Search

Chrysophytes are a diverse group of stramenopile protists comprising a variety of taxa with different cell organizations. Here, we morphologically and genetically characterize a novel chrysophyte genus isolated from three freshwater localities in the Czech Republic, described as Globulochrysis compacta gen. nov. sp. nov. The genus is well characterized by the frequent formation of closely packed cells, developing into large, spherical sporangia. This alga also forms solitary cells, mucilaginous colonies, amoebae, and teardrop-shaped zoids. We also investigated the morphologically similar genus Chrysotilos, isolated from its type locality in the Austrian Alps. In culture, Chrysotilos showed characteristic neustonic growth, which was, however, not observed in Globulochrysis. Phylogenetic analyses based on 18S rRNA and rbcL genes showed that these two algae belong to two distinct lineages. Whereas Chrysotilos was inferred within the clade Hibberdiales, Globulochrysis formed a completely new lineage within the order Hydrurales. Globulochrysis is described as a new genus in Hydrurales, Chrysophyceae. The genus is characterized by closely packed cells. The phylogenetic position of neustonic Chrysotilos is determined. [ABSTRACT FROM AUTHOR]

We present a synopsis of studies reporting the free-living occurrence of green algal lichen symbionts. We give an overview of all known lichen photobiont genera together with comprehensive descriptions, taxonomical classification and occurrence data. Based on the analysis of 310 records, we discovered that at least 80% of lichen photobiont genera were observed in the free-living state. Diplosphaera chodatii, Elliptochloris bilobata and Chloroidium ellipsoideum represent both morphologically and genetically the most frequently reported free-living photobiont species. Trebouxia, the most prevalent genus of lichen photobionts, has frequently been reported to exist independently to fungal hyphae. Based on our literature survey, free-living photobionts of lichens are able to grow in a wide range of environments and substrates, with most records coming from soil and biological soil crusts. [ABSTRACT FROM AUTHOR]

Morphological and ultrastructural investigations are crucial for the identification and characterization of species such as microalgae, microorganisms that greatly change their morphology and physiology during their life cycle. Transmission electron microscopy (TEM) is an excellent tool for the ultrastructural observation of cells and their components. To date, limited ultrastructural studies have been carried out on microalgae, due to the difficulties in sample preparation. The aim of this work is to establish an appropriate fixation method that allows to better preserve the algal ultrastructure and test the suitability of the thawed algae for TEM observation. Fresh and thawed algae (Coccomyxa melkonianii SCCA 048) were fixed with different TEM fixation methods (a mix of glutaraldehyde and paraformaldehyde for several incubation times, sometimes preceded by a prefixation in cold methanol). The ultrastructural images obtained from fresh algae were compared to those obtained from frozen biomass. The best morphological results were achieved by fixing fresh algae in 1% paraformaldehyde and 1.25% glutaraldehyde for 5 hr. Pretreating with frozen methyl alcohol reduced fixation time to 2 hr. Both fresh and frozen algae ultrastructure were rather well preserved also with 1% paraformaldehyde and 1.25% glutaraldehyde for 2 hr. Ultrastuctural morphological images of the thawed algae demonstrated that also frozen samples can be used in TEM research, widening specimen suitability by means of this technique. [ABSTRACT FROM AUTHOR]

The effects of nitrogen concentration and pH on the growth kinetics of the extremophile microalgal strain Coccomyxa melkonianii SCCA 048 in multiwell and batch photobioreactors are investigated in this work. Moreover, the experimental results were successfully interpreted by a simple, mathematical model which represents a starting point towards the development of a suitable tool for the design, control, and optimization of large scale photobioreactors where C. melkonianii would be cultivated. On the basis of fatty acids methyl esters (FAMEs) profile, potential properties of biodiesel have been predicted through suitable software. [ABSTRACT FROM AUTHOR]

The extremophile green alga Coccomyxa melkonianii SCCA 048 was investigated to evaluate its ability to grow in culture media with different pH. Specifically, Coccomyxa melkonianii was sampled in the Rio Irvi river (Sardinia, Italy) which is severely polluted by heavy metals as a result of abandoned mining activities. In this study, the strain was cultivated in growth media where the pH was kept fixed at the values of 4.0, 6.8 and 8.0, respectively. During the investigation, a significant phenotypic plasticity of this strain was observed. The strain grew well in the pH range 4.0-8.0, while the optimal value for its growth was 6.8. Furthermore, maximum lipid contents of about 24 and 22 %wt were achieved at the end of cultivation when using pH 4.0 and 8.0, respectively. Finally, the analysis of fatty acid methyl esters (FAMEs) highlights the presence of suitable amounts of compounds which can be profitably exploited in the food, nutraceutical, and cosmetic industry. This aspect, coupled with the possibility of cultivating Coccomyxa melkonianii under extreme pH conditions in economic open ponds, makes this strain an interesting candidate for several biotechnological applications. [ABSTRACT FROM AUTHOR]

