Panorama florístico actual de las algas continentales mexicanas

Background. In 2011, we published an overview of Mexican freshwater algae. Objectives. Eleven years later, we make an evaluation of the advances in each one of the subjects related to the knowledge of the continental algal groups: number of species registered in the country and in each state of the republic, types of publications with floristic information, distribution of the taxa in the states and a list of the new species described in the period. Methods. The bibliographic and floristic information databases available online (bdLACET, AlgaeBase) were analyzed. Results. The most reliable number of records of valid taxa, no synonims, in Mexico is 4,268. Several states increased their floristic list by more than 50%. Conclusions. We discuss the importance of continuing with floristic work and the elements that comprise it, the role played by the current policies of scientific journals regarding inventory work, and the importance of having reliable regional databases.Antecedentes. En 2011 publicamos un panorama de las algas dulceacuícolas mexicanas en esta revista. Objetivos. Once años después, hacemos una evaluación de los avances en cada uno de los temas relacionados con el conocimiento de los grupos algales continentales: número de especies registradas en el país y en cada estado de la república, tipos de publicaciones con información florística, distribución de los taxones en los estados y un listado de las especies nuevas descritas en el periodo. Métodos. Se analizaron las bases de datos bibliográficas y de información florística disponibles en línea (bdLACET, AlgaeBase). Resultados. El número más confiable de registro de taxones válidos, no sinónimos en México es de 4268. Varios estados aumentaron su elenco florístico en más del 50%. Conclusiones. Discutimos la importancia de continuar con el trabajo florístico y los elementos que lo conforman, el papel que juegan las políticas actuales de las revistas científicas respecto al trabajo inventarial y la importancia de contar con bases de datos regionales confiables

Un panorama gráfico de las algas de agua dulce de México

The actual knowledge about the freshwater algae of Mexico is very uneven from various points of view, despite its recognized potential as indicators of environmental conditions and to be the basal part of trophic chains in aquatic environments. The largest number of records of algae is in the central area of the country, with five states comprising more than 56% of total number of records. The Bacillariophyta are the group with the highest number of records, both nationally and by number of states. To this inequality, must be added that there is generally a poor level of documentation of species. There are records with the species name only and whose description or illustration has not been possible to locate, even with the recent documentary search resources. The graphical review presented highlights the degree of knowledge we have of the algae by states, taxonomical groups and the most studied environments; the discussion is supported with some analysis of the causes that affect the poor knowledge of freshwater algae in Mexico.El conocimiento actual sobre las algas dulceacuícolas de México es muy desigual desde varios puntos de vista, a pesar de su reconocido potencial como indicadores de condiciones ambientales y de constituir la parte basal de las cadenas tróficas en los ambientes acuáticos. La mayor cantidad de registros de algas procede de la zona central del país, con cinco estados que reúnen más del 56% del total de los mismos. Las Bacillariophyta son el grupo con mayor número de registros, tanto a nivel estatal como nacional. A esta desigualdad hay que agregar que el grado de documentación que se tiene de las especies en general es deficiente. Existen registros de especies de los que sólo se conoce el nombre y cuya descripción o ilustración no ha sido posible ubicar, ni con los recursos de búsqueda documental recientes. El panorama gráfico que aquí presentamos resalta el grado de conocimiento que se tiene de las algas por estados, por grupos y por ambientes más estudiados; la discusión se sustenta con algunos análisis de las causas que influyen en el conocimiento deficiente de las algas dulceacuícolas de México

Timescale lessons of <em>Durinskia baltica</em> (Kryptoperidiniaceae, Dinophyta) from freshwater through a molecular phylogeny

