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El sistema de inmunidad adaptativa en bacterias y arqueas, encargado de reconocer las secuencias de DNA invasores, se caracteriza por tener grupos de secuencias palindrómicas cortas repetidas e intercaladas de manera regular por espaciadores (CRISPR). Las proteínas asociadas a CRISPR (Cas) y los RNAs guías complementarios a secuencias específicas del DNA blanco constituyen una de las herramientas de edición genética más utilizadas para modificar a los organismos. En los últimos años se ha incrementado la variedad de los sistemas CRISPR/Cas, adaptándose a microorganismos como las levaduras, que cuentan con potencial biotecnológico. El objetivo de esta revisión es facilitar la comprensión de los conceptos básicos del sistema CRISPR/Cas9 y reconocer algunas de las variedades de esta herramienta molecular que se han implementado de manera exitosa en distintas levaduras. Asimismo, se describen varias de las nuevas tecnologías basadas en CRISPR que están revolucionando la investigación.

A number of heterocytous, mat-forming, tapering cyanobacteria in Rivulariaceae have recently been observed in both the Atlantic and Pacific coasts in the rocky intertidal and supratidal zones. These belong to the genera Nunduva, Kyrtuthrix, and Phyllonema and have been the subject of several recent studies. Herein, two new species of Nunduva (N. komarkovae and N. sanagustinensis) and two new species of Kyrtuthrix (K. munecosensis and K. totonaca) are characterized and described from the coasts of Mexico. Genetic separation based on the 16S-23S ITS region was pronounced (>10% in all comparisons). Morphological differences between all existing species in these two genera were also observed, but the group is morphologically complex, and these taxa are considered pseudocryptic. Nunduva and Kyrtuthrix remain morphologically and phylogenetically separate even with the addition of new species. However, how long will this remain the case? Many new genera and species of cyanobacteria have recently been described. Will the taxonomy of cyanobacteria eventually become saturated? Will we start to see multiple populations for the same cryptic species, or will future taxonomists collapse multiple species into fewer species, or multiple genera into single genera. The description of even more Nunduva and Kyrtuthrix species causes us to pause and evaluate the future of cyanobacterial taxonomy. These same questions are faced by algal taxonomists studying other phyla, and the resolution may ultimately be similar.

Las levaduras son organismos microscópicos que están distribuidos en toda la Tierra, de modo que algunas han adaptado su metabolismo para proliferar en ambientes extremos. Las levaduras que habitan en la Antártica son un grupo de microorganismos adaptados al frío que han sido poco estudiadas. En esta revisión se describen algunas de las adaptaciones metabólicas que les permiten habitar en ambientes extremos, por ejemplo, el de la Antártica. También se abordan las consideraciones relevantes para saber si una levadura es extremófila, así como los criterios utilizados para clasificar a las levaduras por crecimiento y temperatura. Además, se explica el papel de las vías de biosíntesis de carotenoides y lípidos que están involucradas en contrarrestar a las especies reactivas de oxígeno generadas por estrés oxidante en levaduras pigmentadas y oleaginosas del género Rhodotorula. La revisión también considera aspectos de investigación básica y la importancia de las levaduras oleaginosas de la Antártica para el desarrollo de algunas aplicaciones biotecnológicas.

The function of catalases A and T from the budding yeast Saccharomyces cerevisiae (ScCta1 and ScCtt1) is to decompose hydrogen peroxide (H2O2) to mitigate oxidative stress. Catalase orthologs are widely found in yeast, suggesting that scavenging H2O2 is crucial to avoid the oxidative damage caused by reactive oxygen species (ROS). However, the function of catalase orthologs has not yet been experimentally characterized in vivo. Here, we heterologously expressed Debaryomyces hansenii DhCTA1 and DhCTT1 genes, encoding ScCta1 and ScCtt1 orthologs, respectively, in a S. cerevisiae acatalasemic strain (cta1Δ ctt1Δ). We performed a physiological analysis evaluating growth, catalase activity, and H2O2 tolerance of the strains grown with glucose or ethanol as carbon source, as well as under NaCl stress. We found that both genes complement the catalase function in S. cerevisiae. Particularly, the strain harboring DhCTT1 showed improved growth when ethanol was used as carbon source both in the absence or presence of salt stress. This phenotype is attributed to the high catalase activity of DhCtt1 detected at the exponential growth phase, which prevents intracellular ROS accumulation and confers oxidative stress resistance.

