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Cyanobacteria inhabiting lotic environments have been poorly studied and characterized in Mexico, despite their potential risks from cyanotoxin production. This article aims to fill this knowledge gap by assessing the importance of benthic cyanobacteria as potential cyanotoxin producers in central Mexican rivers through: (i) the taxonomic identification of cyanobacteria found in these rivers, (ii) the environmental characterization of their habitats, and (iii) testing for the presence of toxin producing genes in the encountered taxa. Additionally, we introduce and discuss the use of the term "CyanoHAMs" for lotic water environments. Populations of cyanobacteria were collected from ten mountain rivers and identified using molecular techniques. Subsequently, these taxa were evaluated for genes producing anatoxins and microcystins via PCR. Through RDA analyses, the collected cyanobacteria were grouped into one of three categories based on their environmental preferences for the following: (1) waters with high ionic concentrations, (2) cold-temperate waters, or (3) waters with high nutrient enrichment. Populations from six locations were identified to genus level: Ancylothrix sp., Cyanoplacoma sp., and Oxynema sp. The latter was found to contain the gene that produces anatoxins and microcystins in siliceous rivers, while Oxynema tested positive for the gene that produces microcystins in calcareous rivers. Our results suggest that eutrophic environments are not necessarily required for toxin-producing cyanobacteria. Our records of Compactonostoc, Oxynema, and Ancylothrix represent the first for Mexico. Four taxa were identified to species level: Wilmottia aff. murrayi, Nostoc tlalocii, Nostoc montejanii, and Dichothrix aff. willei, with only the first testing positive using PCR for anatoxin and microcystin-producing genes in siliceous rivers. Due to the differences between benthic growths with respect to planktonic ones, we propose the adoption of the term Cyanobacterial Harmful Algal Mats (CyanoHAMs) as a more precise descriptor for future studies.

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As the taxonomic knowledge of cyanobacteria from terrestrial environments increases, it remains important to analyze biodiversity in areas that have been understudied to fully understand global and endemic diversity. This study was completed as part of a larger algal biodiversity study of the soil biocrusts of San Nicholas Island, California, USA. Among the taxa isolated were several new species in three genera (Atlanticothrix, Pycnacronema, and Konicacronema) which were described from, and previously restricted to, Brazil. New taxa are described herein using a polyphasic approach to cyanobacterial taxonomy that considers morphological, molecular, ecological, and biogeographical factors. Morphological data corroborated by molecular analysis including sequencing of the 16S rRNA gene, and the associated 16S-23S ITS rRNA region was used to delineate three new species of Atlanticothrix, two species of Pycnacronema, and one species of Konicacronema. The overlap of genera from San Nicolas Island and Brazil suggests that cyanobacterial genera may be widely distributed across global hemispheres, whereas the presence of distinct lineages may indicate that this is not true at the species level. Our data suggest that based upon global wind patterns, cyanobacteria in both Northern and Southern hemispheres of the Americas may have a more recent common ancestor in Northern Africa, but this common ancestry is distant enough that speciation has occurred since transatlantic dispersal.

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Zea mays var. amylacea and Zea mays var. indurata are maize ecotypes from Paraguay. Aspergillus section Flavi is the main spoilage fungus of maize under storage conditions. Due to its large intraspecific genetic variability, the accurate identification of this fungal taxonomic group is difficult. In the present study, potential mycotoxigenic strains of Aspergillus section Flavi isolated from Z. mays var. indurata and Z. mays var. amylacea that are marketed in the metropolitan region of Asunción were identified by a polyphasic approach. Based on morphological characters, 211 isolates were confirmed to belong to Aspergillus section Flavi. A subset of 92 strains was identified as Aspergillus flavus by mass spectrometry MALDI-TOF and the strains were classified by MALDI-TOF MS into chemotypes based on their aflatoxins and cyclopiazonic acid production. According to the partial sequencing of ITS and CaM genes, a representative subset of 38 A. flavus strains was confirmed. Overall, 75 A. flavus strains (86%) were characterized as producers of aflatoxins. The co-occurrence of at least two mycotoxins (AF/ZEA, FUM/ZEA, and AF/ZEA/FUM) was detected for five of the Z. mays samples (63%). Considering the high mycological bioburden and mycotoxin contamination, maize marketed in the metropolitan region of Asunción constitutes a potential risk to food safety and public health and requires control measures.