In the present study, three new strains of the rare volvocalean green alga Lobomonas were isolated from field‐collected samples, one from Sardinia (Italy) and two from Argentina, and comparatively studied. The Sardinian and one of the Argentinian strains were identified as Lobomonas francei, the type species of the genus, whereas the second Argentinian strain corresponded to L. panduriformis. Two additional nominal species of Lobomonas from culture collections (L. rostrata and L. sphaerica) were included in the analysis and shown to be morphologically and molecularly identical to the L. francei strains. The presence, number, and shapes of cell wall lobes, the diagnostic criterion of Lobomonas, were shown to be highly variable depending on the chemical composition of the culture medium used. The analyses by SEM gave evidence that the cell wall lobes in Lobomonas originate at the junctions of adjacent cell wall plates by extrusion of gelatinous material. The four L. francei strains had identical nrRNA gene sequences and differed by only one or two substitutions in the ITS1 + ITS2 sequences. In the phylogenetic analyses, L. francei and L. panduriformis were sister taxa; however, another nominal Lobomonas species (L. monstruosa) did not belong to this genus. Lobomonas, together with taxa designated as Vitreochlamys, Tetraspora, and Paulschulzia, formed a monophyletic group that in the combined analyses was sister to the “Chlamydomonas/Volvox‐clade.” Based on these results, Lobomonas was revised, the diagnosis of the type species emended, a lectotype and an epitype designated, and several taxa synonymized with the type species. [ABSTRACT FROM AUTHOR]

The complete nucleotide sequences of the mitochondrial (mtDNA) and chloroplast (cpDNA) genomes ofChlorella variabilisNC64A (Trebouxiophyceae) have been determined in this study (GenBank accession no. KP271968 and KP271969, respectively). The mt genome assembles as a circle of 78,500 bp and contains 62 genes, including 32 protein-coding, 27 tRNA and 3 rRNA genes. The overall GC content is 28.2%, while the coding sequence is 34%. The cp genome forms a circle of 124,793 bp, containing 114 genes, including 79 protein-coding, 32 tRNA and 3 rRNA genes. The overall GC content is 33,9%, while the coding sequence is 50%. [ABSTRACT FROM AUTHOR]

The complete sequence of mitochondrial genome of theChlorella sorokinianastrain (SAG 111-8 k) is presented in this work. Within theChlorellagenus, it represents the second species with a complete sequenced and annotated mitochondrial genome (GenBank accession no. KM241869). The genome consists of circular chromosomes of 52,528 bp and encodes a total of 31 protein coding genes, 3 rRNAs and 26 tRNAs. The overall AT contents of theC. sorokinianamtDNA is 70.89%, while the coding sequence is of 97.4%. [ABSTRACT FROM AUTHOR]

The complete chloroplast genome sequence ofChlorella sorokinianastrain (SAG 111–8 k) is presented in this study. The genome consists of circular chromosomes of 109,811 bp, which encode a total of 109 genes, including 74 proteins, 3 rRNAs and 31 tRNAs. Moreover, introns are not detected and all genes are present in single copy. The overall AT contents of theC. sorokinianacpDNA is 65.9%, the coding sequence is 59.1% and a large inverted repeat (IR) is not observed. [ABSTRACT FROM AUTHOR]

Morphological and ultrastructural investigations are crucial for the identification and characterization of species such as microalgae, microorganisms that greatly change their morphology and physiology during their life cycle. Transmission electron microscopy (TEM) is an excellent tool for the ultrastructural observation of cells and their components. To date, limited ultrastructural studies have been carried out on microalgae, due to the difficulties in sample preparation. The aim of this work is to establish an appropriate fixation method that allows to better preserve the algal ultrastructure and test the suitability of the thawed algae for TEM observation. Fresh and thawed algae (Coccomyxa melkonianii SCCA 048) were fixed with different TEM fixation methods (a mix of glutaraldehyde and paraformaldehyde for several incubation times, sometimes preceded by a prefixation in cold methanol). The ultrastructural images obtained from fresh algae were compared to those obtained from frozen biomass. The best morphological results were achieved by fixing fresh algae in 1% paraformaldehyde and 1.25% glutaraldehyde for 5 hr. Pretreating with frozen methyl alcohol reduced fixation time to 2 hr. Both fresh and frozen algae ultrastructure were rather well preserved also with 1% paraformaldehyde and 1.25% glutaraldehyde for 2 hr. Ultrastuctural morphological images of the thawed algae demonstrated that also frozen samples can be used in TEM research, widening specimen suitability by means of this technique., (© 2020 Wiley Periodicals LLC.)

The complete sequence of mitochondrial genome of the Chlorella sorokiniana strain (SAG 111-8 k) is presented in this work. Within the Chlorella genus, it represents the second species with a complete sequenced and annotated mitochondrial genome (GenBank accession no. KM241869). The genome consists of circular chromosomes of 52,528 bp and encodes a total of 31 protein coding genes, 3 rRNAs and 26 tRNAs. The overall AT contents of the C. sorokiniana mtDNA is 70.89%, while the coding sequence is of 97.4%.

The complete chloroplast genome sequence of Chlorella sorokiniana strain (SAG 111-8 k) is presented in this study. The genome consists of circular chromosomes of 109,811 bp, which encode a total of 109 genes, including 74 proteins, 3 rRNAs and 31 tRNAs. Moreover, introns are not detected and all genes are present in single copy. The overall AT contents of the C. sorokiniana cpDNA is 65.9%, the coding sequence is 59.1% and a large inverted repeat (IR) is not observed.