Javier Carmona Jiménez

Two new antibacterial norabietane diterpenoids from cyanobacteria, Microcoleous lacustris

Two abietane diterpenes were isolated from cyanobacteria Microcoleous lacustris, 20-nor-3α-acetoxyabieta-5,7,9,11,13-pentaene and 20-nor-3α-acetoxy-12-hydroxy-abieta-5,7,9,11,13-pentaene. These compounds were assayed against Staphylococcus aureus, Staphylococcus epidermidis, Salmonella typhi, Vibrio cholerae, Bacillus subtilis, Bacillus cereus, Escherichia coli, and Klebsiella pneumoniae. Both compounds showed activity against S. aureus, S. epidermidis, S. typhi, and V. cholerae, but not against the other bacteria.Two abietane diterpenes were isolated from cyanobacteria Microcoleous lacustris, 20-nor-3α-acetoxyabieta-5,7,9,11,13-pentaene and 20-nor-3α-acetoxy-12-hydroxy-abieta-5,7,9,11,13-pentaene. These compounds were assayed against Staphylococcus aureus, Staphylococcus epidermidis, Salmonella typhi, Vibrio cholerae, Bacillus subtilis, Bacillus cereus, Escherichia coli, and Klebsiella pneumoniae. Both compounds showed activity against S. aureus, S. epidermidis, S. typhi, and V. cholerae, but not against the other bacteria.

Occurrence of free-living amoebae in streams of the Mexico Basin.

Free-living amoebae (FLA) are protozoa that are widely distributed in nature. They are important in the cycling of nutrients in aquatic food chains, but their distribution in natural aquatic environments is not well known. We conducted a survey to determine the presence and distribution of FLA and their relation to some physicochemical parameters in streams of the Mexico Basin in Central Mexico. Thirty-two sites from 18 streams were sampled. Samples were centrifuged and cultured onto NNA-media to isolate amoebae. Identifications were based on morphology. The pathogenicity of Acanthamoeba isolates was tested. Oxygen saturation, temperature, pH, specific conductance, water flow, dissolved reactive phosphorus, nitrites, nitrates, ammonia, dissolved inorganic nitrogen and coliforms were determined. One hundred-and-twenty FLA representing 18 genera were identified. The most frequent genera were Vannella, Rosculus and Acanthamoeba. The frequency of potentially pathogenic FLA was low and only 3 Acanthamoeba isolates were invasive in mice. The highest species richness of FLA was found in streams located into agriculture activity areas and those close to small villages that discharge wastewater into them. Water temperatures were always below 17°C. Oxygen saturation and pH were within the limits for the growth of most FLA. The presence of Acanthamoeba and Naegleria was low; nevertheless, they include potentially pathogenic species and can act as vectors and reservoirs for microbial pathogens and can produce human infections.

Somatic meiosis and development of the juvenile gametophyte in members of the Batrachospermales sensu lato (Rhodophyta)

Abstract Seven populations (six in culture and one sampled directly from nature) of the freshwater red algal families Batrachospermaceae, Lemaneaceae and Thoreaceae were examined, involving three species of Batrachospermum, two of Paralemanea and one of Thorea. All ‘Chantransia’ stages ultimately produced juvenile gametophytes. The production of juvenile gametophytes in the three populations of Batrachospermum was generally most abundant at 15°C and low irradiances (47−68 μmol photons m−2 s−1). The most abundant gametophyte development in the Paralemanea species was observed at 10°C and low or high irradiances (47−142 μmol photons m−2 s−1). Gametophyte production in Thoreaceae occurred at higher temperatures (20°C) and also at low irradiances. In species of the Batrachospermaceae and Lemaneaceae, the ‘elimination cells’ can be situated on the basal or suprabasal cell of the juvenile gametophyte, but the position is usually fixed in individual species. The presence and position of the elimination cells remain to be established in Thoreaceae. Our results corroborate a previous study suggesting that the position of elimination cells is such a constant feature that it is of potential diagnostic value at the generic or infrageneric (sectional or specific) level. The characteristics observed in the development of the juvenile gametophytes in species of Batrachospermaceae and Lemaneaceae essentially agreed with general descriptions in the previous studies. The characteristics of the Thoreaceae, with a distinctive developmental pattern of the juvenile gametophyte and the occurrence of two morphological types in the ‘Chantransia’ stage, support the proposal to elevate it to the ordinal level. Two remarkable observations in Batrachospermum species were the production of numerous juvenile gametophytes from filaments of the same plant of the ‘Chantransia’ stage and the formation of a system of rhizoidal filaments or cell agglomeration of the juvenile gametophytes, which produced new gametophytes. These two characteristics potentially increase the formation of additional gametophytes under favourable conditions.

