Analía Alvarez

Actinobacteria: Current research and perspectives for bioremediation of pesticides and heavy metals

Actinobacteria exhibit cosmopolitan distribution since their members are widely distributed in aquatic and terrestrial ecosystems. In the environment they play relevant ecological roles including recycling of substances, degradation of complex polymers, and production of bioactive molecules. Biotechnological potential of actinobacteria in the environment was demonstrated by their ability to remove organic and inorganic pollutants. This ability is the reason why actinobacteria have received special attention as candidates for bioremediation, which has gained importance because of the widespread release of contaminants into the environment. Among organic contaminants, pesticides are widely used for pest control, although the negative impact of these chemicals in the environmental balance is increasingly becoming apparent. Similarly, the extensive application of heavy metals in industrial processes lead to highly contaminated areas worldwide. Several studies focused in the use of actinobacteria for cleaning up the environment were performed in the last 15 years. Strategies such as bioaugmentation, biostimulation, cell immobilization, production of biosurfactants, design of defined mixed cultures and the use of plant-microbe systems were developed to enhance the capabilities of actinobacteria in bioremediation. In this review, we compiled and discussed works focused in the study of different bioremediation strategies using actinobacteria and how they contributed to the improvement of the already existing strategies. In addition, we discuss the importance of omic studies to elucidate mechanisms and regulations that bacteria use to cope with pollutant toxicity, since they are still little known in actinobacteria. A brief account of sources and harmful effects of pesticides and heavy metals is also given.

Fall Armyworm Strains (Lepidoptera: Noctuidae) in Argentina, Their Associate Host Plants and Response to Different Mortality Factors in Laboratory

Abstract The aim of this research was to identify the existence of different Spodoptera frugiperda (J.E. Smith) (FAW) host strains in Argentina, and to determine their behaviors in the presence of different mortality factors. Populations belonging to these strains were tested with the pesticides chlorpyriphos and cypermethrin, transgenic corn germplasms expressing Cry proteins 1Ab or 1F, and an indigenous Bacillus thuringiensis strain. The relation of these strains with the host plant species and crop utilization, subsistence or commercial ones, is discussed. The response to the assayed insecticides, Bt transgenic corn and Bt suspension was diverse, showing wide variability in mortality rates. This research validates the need of intensive studies relating resistance phenomena with the differential behavior of the host strains inhabiting Argentina. Host plant and crop utility is not a determinant for the identity of the colonizing strain, so molecular identification of the strains is highly recommended before study of any aspect of the FAW in Argentina.

Heavy metal resistant strains are widespread along Streptomyces phylogeny

The genus Streptomyces comprises a group of bacteria species with high economic importance. Several of these species are employed at industrial scale for the production of useful compounds. Other characteristic found in different strains within this genus is their capability to tolerate high level of substances toxic for humans, heavy metals among them. Although several studies have been conducted in different species of the genus in order to disentangle the mechanisms associated to heavy metal resistance, little is known about how they have evolved along Streptomyces phylogeny. In this study we built the largest Streptomyces phylogeny generated up to date comprising six genes, 113 species of Streptomyces and 27 outgroups. The parsimony-based phylogenetic analysis indicated that (i) Streptomyces is monophyletic and (ii) it appears as sister clade of a group formed by Kitasatospora and Streptacidiphilus species, both genera also monophyletic. Streptomyces strains resistant to heavy metals are not confined to a single lineage but widespread along Streptomyces phylogeny. Our result in combination with genomic, physiological and biochemical data suggest that the resistance to heavy metals originated several times and by different mechanisms in Streptomyces history.

Lindane removal using Streptomyces strains and maize plants: a biological system for reducing pesticides in soils

Background and aimsPlants and contaminant-degrading microbes are a suitable combination for the remediation of pesticides. The aim of this study was to evaluate the effectiveness of Streptomyces strains cultured with maize plants in relation to lindane removal.MethodsFour Streptomyces strains were cultured and added as both single and mixed cultures, along with maize plants, to artificially polluted hydroponic systems and soils. The effectiveness of the resulting soil bioremediation was then evaluated through phytotoxicity testing using lettuce seedlings.ResultsIn the hydroponic and soil experiments, similar levels of lindane removal were recorded in the inoculated and non-inoculated systems where maize plants were introduced. However, the vigor index (VI) of the maize plants was highest when grown in inoculated and artificially polluted soil. In the phytotoxicity assay, the VI of the lettuce seedlings increased with increasing bioremediation time for the soils, thus indicating the effectiveness of the process.ConclusionsSimilar levels of lindane removal were recorded in both inoculated and non-inoculated planted systems, indicating that pesticide removal was not significantly affected by the bacterial inoculant. However, inoculation an actinobacteria consortium led to an increase in the VI of the maize and protected the plants against the existing toxicity. Furthermore, maize plants may attenuate the transient toxic effects of microbial lindane degradation.

Characterization of native Bacillus thuringiensis strains and selection of an isolate active against Spodoptera frugiperda and Peridroma saucia.