Background: The evolutionary pattern of dinophytes is complex and requires comprehensive taxonomic studies addressing the species' development and morphology, ecology, evolution, and genetics. Questions: How recent was the transition of D. baltica from Mexico to freshwater based on a calibrated phylogeny tree of the Kryptoperidiniaceae? Studied species and data description: Durinskia baltica, Kryptoperidiniaceae and the known fossil record of dinotoms (endosymbiont diatom-host dinophytes). Study sites and dates: Xochimilco, Mexico City.  2010 to 2019. Methods: Phylogenies were constructed with Bayesian inferences and host sequences were calibrated with a relaxed clock method. Results: We obtained genetic sequences of the 18S rDNA sector in the host and the rbcL sector in the endosymbiont. The Nitzschia-type endosymbiont is genetically distinct from endosymbionts of other dinotomes with the same diatom type. In contrast, considering the known freshwater species of Durinskia, the genetic relationship between hosts is robust and of recent origin. The antiquity of the Mexican sequence coincides with the geological origin of the Xochimilco basin, suggesting particularities in the evolutionary history of dinotomes linked to the geographic regions they inhabit. Conclusions: Our evolutionary scenario with a calibrated phylogeny indicates that the transition of Durinskia baltica to freshwater in the Xochimilco basin is geologically contextualized. The historical environmental change of Lake Xochimilco with respect to salinity corresponds with an initial colonization of D. baltica in a brackish environment and its subsequent adaptation to freshwater

Ecología de cianoprocariontes epífitas que habitan ambientes lóticos de la Cantera Oriente, Ciudad de México

La Cantera Oriente alberga un componente de microalgas diverso. Los ecosistemas lénticos han recibido mucha más atención que los sistemas lóticos, lo que hace importante su estudio. Objetivos. Comparar comunidades de cianoprocariontes de un ambiente lótico natural y otro artificial, midiendo la densidad y frecuencia relativas de las especies y su asociación con factores ambientales. Métodos. Se muestrearon mensualmente las clorofitas filamentosas y la madera y raíces de plantas sumergidas en dos ambientes lóticos (uno natural y otro artificial) de septiembre de 2012 a septiembre de 2013, para estudiar las cianoprocariontes epífitas presentes en ellos. Simultáneamente, se obtuvieron datos fisicoquímicos con mediciones de campo y análisis de laboratorio. Las especies se evaluaron de acuerdo con el Índice de Valor de Importancia (IVI). Resultados. Sólo el 31 % de las cianoprocariontes fue compartido por ambos sitios.Los datos fisicoquímicos mostraron igualdad de varianzas y no se correlacionaron con los valores del IVI, denotando un bajo nivel de disturbio ambiental. La comparación estadística proporcional del IVI observado y teórico de las especies de cada ambiente (prueba Chi cuadrada), estableció que las cianoprocariontes se asociaron con el tipo deambiente, el tipo de sustrato y la estación climática. Conclusiones. Los ambientes lóticos de la Cantera Oriente se caracterizan por un bajo nivel de disturbio, que no afecta la presencia ni la biomasa de las cianoprocariontes. El IVI se asocia con el tipo de ambiente y de sustrato como sitio de colonización y parece explicar las preferencias de hábitat para algunas especies

A Novel Microbialite-Associated Phototrophic Chloroflexi Lineage Exhibiting a Quasi-Clonal Pattern along Depth

Chloroflexales (Chloroflexi) are typical members of the anoxygenic photosynthesizing component of microbial mats and have mostly been characterized from communities associated to hot springs. Here, we report the assembly of five metagenome-assembled genomes (MAGs) of a novel lineage of Chloroflexales found in mesophilic lithifying microbial mats (microbialites) in Lake Alchichica (Mexico). Genomic and phylogenetic analyses revealed that the bins shared 92% of their genes, and these genes were nearly identical despite being assembled from samples collected along a depth gradient (1-15m depth). We tentatively name this lineage Candidatus Lithoflexus mexicanus. Metabolic predictions based on the MAGs suggest that these chlorosome-lacking mixotrophs share features in central carbon metabolism, electron transport, and adaptations to life under oxic and anoxic conditions, with members of two related lineages, Chloroflexineae and Roseiflexineae. Contrasting with the other diverse microbialite community members, which display much lower genomic conservation along the depth gradient, Ca. L. mexicanus MAGs exhibit remarkable similarity. This might reflect a particular flexibility to acclimate to varying light conditions with depth or the capacity to occupy a very specific spatial ecological niche in microbialites from different depths. Alternatively, Ca. L. mexicanus may also have the ability to modulate its gene expression as a function of the local environmental conditions during diel cycles in microbialites along the depth gradient

