Genetic and morphological characterization of a new genotype of nervous necrosis virus circulating among Nile tilapia in the south of Egypt

Nervous necrosis virus (NNV) is the causative agent of viral nervous necrosis in freshwater and marine fishes. In this study, NNV circulating among wild and farmed Nile tilapia (Oreochromis niloticus) was genetically and morphologically characterized using reverse transcription polymerase chain reaction (RT-PCR), sequencing analysis, and transmission electron microscopy (TEM). Brain, eye, and other organ (spleen, kidney, heart, and liver) specimens were collected from 87 wild (66) and farmed (21) Nile tilapia fish during their adult or juvenile stage at different localities in Qena and Sohag governorates in southern Egypt. Among them, 57/87 fish showed suspected NNV clinical signs, and 30/87 were healthy. The results revealed that NNV was detected in 66 out of 87 fish (58.62% in the wild and 17.24% in farmed Nile tilapia by RT-PCR), and the prevalence was higher among diseased (55.17%) than in healthy (20.69%) fish. NNV was detected in the brain, eye, and other organs. Using TEM, virion size variations based on the infected organs were observed. Nucleotide sequence similarity indicated that NNVs had a divergence of 75% from other fish nodaviruses sequenced in Egypt and worldwide. Phylogenetic analysis distinguished them from other NNV genotypes, revealing the emergence of a new NNV genotype in southern Egypt. In conclusion, NNV is circulating among diseased and healthy Nile tilapia, and a new NNV genotype has emerged in southern Egypt. (AU)

Diverse type I and type II methanotrophs cultivated from an Indian freshwater wetland habitat

Wetlands are the main natural sources of methane emissions, which make up a significant portion of greenhouse gas emissions. Such wetland patches serve as rich habitats for aerobic methanotrophs. Limited knowledge of methanotrophs from tropical wetlands widens the scope of study from these habitats. In the present study, a freshwater wetland in a tropical region in India was sampled and serially diluted to obtain methanotrophs in culture. This was followed by the isolation of methanotrophs on agarose-containing plates, incubated under methane: air atmosphere. Methanotrophs are difficult to cultivate, and very few cultures of methanotrophs are available from tropical wetlands. Our current study reports the cultivation of a diverse community of methanotrophs from six genera, namely, Methylomonas, Methylococcus, Methylomagnum, Methylocucumis (type I methanotrophs) along with Methylocystis, Methylosinus (type II methanotrophs). A high abundance of methanotrophs (106–1010 methanotrophs/g fresh weight) was observed in the samples. A Methylococcus strain could represent a putative novel species that was also isolated. Cultures of Methylomagnum and Methylocucumis, two newly described type I methanotrophs exclusively found in rice fields, were obtained. A large number of Methylomonas koyamae strains were cultured. Our study is pioneering in the documentation of culturable methanotrophs from a typical tropical wetland patch. The isolated methanotrophs can act as models for studying methanotroph-based methane mitigation from wetland habitats and can be used for various mitigation and valorization applications. (AU)

Characterization of new diesel-degrading bacteria isolated from freshwater sediments / Caracterización de nuevas bacterias degradadoras de diesel aisladas de sedimentos de agua dulce

As the result of diesel’s extensive production and use as fuel for transportation, pollution with such complex mixtures of hydrocarbons is a major concern worldwide. The present study’s focus was to investigate the presence of diesel-degrading bacteria in different Danube Delta freshwater sediments. Ten bacterial strains capable to grow in a minimal medium with diesel as the sole carbon source were isolated and characterized in this study. Based on the phenotypic and molecular characteristics, the ten strains belong to four genera and seven species, such as Pseudomonas (P. aeruginosa, P. nitroreducens, P. resinovorans, P. multiresinivorans), Acinetobacter (A. tandoii), Bacillus (B. marisflavi), and Stenotrophomonas (S. maltophilia). All these bacteria were excellent biosurfactant producers, and they were able to tolerate saturated hydrocarbons, like n-heptane, n-decane, n-pentadecane, and n-hexadecane. The ten strains possess at least one alkane hydroxylase gene in their genome, and they were also able to tolerate and degrade diesel. Higher biodegradation rates of diesel were acquired for the strains from the genera Pseudomonas, Acinetobacter, and Stenotrophomonas, compared with that obtained for the Bacillus strain. Due to their remarkable potential to degrade diesel and produce biosurfactants, the ten isolated bacteria are attractive candidates for bioremediation of diesel-polluted environments.(AU)