Microhabitat and morphometric variation in two species of Prasiola (Prasiolales, Chlorophyta) from streams in central Mexico

Prasiolales are characterized by high morphological plasticity. This problem in taxonomic delimitation of the species may be a result of environment heterogeneity. Habitat characteristics and morphological variation of P. mexicana and P. nevadensis, two species of freshwater leaf-like thallus green algae, were investigated in five sites in central México where the morphological traits of these species overlap. Comparisons were made between habitat characteristics among streams and transects with and without Prasiola samples. Although no consistent correlation was found between environmental variables and morphological traits, a significantly wider range of habitat characteristics of current velocity and irradiance and morphometric variation (lamina length, lamina diameter, cell length, surface of the thallus, thickness and number of layers) suggested that P. mexicana was more plastic than P. nevadensis in its physicochemical requirements. Our results suggest that small variation of microhabitat conditions in P. nevadensis (irradiance and current velocity) could explain its very restricted geographic range in streams in central Mexico.

Taxonomy and distribution of Paralemanea (Lemaneaceae, Rhodophyta) in Central Mexico

Departamento de Zoologia e Botanica Universidade Estadual Paulista, Rua Cristovao Colombo, Sao Jose do Rio Preto, SP

A new species and expanded distributions of freshwater Audouinella (Acrochaetiaceae, Rhodophyta) from Central Mexico and south-eastern Brazil

Eighteen collections of red-coloured Audouinella from Central Mexico and southeastern Brazil detected three species. The most common species, A. eugenea, is characterized by macroscopic thalli, the erect system consisting of filaments with cylindrical cells, undifferentiated into proximal and distal parts, and relatively large monosporangia (≥12.0 µm long). Spermatangia and possible propagules were observed in some Mexican populations. This is the third Audouinella species observed to have gametangia and the first member of the Acrochaetiales with putative propagules. The second species, from Central Mexico, was characterized by the following features : macroscopic thalli, the erect system differentiated into proximal parts with cylindrical cells, unbranched or rarely branched, and distal parts with barrel-shaped cells, abundantly branched to form dense fascicles, with alternate or dichotomous branching, some at right-angles to the axis, and relatively large monosporangia (≥12.0 µm long). The morphologically distinct proximal and distal portions of the erect system, the latter forming dense fascicles, was a consistent character so far unknown in Audouinella; thus, we propose a new species, A. huastecana sp. nov. The third species is a microscopic epiphyte, A. meiospora, with a well-developed prostrate system composed of creeping and loosely aggregated filaments, and a short homogeneous erect system (≤15 cells) of filaments with cylindrical or barrel-shaped cells and small monosporangia (≤13.0 µm long). A. eugenea and A. meiospora are characterized for the first time from the Southern and Northern Hemispheres, respectively, both occurring mostly in areas of tropical or subtropical rainforests. A. meiospora is reported from new macroalgal hosts. A. eugenea and A. huastecana tended to occur in warm, alkaline waters with a high ion content that were moderate to fast flowing, whereas A. meiospora was not associated with particular habitats.

ESTUDIO DEL VALOR INDICADOR DE LAS COMUNIDADES DE ALGAS BENTÓNICAS: UNA PROPUESTA DE EVALUACIÓN Y APLICACIÓN EN EL RÍO MAGDALENA, CIUDAD DE MÉXICO

The application and development of environmental laws governing watershed management requires identification of biological indicators, parameters and measures to establish its ecological status, for which the present study aims to characterize the ecological indicator value of stream benthic algae in an urban area of Mexico City. Six sites of the Magdalena river were studied in the most contrasting seasons: dry-warm, rainy and dry-cold. At each site the physicochemical parameters of water were recorded and 10 samples were collected: Five with visible algal growths and five with diatoms. The environmental quality of each site was determined by the trophic status and its confirmation with the richness and benthic algal diversity, through a canonical correspondence analysis and the calculation of the indicator value of species (IndVal). According to the trophic status, three groups of sites were recognized. The first group (G1) was assessed as reference of the oligotrophic conditions and presented 11 species with the highest IndVal, protruding: Encyonema silesiacum, Gomphonema parvulum, Navicula cryptocephala, Planothidium lanceolatum, Vaucheria bursata, Placoma regulare and Nostoc parmelioides. A second group (G2) was associated with 15 species considered detectors, which were tolerant to increased nutrients in at least one season, such as Diatoma mesodon and Prasiola mexicana. The third group (G3) included sites with species that had a wide range of tolerance to pollution: Fistulifera saprophila , Nitzschia minuta , Nitzschia palea , Nitzschia recta and Phormidium autumnale. The species IndVal of Magdalena River has established reference sites of good environmental quality and those that are altered by human activities, therefore they are recommended as the first step in a methodological proposal for a long-term biomonitoring through a biological index.