Twelve Bacillus thuringiensis (Bt) strains, isolated from larvae and soil samples in Argentina, were molecularly and phenotypically characterized and their insecticidal activities against Spodoptera frugiperda and Peridroma saucia were determined. One isolate—Bt RT—produced more than 93% mortality on first instar larvae of both species, which was higher than that produced by the reference strain Bt 4D1. Bt RT carried a different cry gene profile than Bt 4D1. Scanning electron microscopy showed the presence of bipyramidal and cuboidal crystals. Phenotypic characterization revealed lytic enzymes that could contribute to Bt pathogenicity.

Insecticidal crystal proteins from native Bacillus thuringiensis: numerical analysis and biological activity against Spodoptera frugiperda

Fourteen strains of Bacillus thuringiensis collected from both larvae showing disease symptoms and soil samples in northwest Argentina were characterized by insecticidal activity against Spodoptera frugiperda. First instar larvae and protein profile SDS-PAGE analysis of whole cell proteins not only allowed the differentiation of native Bacillus thuringiensis but also revealed the possibility of applying protein profile analysis in classification of toxicity patterns. Cluster analysis showed that there were two main groups. Interestingly, one of them only contained the most pathogenic native strains. The biomass-bound protease activity of native pathogenic isolates and the reference strain Bt 4D1 is also reported.

Use of Actinobacteria Consortia to Improve Methoxychlor Bioremediation in Different Contaminated Matrices

Methoxychlor (MTX) is an organochlorine pesticide which has been banned in most countries; however, it is still being used in agricultural products and against mosquito. This pesticide has estrogenic activity and mimics endocrine hormone functions. Thus, it is important to analyze its behavior in different matrices.

Bioremediation in Latin America

According to the Merriam-Webster dictionary definition, agriculture is “the science, art, or practice of cultivating the soil, producing crops, and raising livestock, and in varying degrees the preparation and marketing of the resulting products.” As it is, even though this definition is very comprehensive, there is more than meets the eye about the universe of activities involved in agronomic practices. Agriculture is witness to many changes since its dawning, evolving from animal and seed domestication to genetic modification of organisms through molecular biology techniques to better suit worldwide demand. These changes influenced land ownership as well as technology development. Different climatic and anthropological realities generate diverse productive systems that adapt to every situation. Developing countries with less appropriate technologies for industrialization have large rural populations where peasant economies are sometimes critical for subsistence. Despite all the benefits of agriculture, it sometimes faces drawbacks for proper production. Other times agriculture brings along sociopolitical and environmental problems. Cultural practices have detrimental impacts on soil quality and water availability. Moreover the environment is the ultimate recipient of pesticides, herbicides, fertilizers, and other by-products. Nonetheless bioremediation techniques involving plants and microorganisms are in constant development to try to decrease the negative effects of farming, bringing these emerging processes new options for a better management in agriculture. N. Romano-Armada • V.B. Rajal (*) Instituto de Investigaciones para la Industria Química (INIQUI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Universidad Nacional de Salta (UNSa), Av. Bolivia 5150, 4400, Salta, Argentina Universidad Nacional de Salta (UNSa), Av. Bolivia 5150, 4400, Salta, Argentina e-mail: vbrajal@gmail.com M.J. Amoroso Planta Piloto de Procesos Industriales Microbiológicos (PROIMI), CONICET, Av. Belgrano y Pasaje Caseros, 4000 Tucumán, Argentina Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, 4400 Tucumán, Argentina Universidad del Norte Santo Tomás de Aquino (UNSTA), 4000 Tucumán, 4400 Tucumán, Argentina

Fungal decomposers of leaf litter from an invaded and native mountain forest of NW Argentina

The impact of plant species invasions on the abundance, composition and activity of fungal decomposers of leaf litter is poorly understood. In this study, we isolated and compared the relative abundance of ligninocellulolytic fungi of leaf litter mixtures from a native forest and a forest invaded by Ligustrum lucidum in a lower mountain forest of Tucuman, Argentina. In addition, we evaluated the relationship between the relative abundance of ligninocellulolytic fungi and properties of the soil of both forest types. Finally, we identified lignin degrading fungi and characterized their polyphenol oxidase activities. The relative abundance of ligninocellulolytic fungi was higher in leaf litter mixtures from the native forest. The abundance of cellulolytic fungi was negatively related with soil pH while the abundance of ligninolytic fungi was positively related with soil humidity. We identified fifteen genera of ligninolytic fungi; four strains were isolated from both forest types, six strains only from the invaded forest and five strains were isolated only from the native forest. The results found in this study suggest that L. Lucidum invasion could alter the abundance and composition of fungal decomposers. Long-term studies that include an analysis of the nutritional quality of litter are needed, for a more complete overview of the influence of L. Lucidum invasion on fungal decomposers and on leaf litter decomposition.

Characterization and Biological Activity of Bacillus thuringiensis Isolates that Are Potentially Useful in Insect Pest Control

© 2012 Alvarez and del Valle Loto, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Characterization and Biological Activity of Bacillus thuringiensis Isolates that Are Potentially Useful in Insect Pest Control