Hongos fitopatógenos en ambientes terrestres y acuáticos presentes en Latinoamérica / Phytopatogenic fungi in terrestrial and aquatic environments present in Latin America

El propósito de esta revisión bibliográfica es dar a conocer los diferentes hongos fitopatógenos presentes en estos dos tipos de ambientes, y los factores que intervienen en la presencia o ausencia de los mismos.Materiales y métodos: Para la construcción de este artículo se planteó una búsqueda bibliográfica en las bases de datos: Pubmed, Science direct, Google scholar, Scielo y NCBI en inglés y español, utilizando los siguientes descriptores: Hongos, Microorganismos acuáticos, y Hongos en suelo.Resultados: En esta revisión bibliografía, se encontró en gran parte de los ambientes acuáticos, la presencia de, Aspergillus sp., Fusarium sp., Mucor sp., Penicillium sp., Alternaria sp., Trichoderma sp., Blastomyces sp., Geotrichum sp., etc. Además, en los ambientes terrestres, se hallaron hongos del género, Rhizopus sp., Fusarium sp., Beauveria sp., Absidia sp., Mucor sp., Aspergillus sp., Penicillium sp., Paecilomyces sp., etc. Así mismo, se investigó sobre los factores que determinan la concentración y diversidad en ambientes acuáticos y terrestres, en todos los tipos de hongos. En los ambientes acuáticos los principales factores fueron temperatura, lluvia, velocidad del agua, estados de los nutrientes, impacto antropogénico y abundancia de materia en descomposición y en los ambientes terrestres, el pH, el impacto antropogénico y la presencia de sustancias contaminantes.Conclusión: En el caso de los hongos en agua dulce, el género Aspergillus s fue el más representativo, en cuanto al ambiente terrestre los géneros Fusarium sp., y Rhizopus sp., fueron los predominantes en la mayoría de los estudios citados en esta revisión. (AU)

Objective: The purpose of this literature review is to know the different phytopathogenic fungi present in these two types of environments, and the factors involved in their presence or absence.Materials and methods: For the construction of this article, a bibliographic search was carried out in the following databases: Pubmed, Science direct, Google scholar, Scielo and NCBI in English and Spanish, using the following descriptors: Fungi, Aquatic microorganisms, and Fungi in soil.Results: In this bibliographic review, the presence of Aspergillus sp, Fusarium sp, Mucor sp, Penicillium sp, Alternaria sp, Trichoderma sp, Blastomyces sp, Geotrichum sp, etc. was found in most of the aquatic environments. In addition, in terrestrial environments, fungi of the genus Rhizopus sp, Fusarium sp, Beauveria sp, Absidia sp, Mucor sp, Aspergillus sp, Penicillium sp, Paecilomyces sp, etc. were found. Likewise, we investigated the factors that determine the concentration and diversity in aquatic and terrestrial environments, in all types of fungi. In aquatic environments, these are: temperature, rainfall, water velocity, nutrient status, anthropogenic impact and abundance of decomposing matter. On the other hand, in terrestrial environments, we find: pH, anthropogenic impact, and the presence of pollutants. Conclusion: In the case of fungi in fresh water, the genus Aspergillus sp was the most representative, while in the terrestrial environment the genus Fusarium sp, and Rhizopus sp, were the most predominant with their appearance in most of the studies cited in this review. (AU)