Taxonomy and distribution of freshwater Blennothrix ganeshii Watanabe et Komárek (Oscillatoriaceae, Cyanophyceae) from central Mexico

The genus Blennothrix belongs to the family Oscillatoriaceae (subfamily Oscillatorioideae), differing from others in the subfamily by the presence of several trichomes in a sheath. Freshwater members of Blennothrix have been recently divided into eight species (Komarek 1998), with the taxon B. ganeshii Watanabe et Komarek reported from three sites in two tropical basins of the central region of Mexico. However, information on anatomical (vegetative and reproductive) characters and environmental distribution is scarce and species determination is uncertain. This study analyses the anatomical structure of Blennothrix populations distributed in different sites along the central tropical region of Mexico in order to determine the taxonomic status of the studied populations. Eight populations were sampled, with concurrent environmental data recorded. Morphological characters previously considered to be of taxonomic importance, as well as complementary features such as algal mat length, filament diameter, trichome width, length of cells, and thickness and shape of the sheath were measured in several filaments of each sample. Our results showed that all the observed populations in the central region of Mexico fit within the circumscription of B. ganeshii (Watanabe & Komarek 1989, Komarek 1998). However, two important morphological features were observed in all populations. First, branches were rarely present and varying in frequency from 1 to 3 trichomes per filament. Second, the presence of a transverse lamellation due to constriction in the longitudinal axis of the sheath was observed. Some morphological characters described for this species were extended.

The distribution of Rhodophyta in streams of Central Mexico

The distribution of species of Rhodophyta was investigated in 424 stream segments, sampled from 1981–1999 in three river basins from central Mexico. Red algae occurred in 12% of the stream segments sampled, a low frequency compared to major surveys in other parts of the world (18–65%). Sixteen species of freshwater red algae were found, of which the most widespread were Compsopogon coeruleus (24 sites) and Hildenbrandia angolensis (16 sites). Two groups of species were clearly distinguished on the basis of environmental characteristics. The first group, which included Batrachospermum gelatinosum, Paralemanea annulata, P. mexicana and Sirodotia suecica, is found in temperate climates, high altitudes (>1700 m), and cold or temperate waters (12–18°C) that are slightly acidic (pH 5.5–6.5) and of low specific conductivity (77–86 μS . cm–1). The second group, including Chroodactylon ornatum, Compsopogon coeruleus, Hildenbrandia angolensis, Audouinella eugenea, A. huastecana, A. meiospora, Batrachospermum globosporum, Sirodotia huillensis and Thorea hispida, is of subtropical to tropical climates, low altitudes ( 21°C) that are neutral to slightly alkaline (pH 7.0–8.6) and of high specific conductivity (160–1990 μS.cm–1). Half of the species found in this study were exclusively of calcareous sites from within a highly homogeneous limestone region (56% Ca). The rest of the sites with rhodophytes were found in sub-basins with andesitic-basaltic or calcareous substrates, and in temperate to semidesertic climates that provoke dramatic changes in the water level of the river or even the complete absence of permanent rivers. A high percentage of the currents contained an influx of organic material in which populations of Compsopogon coeruleus, described as tolerant of these conditions, could be found. The sub-basins that were most similar and had the least diversity corresponded to high mountain regions of Central Mexico (HP and HB). The overall species composition for streams and rivers of Central Mexico revealed high similarities with other tropical regions and had few species in common with freshwater red algal floras of other continents.

Phenology of Paralemanea mexicana (Batrachospermales, Rhodophyta) in a high‐altitude stream in central Mexico

The morphology and phenology of Paralemanea mexicana (Kützing) Vis et Sheath was evaluated seasonally in a fifth order high‐altitude stream in central Mexico. The gametophytes grew during oligotrophic and eutrophic conditions, and during particular microhabitat conditions: high current velocity (40–240 cm s−1), low to medium irradiance (5–973 μmol photons m−2 s−1), and shallow depth (1–30 cm). The abundance of gametophytes was positively correlated with low temperature, high current velocity and concentrations of soluble reactive phosphorus. Interestingly, monoecious gametophytes formed two types of branches, true branches with sympodial pattern originating from meristematic cells in variable number, and abundant false branches produced during the development of the ‘Chantransia’ stage in the surface of the gametophyte or by uniseriate filaments arising within the thallus lumen. These filaments generally produce gametophytes and suggest that they could support the germination of carpospores. The frequently whorled branches are the result of a false branching pattern and are exclusive to P. mexicana. These morphological and reproductive characteristics appear to be biomechanical adaptations to avoid detachment and increase reproductive success. Efficient reproductive strategies of P. mexicana observed in this study can be interpreted as adaptations to successfully colonize streams; however, these features may not have been common in the study region due to restricted microhabitat conditions and geographic isolation.