Variación morfológica de algunas especies de Ophiocytium Nägeli (Xantophyceae) de cuerpos de agua temporales del Estado de México

The species belonging to genus Ophiocytium Nägeli (Mischococcales, Xanthophyceae) have a world distribution in acidic to neutral environments; these species are little common in floristic records in our country. The suitable conditions observed in Santa Ana, in México State, for development of Ophiocytium species made possible their study for several months (December 1993 April 1995). Nine morphotypes were characterized. Although they may correspond to species according to bibliography, only five were determined after evaluation of morphological characters that are used in the specific delimitation. Additionally, the variation of O. parvulum, the most abundant species, was used to propose an annual development pattern that may be extrapolated to all species in Santa Ana.Las especies del género Ophiocytium Nägeli (Mischococcales, Xanthophyceae) tienen una distribución mundial principalmente en ambientes ácidos a neutros. Son especies poco comunes en los registros florísticos de nuestro país, pero en la localidad de Santa Ana, en el Estado de México, se presentaron condiciones adecuadas para su desarrollo, por lo que fue posible observarlas durante un tiempo prolongado (diciembre 1993 abril 1995). Se caracterizaron 9 variantes morfológicas que, aunque corresponden con especies según la bibliografía, fueron ubicadas sólo en cinco una vez que se evaluaron los caracteres morfológicos que se utilizan en la delimitación específica. Además la variación morfológica de O. parvulum, la especie más abundante, se utilizó para proponer un patrón de desarrollo durante el ciclo anual que podría extrapolarse al conjunto de especies en Santa Ana

Metagenome-based diversity analyses suggest a significant contribution of non-cyanobacterial lineages to carbonate precipitation in modern microbialites

Frontiers in Microbiology 6 (2015): 797 This Document is Protected by copyright and was first published by Frontiers. All rights reserved. It is reproduced with permissionCyanobacteria are thought to play a key role in carbonate formation due to their metabolic activity, but other organisms carrying out oxygenic photosynthesis (photosynthetic eukaryotes) or other metabolisms (e.g., anoxygenic photosynthesis, sulfate reduction), may also contribute to carbonate formation. To obtain more quantitative information than that provided by more classical PCR-dependent methods, we studied the microbial diversity of microbialites from the Alchichica crater lake (Mexico) by mining for 16S/18S rRNA genes in metagenomes obtained by direct sequencing of environmental DNA. We studied samples collected at the Western (AL-W) and Northern (AL-N) shores of the lake and, at the latter site, along a depth gradient (1, 5, 10, and 15 m depth). The associated microbial communities were mainly composed of bacteria, most of which seemed heterotrophic, whereas archaea were negligible. Eukaryotes composed a relatively minor fraction dominated by photosynthetic lineages, diatoms in AL-W, influenced by Si-rich seepage waters, and green algae in AL-N samples. Members of the Gammaproteobacteria and Alphaproteobacteria classes of Proteobacteria, Cyanobacteria, and Bacteroidetes were the most abundant bacterial taxa, followed by Planctomycetes, Deltaproteobacteria (Proteobacteria), Verrucomicrobia, Actinobacteria, Firmicutes, and Chloroflexi. Community composition varied among sites and with depth. Although cyanobacteria were the most important bacterial group contributing to the carbonate precipitation potential, photosynthetic eukaryotes, anoxygenic photosynthesizers and sulfate reducers were also very abundant. Cyanobacteria affiliated to Pleurocapsales largely increased with depth. Scanning electron microscopy (SEM) observations showed considerable areas of aragonite-encrusted Pleurocapsa-like cyanobacteria at microscale. Multivariate statistical analyses showed a strong positive correlation of Pleurocapsales and Chroococcales with aragonite formation at macroscale, and suggest a potential causal link. Despite the previous identification of intracellularly calcifying cyanobacteria in Alchichica microbialites, most carbonate precipitation seems extracellular in this systemWe are grateful to Eleonor Cortés for help and good company during the field trip and to Eberto Novelo for helpful discussions at the UNAM lab. This research was funded by the European Research Council Grants ProtistWorld (PI PL-G., Grant Agreement no. 322669) and CALCYAN (PI KB, Grant Agreement no. 307110) under the European Union’s Seventh Framework Program and the RTP Génomique environnementale of the CNRS (project MetaStrom, PI DM