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The taxonomy of coccoid cyanobacteria, such as Chroococcidiopsis, Pleurocapsa, Chroococcus, Gloeothece, Gloeocapsa, Gloeocapsopsis, and the related recent genera Sinocapsa and Aliterella, can easily be intermixed when solely compared on a morphological basis. There is still little support on the taxonomic position of some of the addressed genera, as genetic information is available only for a fraction of species that have been described solely on morphology. Modern polyphasic approaches that combine classic morphological investigations with DNA-based molecular analyses and the evaluation of ecological properties can disentangle these easily confusable unicellular genera. By using such an approach, we present here the formal description of two novel unicellular cyanobacterial species that inhabit the Coastal Range of the Atacama Desert, Gloeocapsopsis dulcis (first reported as Gloeocapsopsis AAB1) and Gloeocapsopsis diffluens. Both species could be clearly separated from previously reported species by 16S rRNA and 16S-23S ITS gene sequencing, the resulting secondary structures, p-distance analyses of the 16S-23S ITS, and morphology. For avoiding further confusions emendation of the genus Gloeocapsopsis as well as epitypification of the type species Gloeocapsopsis crepidinum based on the strain LEGE06123 were conducted.

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Snow algae play crucial roles in cold ecosystems, however, many aspects related to their biology, adaptations and especially their diversity are not well known. To improve the identification of snow algae from colored snow, in the present study we used a polyphasic approach to describe a new Antarctic genus, Chlorominima with the species type Chlorominima collina. This new taxon was isolated of colored snow collected from the Collins Glacier (King George Island) in the Maritime Antarctic region. Microscopy revealed biflagellated ellipsoidal cells with a rounded posterior end, a C-shaped parietal chloroplast without a pyrenoid, eyespot, and discrete papillae. Several of these characteristics are typical of the genus Chloromonas, but the new isolate differs from the described species of this genus by the unusual small size of the cells, the presence of several vacuoles, the position of the nucleus and the shape of the chloroplast. Molecular analyzes confirm that the isolated alga does not belong to Chloromonas and therefore forms an independent lineage, which is closely related to other unidentified Antarctic and Arctic strains, forming a polar subclade in the Stephanosphaerinia phylogroup within the Chlamydomonadales. Secondary structure comparisons of the ITS2 rDNA marker support the idea that new strain is a distinct taxon within of Caudivolvoxa. Physiological experiments revealed psychrophilic characteristics, which are typical of true snow algae. This status was confirmed by the partial transcriptome obtained at 2°C, in which various cold-responsive and cryoprotective genes were identified. This study explores the systematics, cold acclimatization strategies and their implications for the Antarctic snow flora.

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Cyanobacteria are crucial ecosystem components in dryland soils. Advances in describing α-level taxonomy are needed to understand what drives their abundance and distribution. We describe Trichotorquatus gen. nov. (Oculatellaceae, Synechococcales, Cyanobacteria) based on four new species isolated from dryland soils including the coastal sage scrub near San Diego, California (USA), the Mojave and Colorado Deserts with sites at Joshua Tree National Park and Mojave National Preserve, California (USA), and the Atacama Desert (Chile). The genus is morphologically characterized by having thin trichomes (<4.5 µm wide), cells both shorter and longer than wide, rarely occurring single and double false branching, necridia appearing singly or in rows, and sheaths with a distinctive collar-like fraying and widening mid-filament, the feature for which the genus is named. The genus is morphologically nearly identical with Leptolyngbya sensu stricto but is phylogenetically quite distant from that genus. It is consequently a cryptic genus that will likely be differentiated in future studies based on 16S rRNA sequence data. The type species, T. maritimus sp. nov. is morphologically distinct from the other three species, T. coquimbo sp. nov., T. andrei sp. nov. and T. ladouxae sp. nov. However, these latter three species are morphologically very close and are considered by the authors to be cryptic species. All species are separated phylogenetically based on sequence of the 16S-23S ITS region. Three distinct ribosomal operons were recovered from the genus, lending difficulty to recognizing further diversity in this morphologically cryptic genus.

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The polyphasic approach has been widely applied in cyanobacterial taxonomy, which frequently led to additions to the species inventory. Increasing our knowledge about species and the habitats they were isolated from enables new insights into the ecology of newly established genera and species allowing speculations about the ecological niche of taxa. Here, we are describing three new species belonging to three genera that broadens the ecological amplitude and the geographical range of each of the three genera. Cyanocohniella crotaloides sp. nov. is described from sandy beach mats of the temperate island Schiermonnikoog, Netherlands, Oculatella crustae-formantes sp. nov. was isolated from biological soil crusts of the Arctic Spitsbergen, Norway, and Aliterella chasmolithica originated from granitic stones of the arid Atacama Desert, Chile. All three species could be separated from related species using molecular sequencing of the 16S rRNA gene and 16S-23S ITS gene region, the resulting secondary structures as well as p-distance analyses of the 16S-23S ITS and various microscopic techniques. The novel taxa described in this study contribute to a better understanding of the diversity of the genera Cyanocohniella, Oculatella, and Aliterella in different habitats.