Bioremediation potential and lead removal capacity of heavy metal-tolerant yeasts isolated from Dayet Oum Ghellaz Lake water (northwest of Algeria) / Potencial de biorremediación y capacidad de eliminación de plomo de levaduras tolerantes a metales pesados aisladas del agua del lago Dayet Oum Ghellaz (noroeste de Argelia)

Seven metal-resistant yeast strains were isolated and selected from Dayet Oum Ghellaz Lake water (northwest of Algeria) known as a highly polluted area by lead and cadmium. The yeast strains were screened on the basis of their resistance to seven heavy metals Hg, Cr, Cd, Pb, Cu, Zn, and Fe and characterized by molecular and phylogenetic analysis. The sequencing of the D1/D2 domain of the 26S rRNA genes revealed the affiliation of the seven yeast isolates to Rhodotorula mucilaginosa, Clavispora lusitaniae, and Wickerhamomyces anomalus species. All yeast strains were halotolerant as they were able to grow in 10–15% NaCl. The yeast isolates were highly resistant to the studied heavy metals and exhibited different tolerance according to the metal type. The highest minimum inhibitory concentrations (MIC) were observed in R. mucilaginosa RO7 and W. anomalus WO2 strains which were then selected for lead removal assays. The present study is the first to investigate the lead elimination by W. anomalus. The lead uptake was significantly affected by biomass concentration in a reverse relationship, with purification percentages estimated at 98.15 ± 0.9% and 97.046 ± 0.47% and removal efficiency of 12.68 ± 0.91 and 15.55 ± 0.72 mg/g for W. anomalus WO2 and R. mucilaginosa RO7, respectively. The investigated metal-tolerant yeast strains proved to be promising candidates for bioremediation processes of heavy metals. This work amends the metal-resistant yeast bank with new strains having interesting abilities to resist to relatively high concentrations of toxic heavy metals and which can be used in the near future as low-cost biosorbents.(AU)

Utilization of lactose and presence of the phospho-β-galactosidase (lacG) genein Lactococcus garvieae isolatesfrom different sources

This study evaluates the utilization of lactose (Lac) and the presence of the phospho-β-galactosidase (lacG) gene as markers for distinguishing between fish (Lac-/lacG-) and dairy isolates (Lac+/lacG+) of Lactococcus garvieae, using a panel of L. garvieae isolates from different sources. None of the fish isolates produced acid from lactose (Lac-), however Lac-/lacG- isolates were observed in pigs, cows, birds and humans. Most of the dairy isolates (77.8%) were Lac+/lacG+, but some dairy isolates did not produce acid from this sugar. Data in the present study show that the ability to metabolize lactose and the presence of the lacG gene are heterogeneously scattered among L. garvieae isolates of different sources. Therefore, the use of these criteria as markers to differentiate between L. garvieae isolates of dairy and fish origin should be considered with caution (AU)

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Cell aggregation: a mechanism of pathogenic Leptospira to survive in fresh water / Agregación celular: un mecanismo de especies patógenas de Leptospira para sobrevivir en agua dulce

IS200 is a mobile element found in a variety of eubacterial genera, such as Salmonella, Escherichia, Shigella, Vibrio, Enterococcus, Clostridium, Helicobacter, and Actinobacillus. In addition, IS200-like elements are found in archaea. IS200 elements are very small (707-711 bp) and contain a single gene. Cladograms constructed with IS200 DNA sequences suggest that IS200 has not spread among eubacteria by horizontal transfer; thus it may be an ancestral component of the bacterial genome. Self-restraint may have favored this evolutionary endurance; in fact, unlike typical mobile elements, IS200 transposes rarely. Tight repression of transposase synthesis is achieved by a combination of mechanisms: inefficient transcription, protection from impinging transcription by a transcriptional terminator, and repression of translation by a stem-loop mRNA structure. A consequence of IS200 self-restraint is that the number and distribution of IS200 elements remain fairly constant in natural populations of bacteria. This stability makes IS200 a suitable molecular marker for epidemiological and ecological studies, especially when the number of IS200 copies is high. In Salmonella enterica, IS200 fingerprinting is extensively used for strain discrimination (AU)