Prokaryotic and Eukaryotic Community Structure in Field and Cultured Microbialites from the Alkaline Lake Alchichica (Mexico)

The geomicrobiology of crater lake microbialites remains largely unknown despite their evolutionary interest due to their resemblance to some Archaean analogs in the dominance of in situ carbonate precipitation over accretion. Here, we studied the diversity of archaea, bacteria and protists in microbialites of the alkaline Lake Alchichica from both field samples collected along a depth gradient (0–14 m depth) and long-term-maintained laboratory aquaria. Using small subunit (SSU) rRNA gene libraries and fingerprinting methods, we detected a wide diversity of bacteria and protists contrasting with a minor fraction of archaea. Oxygenic photosynthesizers were dominated by cyanobacteria, green algae and diatoms. Cyanobacterial diversity varied with depth, Oscillatoriales dominating shallow and intermediate microbialites and Pleurocapsales the deepest samples. The early-branching Gloeobacterales represented significant proportions in aquaria microbialites. Anoxygenic photosynthesizers were also diverse, comprising members of Alphaproteobacteria and Chloroflexi. Although photosynthetic microorganisms dominated in biomass, heterotrophic lineages were more diverse. We detected members of up to 21 bacterial phyla or candidate divisions, including lineages possibly involved in microbialite formation, such as sulfate-reducing Deltaproteobacteria but also Firmicutes and very diverse taxa likely able to degrade complex polymeric substances, such as Planctomycetales, Bacteroidetes and Verrucomicrobia. Heterotrophic eukaryotes were dominated by Fungi (including members of the basal Rozellida or Cryptomycota), Choanoflagellida, Nucleariida, Amoebozoa, Alveolata and Stramenopiles. The diversity and relative abundance of many eukaryotic lineages suggest an unforeseen role for protists in microbialite ecology. Many lineages from lake microbialites were successfully maintained in aquaria. Interestingly, the diversity detected in aquarium microbialites was higher than in field samples, possibly due to more stable and favorable laboratory conditions. The maintenance of highly diverse natural microbialites in laboratory aquaria holds promise to study the role of different metabolisms in the formation of these structures under controlled conditions

Multifaceted approach for the analysis of the phototrophic microbial community in a freshwater recreational area of Xochimilco, México

16 pages, 6 figures, 3 tablesThe freshwater microbial community in a recreational area of Xochimilco, México was investigated and compared based on spatial (three different sites) and temporal (dry and rainy seasons) environmental variables. Many of the 16S- and 18S rRNA gene sequences recovered by DGGE fingerprinting analysis were related to phototrophic microbial phylotypes of known identity. Our genetic and morphological analysis indicated the ubiquitous presence of the microeukaryotic green algae Desmodesmus- Scenedesmus spp. and of the unicellular cyanobacteria Cyanobium spp. as the most representative populations in the samples. While 18S rRNA-DGGE fingerprinting analysis revealed a homogeneous community composition across sites and seasons, the 16S rRNA showed significant differences between localities and seasons. None of the cyanobacteria species with potential to produce toxins were identified across the investigated samples. Correlations between biotic and abiotic variables evidenced an important difference between the dry and the rainy season, with a greater consistency in data from the rainy season. According to Principal Component Analysis (PCA), a strong relation between inorganic nitrogen, species richness, and subaquatic irradiance determines environmental variability in Xochimilco. Complementary and relevant data in results obtained from microscopy, fingerprinting, and statistical analysis applied in ecology indicate that a multifaceted approach to the study of microbial communities is necessary to accomplish a comprehensive scientific framework and to generate proper management strategies. © Springer Science+Business Media B.V. 2009Authors thank grants to this project from CONACYT-S52720-Q and from DGAPA-UNAMPeer Reviewe