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Soil cyanobacteria are crucial components of biological soil crusts and carry out many functions in dryland ecosystems. Despite this importance, their taxonomy and population genetics remain poorly known. We isolated 42 strains of simple filamentous cyanobacteria previously identified as Pseudophormidium hollerbachianum from 26 desert locations in the North and South America and characterized these strains using a total evidence approach, that is, using both morphological and molecular data to arrive at taxonomic decisions. Based on a phylogenetic analysis of 16S rRNA gene sequences, we propose and characterize Myxacorys gen. nov. with two new species Myxacorys chilensis, the generitype, and M. californica. We also found distinct 16S-23S ITS sequence variability within species in our dataset. Especially interesting was the presence of two distinct lineages of M. californica obtained from locations in close spatial proximity (within a few meters to kilometers from each other) suggesting niche differentiation. The detection of such unrecognized lineage-level variability in soil cyanobacteria has important implications for biocrust restoration practices and conservation efforts.

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Cyanobacteria is an ancient phylum of oxygenic photosynthetic microorganisms found in almost all environments of Earth. In recent years, the taxonomic placement of some cyanobacterial strains, including those belonging to the genus Nostocsensu lato, have been reevaluated by means of a polyphasic approach. Thus, 16S rRNA gene phylogeny and 16S-23S internal transcribed spacer (ITS) secondary structures coupled with morphological, ecological and physiological data are considered powerful tools for a better taxonomic and systematics resolution, leading to the description of novel genera and species. Additionally, underexplored and harsh environments, such as saline-alkaline lakes, have received special attention given they can be a source of novel cyanobacterial taxa. Here, a filamentous heterocytous strain, Nostocaceae CCM-UFV059, isolated from Laguna Amarga, Chile, was characterized applying the polyphasic approach; its fatty acid profile and physiological responses to salt (NaCl) were also determined. Morphologically, this strain was related to morphotypes of the Nostocsensu lato group, being phylogenetically placed into the typical cluster of the genus Desmonostoc. CCM-UFV059 showed identity of the 16S rRNA gene as well as 16S-23S secondary structures that did not match those from known described species of the genus Desmonostoc, as well as distinct ecological and physiological traits. Taken together, these data allowed the description of the first strain of a member of the genus Desmonostoc from a saline-alkaline lake, named Desmonostoc salinum sp. nov., under the provisions of the International Code of Nomenclature for algae, fungi and plants. This finding extends the ecological coverage of the genus Desmonostoc, contributing to a better understanding of cyanobacterial diversity and systematics.

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A novel actinobacterium, designated strain CMAA 1533T, was isolated from the rhizosphere of Deschampsia antarctica collected at King George Island, Antarctic Peninsula. Strain CMAA 1533T was found to grow over a wide range of temperatures (4-28 °C) and pH (4-10). Macroscopically, the colonies were observed to be circular shaped, smooth, brittle and opaque-cream on most of the culture media tested. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CMAA 1533T belongs to the family Nocardiaceae and forms a distinct phyletic line within the genus Rhodococcus. Sequence similarity calculations indicated that the novel strain is closely related to Rhodococcus degradans CCM 4446T, Rhodococcus erythropolis NBRC 15567T and Rhodococcus triatomae DSM 44892T (≤ 96.9%). The organism was found to contain meso-diaminopimelic acid, galactose and arabinose in whole cell hydrolysates. Its predominant isoprenologue was identified as MK-8(H2) and the polar lipids as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides. The major fatty acids were identified as Summed feature (C16:1 ω6c and/or C16:1 ω7c), C16:0, C18:1 ω9c and 10-methyl C18:0. The G+C content of genomic DNA was determined to be 65.5 mol%. Unlike the closely related type strains, CMAA 1533T can grow at 4 °C but not at 37 °C and was able to utilise adonitol and galactose as sole carbon sources. Based on phylogenetic, chemotaxonomic and physiological data, it is concluded that strain CMAA 1533T (= NRRL B-65465T = DSM 104532T) represents a new species of the genus Rhodococcus, for which the name Rhodococcus psychrotolerans sp. nov. is proposed.