Several populations of a non-tapering and tapering, fasciculated, single and geminate false branching heterocytous cyanobacterium were collected from rocky shores in the Pacific Ocean and Gulf of Mexico. The populations were provisionally placed in Brasilonema based on morphology, but upon sequencing of both environmental and culture material it was discovered that the populations/cultures belonged to the Rivulariaceae, in a marine subclade of the family containing Kyrtuthrix huatulcensis. In culture, the taxon exhibited tapering in isopolar filaments, providing further evidence that it was a member of the rivulariacean clade. Based on molecular data for other cyanobacteria within the rivulariacean clade, we identified at least three more species morphologically distinguishable from the Brasilonema-like material, all of which show more pronounced tapering. These cyanobacteria include not only tropical marine strains, but also a strain isolated from the English coastline in the Atlantic Ocean. We propose a new genus and four species for members of this distinctive clade, Nunduva fasciculata gen. nov., sp. nov., N. kania sp. nov., N. biania sp. nov., and N. britannica sp. nov. Other strains that others and we have isolated are sister to Nunduva and may eventually be placed within this genus, but at present, we consider the evidence for inclusion in Nunduva to be insufficient.

A population of Desertifilum (Cyanobacteria, Oscillatoriales) from an oligotrophic desertic biotope was isolated and characterized using a polyphasic approach including molecular, morphological, and ecological information. The population was initially assumed to be a new species based on ecological and biogeographic separation from other existing species, however, phylogenetic analyses based on sequences of the 16S rRNA gene and 16S-23S ITS region, placed this strain clearly within the type species, Desertifilum tharense. Comparative analysis of morphology, 16S rRNA gene similarity, 16S-23S ITS secondary structure, and percent dissimilarity of the ITS regions for all characterized strains supports placing the six Desertifilum strains (designated as PD2001/TDC17, UAM-C/S02, CHAB7200, NapGTcm17, IPPAS B-1220, and PMC 872.14) into D. tharense. The recognition of Desertifilum salkalinema and Desertifilum dzianense is not supported, although our analysis does support continued recognition of Desertifilum fontinale. Pragmatic criteria for recognition of closely related species are proposed based on this study and others, and more rigorous review of future taxonomic papers is recommended.

Existen pocos estudios sobre el desarrollo de la biología molecular en América Latina. El propósito de este trabajo es presentar una narrativa histórica de la expansión de la biología molecular en aquellos países donde ha tenido un mayor desarrollo: Argentina, Brasil, Cuba y México. En estos países, la biología molecular inicialmente derivó de áreas como la bioquímica y la fisiología celular, aunque más tarde, con el advenimiento de la genética molecular y la ingeniería genética, se consolidó como una disciplina por sí misma. Los principales campos de investigación en biología molecular en América Latina han sido los siguientes: genética microbiana, biología molecular de la célula, vacunas recombinantes, ingeniería genética de plantas, manipulación molecular de vías metabólicas, generación de anticuerpos modificados contra venenos de serpientes y alacranes (faboterápicos) y en la última década, el establecimiento de proyectos de secuenciación de genomas de bacterias, plantas y parásitos.

Two untapered, heterocytous species were observed and collected from the intertidal and supratidal zones of the Mexican coastline of the Pacific Ocean near Oaxaca and from the Gulf of Mexico. These populations were highly similar in morphology to the freshwater taxon Petalonema incrustans in the Scytonemataceae. However, 16S rRNA sequence data and phylogenetic analysis indicated that they were sister taxa to the epiphyllic, Brazilian species Phyllonema aveceniicola in the Rivulariaceae, described from culture material. While genetic identity between the two new species was high, they differed significantly in morphology, 16S rRNA gene sequence identity, and sequence and structure of the 16S-23S ITS region. Their morphology differed markedly from the generitype of the previously monotypic Phyllonema, which has tapered, heteropolar, single-false branched trichomes with very thin or absent sheath. The two new species, Phyllonema ansata and Phyllonema tangolundensis, described from both culture and environmental material, have untapered, isopolar, geminately false branched trichomes with thick, lamellated sheaths, differences so significant that the species would not be placed in Phyllonema without molecular corroboration. The morphological differences are so significant that a formal emendation of the genus is required. These taxa provide a challenge to algal taxonomy because the morphological differences are such that one would logically conclude that they represent different genera, but the phylogenetic evidence for including them all in the same genus is conclusive. This conclusion is counter to the current trend in algal taxonomy in which taxa with minor morphological differences have been repeatedly placed in separate genera based primarily upon DNA sequence evidence.

