are able to live in extreme conditions such as thermal springs. Strains attributable to the genus Leptolyngbya are among the most common cyanobacteria sampled from thermal environments. Leptolyngbya is a character-poor taxon that was demonstrated to be polyphyletic based on molecular analyses. The recent joining of 16S rRNA gene phylogenies with 16S-23S ITS secondary structure analysis is a useful approach to detect new cryptic taxa and has led to the separation of new genera from Leptolyngbya and to the description of new species inside this genus and in other related groups. In this study, phylogenetic investigations based on both the 16S rRNA gene and the 16S-23S ITS region were performed alongside 16S rRNA and 16S-23S ITS secondary structure analyses on cyanobacteria of the family Leptolyngbyaceae. These analyses focused on filamentous strains sampled from thermal springs with a morphology ascribable to the genus Leptolyngbya. The phylogenetic reconstructions showed that the Leptolyngbya-like thermal strains grouped into a monophyletic lineage that was distinct from Leptolyngbya. The 16S-23S ITS secondary structure results supported the separation of this cluster. A new genus named Thermoleptolyngbya was erected to encompass these strains, and two species were described inside this new taxon: T. albertanoae and T. oregonensis.

Chodatodesmus australis sp. nov. (Scenedesmaceae, Chlorophyta) from Antarctica, with the emended description of the genus Chodatodesmus, and circumscription of Flechtneria rotunda gen. et sp. nov.

The family Scenedesmaceae is a taxonomically complicated group due to its simple morphology, high phenotypic plasticity, and the presence of cryptic taxa. Over the years several taxonomic revisions, based on molecular data, affected the family. Here, we describe a new scenedesmacean species from Antarctica, Chodatodesmus australis, based on phylogenetic analyses of data from nuclear (ITS2 spacer, 18S rDNA), and plastid (rbcL, tufA) markers. Morphological (LM and SEM) and ultrastructural (TEM) observations, carried out both on the holotype of C. australis and on the generitype of Chodatodesmus, allow us to emend the original generic description of this genus. Our molecular and phylogenetic data also reveal the existence of a new monotypic genus, Flechtneria, inside the family Scenedesmaceae and lead to the taxonomic reassignment of some microalgal strains available in International Culture Collections to new taxa. Of the considered genomic regions, the tufA gene was the easiest to amplify and sequence and it showed the highest phylogenetic signal, even if the number of sequences already available for this marker in the public databases was considerably lower than for the other chosen loci. The rbcL gene also provided good phylogenetic signal, but its amplification and sequencing were generally more problematic. The nuclear markers gave lower phylogenetic signals, but the 18S rDNA allowed distinction at the genus level and the ITS2 spacer had the advantage that secondary structures could be considered in the analyses. The use of more than one molecular locus is suggested to obtain reliable results in the characterization of scenedesmacean strains.

Gracilaria viridis sp. nov. (Gracilariales, Rhodophyta): a new red algal species from the Mediterranean Sea

Sfriso A., Wolf M.A., Sciuto K., Morabito M., Andreoli C. and Moro I. 2013. Gracilaria viridis sp. nov. (Gracilariales, Rhodophyta): a new red algal species from the Mediterranean Sea. Phycologia 52: 65–73. DOI: 10.2216/12-007.1 We characterized a new Gracilaria species from the Venice Lagoon, Italy, using molecular analyses based on the plastid large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase gene (rbcL) and the intergenic RuBisCO spacer (rbcL-rbcS), combined with morphology data. This new entity was recorded on the artificial substrata of the Venice Gulf from March to July, adding to 12 Gracilaria taxa already recorded in the Mediterranean and Adriatic seas. Thalli exhibited a green-yellowish pigmentation with pink shades, and there was dense branching in the distal portions. Tetrasporangia were scattered on thallus cortex and distributed mostly on short, stipitate branchlets. The inner pericarp was connected to the gonimoblast by tubular nutritive cells. The male gametophytic plants formed round-elliptical spermatangial verrucosa-type conceptacles. This species grew attached on artificial rocky substrata of the low midlittoral and upper sublittoral zone in spring and early summer. Molecular analyses based on the plastid-encoded rbcL gene showed a 99.66% nucleotide identity with another Gracilaria sp. from southern Sicily. We compared our rbcL-rbcS spacer sequences with those of two cryptic species, and the phylogenetic analyses confirmed that the Venice populations were a new species. We suggested that the discovery of this new species was not due to an extra-Mediterranean introduction but the consequence of its misidentification as Gracilaria gracilis, which has a similar gross morphology.

Cryptic Cyanobacterial Diversity in the Giant Cave (Trieste, Italy): The New Genus Timaviella (Leptolyngbyaceae)

Abstract The microflora of hypogean environments has been studied increasingly worldwide. However, some sites have hardly been examined or not studied at all; this is the case for the Giant Cave, a Karst show cave located near Trieste, Italy. In the present study we began characterizing the Giant Cave Lampenflora by using a polyphasic approach, focusing, in particular, on three Leptolyngbya-like strains named GR2, GR4, and GR13. Light and electron microscopic observations were carried out and the water-soluble pigment composition was analysed. Phylogenetic reconstruction, based on the 16S rRNA gene and the 16S-23S ITS region, was performed to better understand the taxonomic position of these strains, complemented by 16S-23S ITS secondary structure analysis. Ecological and geographical data for the investigated strains and for the other cyanobacterial strains grouping with them in the phylogenetic reconstructions were also considered. Based on the results, strain GR2 was ascribed to the species Heteroleibleinia purpurascens (Hansgirg) Anagnostidis & Komárek; strains GR4 and GR13 were attributed to a new genus of the family Leptolyngbyaceae, Timaviella Sciuto & Moro, gen. nov., and represented two distinct species: Timaviella circinata Sciuto & Moro and Timaviella karstica Sciuto & Moro.

Problems and solutions in Gracilaria systematics: an example from G. bursa pastoris (Gmelin) Silva.

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