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Brazil has an extensive and environmentally diverse coastline, which favors the occurrence of numerous cyanobacterial morpho- and ecotypes. Nevertheless, this coastline is still poorly studied and its diversity is underestimated. Considering the family Oscillatoriaceae, Lyngbya deserves special attention. It includes many clades which are phylogenetically non-related but morphologically similar. Such clades occur in marine and freshwater environments and are traditionally treated as a single genus. In the current study, we sampled both mediolittoral and estuarine zones along the Brazilian coast. Based on a polyphasic characterization, we described a new genus of marine filamentous cyanobacteria: Neolyngbya. It includes six new species sampled in Brazil, which are described in this study (N. maris-brasilis, N. granulosa, N. irregularis, N. nodulosa, N. arenicola and N. tenuis). Additionally, the characterization included a Neolyngbya sp. from Japan in the clade, but only based on molecular data. All species presented irregular arrangement of thylakoids as described for Oscillatoriaceae. The new genus shares morphological characteristics with species in different clades of the Lyngbya complex. The ultrastructural analyses of Neolyngbya, however, showed numerous gas vesicles, especially in the interthylakoid space; such feature is not observed in benthic Lyngbya species. Neolyngbya formed a well-supported clade (16S rRNA phylogeny), however distantly related to L. aestuarii and L. confervoides, both marine species clusters. The Limnoraphis clade is in a sister relationship to the Neolyngbya clade, however the former occurs in freshwater plankton. Secondary structures of 16S-23S rRNA ITS sequences were congruent with the phylogeny. The polyphasic characterization was helpful to clarify the diversity and ecological aspects of benthic filamentous cyanobacteria and the evolutionary history of the group. This favors a better understanding of inter and infrageneric taxa. The number of novel taxa described in this study emphasizes the importance of conducting additional floristic surveys, mainly in underexplored marine environments, to reveal the real cyanobacterial biodiversity in these areas.

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Small-spored Alternaria have been isolated from a wide variety of food crops, causing both economic losses and human health risk due to the metabolites produced. Their taxonomy has been discussed widely, but no scientific consensus has been established in this field to date. Argentina is a major exporter of agricultural products, so it is essential to thoroughly understand the physiological behaviour of this pathogen in a food safety context. Thus, the objective of this work was to characterize small-spored Alternaria spp. obtained from tomato fruits, pepper fruits, wheat grains and blueberries from Argentina by a polyphasic approach involving metabolomic and phylogenetic analyses based on molecular and morphological characters. Morphological analysis divided the population studied into three groups; A. arborescens sp.-grp., A. tenuissima sp.-grp., and A. alternata sp.-grp. However, when these characters were simultaneously analysed with molecular data, no clearly separated groups were obtained. Haplotype network and phylogenetic analysis (both Bayesian and maximum parsimony) of a conserved region yielded the same result, suggesting that all isolates belong to the same species. Furthermore, no correlation could be established between morphological species-groups and a metabolite or group of metabolites synthesized. Thus, the whole set of analyses carried out in the present work supports the hypothesis that these small-spored Alternaria isolates from food belong to the same species. Identification at species level through classical morphology or modern molecular techniques does not seem to be a useful tool to predict toxicological risk in food matrices. The detection of any small-spored Alternaria from Section Alternaria (D.P. Lawr., Gannibal, Peever & B.M. Pryor 2013) in food implies a potential toxicological risk.

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Saline-alkaline lakes are extreme environments that limit the establishment and development of life. The Nhecolândia, a subregion of the Pantanal wetland in Brazil, is characterized by the existence of ~500 saline-alkaline lakes, which support an underexplored and rich diversity of microorganisms. In this study, unicellular and homocytous cyanobacteria from five saline-alkaline lakes were accessed by culture-dependent approaches. Morphological evaluation and analyses of near complete sequences (~1400 nt) of the 16S rRNA genes were applied for phylogenetic and taxonomic placement. This polyphasic approach allowed for the determination of the taxonomic position of the isolated strains into the following genera: Cyanobacterium, Geminocystis, Phormidium, Leptolyngbya, Limnothrix, and Nodosilinea. In addition, fourteen Pseudanabaenales and Oscillatoriales representatives of putative novel taxa were found. These sequences fell into five new clades that could correspond to new generic units of the Pseudanabaenaceae and Phormidiaceae families.