New approaches in taxonomy and the introduction of molecular tools have substantially changed the taxonomy of cyanobacteria, leading to new genera and species being defined based on genetic and morphological investigations. In addition, molecular tools have confirmed several previously defined cyanobacteria genera, including some based on morphological and ecological features. Several of them have also been split into new generic entities, such as Brasilonema. In the central region of Mexico, several populations have been identified to share some traits with this new genus. In the region of Tolantongo, Hidalgo (Hgo), we found cyanobacteria populations that correspond to Brasilonema description (Fiore et al. 2007), however the development of trichomes and hormogonia did not agree with the diagnosis of Brasilonema. We describe and analyze the cyanobacteria populations that we found in Tolantongo, and compare their features with the diagnostic generic features and those of several Brasilonema species. The results of morphological analyses were tested using molecular phylogenetic data derived from 16S RNA gene sequencing and the use of marker cpcBA-IGS for phycocyanin operon. From our analyses we conclude that the strain from Tolantongo belongs to the genus Brasilonema, and the differences observed are sufficient to propose a new species.

We used the wing somatic assay in Drosophila melanogaster to test the hypothesis that two phytoextracts from Cecropia obtusifolia Bertol (Cecropiaceae) and Equisetum myriochaetum Schlecht. et Cham (Equisetaceae), which are used in folk medicine to treat type 2 diabetes mellitus, could detoxify the mutagen hydrogen peroxide.Third instar larvae from standard (ST) and high-bioactivation (HB) crosses were chronically exposed to different concentrations of the phytoextracts. Hydrogen peroxide was used to induce oxidative stress and was chronically tested in both crosses. Catalase activity was measured in larvae of both strains 48 h after treatment with hydrogen peroxide. A pretreatment protocol was devised to test the antimutagenic potency of the medicinal extracts.The present study showed that neither of the phytoextracts were genotoxic in Drosophila. Interestingly, the antioxidant enzyme activity levels were different between the larvae. Hydrogen peroxide resulted in a significant genotoxic effect in the ST cross, whereas a detoxification of hydrogen peroxide was found in the HB cross. Thus, catalase was stimulated in the HB cross, which was indicative of a cellular defense mechanism mounted against a xenobiotic hazard. We found that the percentage of inhibition of spots produced by E. myriochaetum was much higher than that induced by Cecropia obtusifolia.These results are in agreement with the uses of these phytoextracts in traditional medicine. Indeed, the lack of genotoxicity and the antimutagenic activity observed for both phytoextracts validates their use as a therapeutic modality to treat diabetic patients. Moreover, these extracts are suitable for consumption as teas and/or phytomedicines.

This paper is a contribution to the morphological and molecular characterization of the cyanobacterium Brasilonema roberti-lamii from populations found in Central Mexico. The general growth form and the morphological, morphometric and ecological characteristics of the populations studied clearly correspond to those described for Brasilonema roberti-lamii (basionym: Tolypothrix roberti-lamii ) from the French Antilles. Based on molecular data from DNA sequencing of the16S rRNA gene and the IGS of the cpc B- cpc A phycocyanin operon ( cpc BA-IGS), we propose that the populations that we studied are closely related to those of other Brasilonema species, including B. octagenarum UFV-OR1, UFV-E1 and HA4187-MV1-p1F, Brasilonema sennae CENA 114, B . tolantongensis , B . terrestre CENA 116, B . angustatum HA4187-MV1-B2+p1F and HA4187-MV1-B2+p1H and B . bromeliae SPC951. Our findings support the transference of Tolypothrix roberti-lamii , which was made based exclusively on morphological criteria, to Brasilonema . The use of molecular analyses in addition to traditional morphological and ecological criteria, known as polyphasic approach, is a good alternative to describe taxa of cyanobacteria, mainly at the genus and species levels.

Debaryomyces hansenii is a spoilage yeast able to grow in a variety of ecological niches, from seawater to dairy products. Results presented in this article show that (i) D. hansenii has an inherent resistance to H2O2 which could be attributed to the fact that this yeast has a basal catalase activity which is several-fold higher than that observed in Saccharomyces cerevisiae under the same culture conditions, (ii) D. hansenii has two genes (DhCTA1 and DhCTT1) encoding two catalase isozymes with a differential enzymatic activity profile which is not strictly correlated with a differential expression profile of the encoding genes.