La supervivencia de Leptospira en ambientes húmedos, fuera del mamífero hospedador, facilita la transmisión de la enfermedad. Nosotros estudiamos la supervivencia de Leptospira interrogans serovar Canicola en medios acuosos carentes de nutrientes. En agua destilada (pH 7,2), las leptospiras conservaron la movilidad durante 110 días. Sin embargo, cuando se incubaron en un medio semisólido, compuesto de agua destilada y 0,5 por ciento de agarosa purificada, sobrevivieron 347 días. En este medio viscoso se observó que las leptospiras formaban agregados. Ni la presencia de nutrientes ni la de antibióticos (ampicilina o tetraciclina) inhibieron la agregación. El análisis por inmunotransferencia indica que en las leptospiras incubadas en agua disminuye la expresión de la proteína de membrana interna LipL31; no obstante, conservan la expresión de otras proteínas de membrana. Este estudio proporciona una visión de los mecanismos que permiten la supervivencia de las especies patógenas de Leptospira en ambientes acuáticos naturales, un proceso importante en el ciclo natural de la leptospirosis (AU)

Estudio de la influencia de los suelos contaminados por metales pesados en las aguas naturales / Influence of polluted soils by heavy metals on natural water

En este trabajo se estudia las características de los lixiviados procedentes de suelos carbonatados, que han sido sometidos a un proceso de desplazamiento usando un sistema experimental de columnas. Las características químicas de la solución efluente ponen de manifiesto que, la mineralización de las muestras se debe, principalmente, a la disolución de minerales carbonatados. No obstante, es de resaltar la contribución que tiene los procesos de hidrólisis de minerales silicatados.Identificada la solución, se procedió a los ensayos de contaminación utilizando una mezcla de metales pesados, todos ellos con igual concentración, observándose que los porcentajes de absorción fueron superiores al 90 por ciento, siendo el Cr y el Cu los cationes más retenidos y el Cd el catión más móvil. A continuación se sometieron los suelos a cuatro procesos de lavado sucesivos, apreciándose una secuencia de retención en suelo de: Cr>Cu>Pb"Zn"Ni>Cd. Esta secuencia permite reconocer que Cr, Cu y Pb son los cationes de metales pesados más fuertemente adsorbidos en situación de competencia, y es el Cd el catión que presenta mayor índice de peligrosidad, tanto por su naturaleza tóxica como por su movilidad (AU)

Floraciones tóxicas de cianobacterias detectadas en el suroeste de la península ibérica

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Cyanobacterial diversity in extreme environments in Baja California, Mexico: a polyphasic study

Cyanobacterial diversity from two geographical areas of Baja California Sur, Mexico, were studied: Bahia Concepcion, and Ensenada de Aripez. The sites included hypersaline ecosystems, sea bottom, hydrothermal springs, and a shrimp farm. In this report we describe four new morphotypes, two are marine epilithic from Bahia Concepcion, Dermocarpa sp. and Hyella sp. The third, Geitlerinema sp., occurs in thermal springs and in shrimp ponds, and the fourth, Tychonema sp., is from a shrimp pond. The partial sequences of the 16S rRNA genes and the phylogenetic relationship of four cyanobacterial strains (Synechococcus cf. elongatus, Leptolyngbya cf. thermalis, Leptolyngbya sp., and Geitlerinema sp.) are also presented. Polyphasic studies that include the combination of light microscopy, cultures and the comparative analysis of 16S rRNA gene sequences provide the most powerful approach currently available to establish the diversity of these oxygenic photosynthetic microorganisms in culture and in nature (AU)

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