Planta Piloto de Procesos Industriales Microbiológicos

Soybean disease loss estimates were compiled for the 1994 harvested crop from the 10 countries with the greatest soybean production. The objective was to document the major soybean disease problems in these countries and any recent changes in the severity of individual soybean diseases. Total yield losses caused by Heterodera glycines in these 10 countries were greater than those caused by any other disease. Next in order of importance were stem canker, brown spot, and charcoal rot. The total yield loss due to disease during 1994 in these countries was 14.99 million metric tons, valued at $3.31 billion. Methods used to estimate soybean disease losses were field surveys, plant disease diagnostic clinic samples, variety trial data, information from field workers and university extension staff, research plots, grower demonstrations, and private crop consultant reports. Yield loss estimates due to a particular disease varied by country. For example, yield losses due to rust were reported from China and Indonesia, but no losses due to this disease were reported from any of the remaining eight countries. Soybean disease control research and extension efforts are needed to provide more effective preventive and therapeutic disease management strategies and systems to producers.

and allied fusarioid genera (www.fusarium.org).

Soybean (Glycine max (L.) Merr.) disease loss estimates were compiled for the 1998 harvested crop from the top 10 soybean-producing countries in the world. These 10 countries (United States, Brazil, China, Argentina, India, Canada, Paraguay, Indonesia, Italy, and Bolivia) produced 97.6% of the world's total soybean crop in 1998. Total yield losses caused by soybean cyst [Heterodera glycines Ichinohe] in these 10 countries were greater than those caused by any other disease. Next in decreasing order of total yield reduction were brown spot [Septoria glycines (Hemmi)], charcoal rot [Macrophomina phaseolina (Tassi) Goidanich], and sclerotinia stem rot [Sclerotinia sclerotiorum (Lib.) de Bary]. The total yield loss due to diseases in these countries in 1998 was 28.5 × 106 t, valued at U.S. $6.29 × 109. Yield losses due to specific diseases varied by country. For example, yield losses due to rust were reported only from China and Indonesia. Soybean disease controls are needed to provide more effective preventive and therapeutic disease management strategies and systems to producers.

Anthropomorphically, an extreme environment is one in which physical conditions are not conducive for human life. In this review, extreme environments are defined as habitats that experience steady or fluctuating exposure to one or more environmental factors, such as salinity, osmolarity, desiccation, UV radiation, barometric pressure, pH, and temperature. Microorganisms that colonize extreme environments are called extremophiles, and they are categorized into subgroups according to the specific environmental characteristics of their habitats (for a review, see reference 78). Prokaryotic and eukaryotic microorganisms provide sources for the discovery of novel biochemical pathways and biomolecules that allow microbes to adapt to extreme environmental conditions. Previous studies of microorganisms from extreme environments have led to the development of important industrial processes and the discovery of health-promoting biomolecules. Examples include biochemicals used for detergent formulations, leather and paper processing, biofuels, bioremediation, UV-blocking, and new antibiotics (1, 17, 27, 28, 57, 93). Potentially beneficial biomolecules still remain to be discovered from unexplored extreme environments. One such environment is the high-altitude Andean wetland (HAAW) ecosystems of the South American Andes. The HAAW ecosystems are systems of shallow lakes formed during the Tertiary geological period. These aquatic ecosystems are distributed in the geographical area called the Puna at altitudes from 3,000 to 6,000 m above sea level, where they are isolated from direct human activity, and they are almost unexplored (Fig. 1). The HAAW ecosystems are unique not only for their geographical characteristics and broad range of extreme environments but also for their abundant biodiversity. The microbial communities that have evolved within these high-altitude aquatic ecosystems must tolerate chemical and physical stresses such as wide fluctuations in daily temperatures, hypersalinity, and variable pH and be adapted to high levels of UV radiation, a low level of nutrient availability, and high concentrations of heavy metals, especially arsenic (13, 14, 18, 19, 99). Polyphosphates (polyP), linear polymers of tens or hundreds of orthophosphate (Pi) residues linked by high-energy phosphoanhydride bonds, were apparently present on Earth before life appeared and were generated through a variety of abiotic processes (97). polyP have been associated with the capacity of microbes to resist both physical and chemical stresses (6, 39). The structural and physicochemical characteristics of polyP seem to have been criteria for the selection of these molecules as components of cellular processes during evolution (40). The early living organisms may have used polyP as long-term sources of Pi and energy. This may also have allowed microorganisms to survive Earth’s primitive environment, which resembled some of Earth’s current extreme environments. polyP granules or bodies (volutin granules, which stain red when treated with toluidine blue) are widely distributed among microbial species. Granules of polyP are homologous to the acidocalcisome, an organelle involved specifically in the storage and metabolism of cellular polyP (15). The association of acidocalcisomes with phosphorous metabolism and evidence that links polyP with the capacity of bacteria to overcome stress are of increasing scientific interest. polyP are some of the first examples of membrane-bound organelles with important functional roles found in both prokaryotic and eukaryotic kingdoms. This minireview will focus on the ways that polyP, biologically versatile molecules, could be involved in the adaptation to extreme environments by modulating microbial stress responses in pristine HAAW ecosystems. These aquatic ecosystems are natural laboratories for exploring and monitoring in situ interactions between the environment and the dynamics of biodiversity. to survive Earth’s primitive environment, which resembled some of Earth’s current extreme environments. polyP granules or bodies (volutin granules, which stain red when treated with toluidine blue) are widely distributed among microbial species. Granules of polyP are homologous to the acidocalcisome, an organelle involved specifically in the storage and metabolism of cellular polyP (15). The association of acidocalcisomes with phosphorous metabolism and evidence that links polyP with the capacity of bacteria to overcome stress are of increasing scientific interest. polyP are some of the first examples of membrane-bound organelles with important functional roles found in both prokaryotic and eukaryotic kingdoms. This minireview will focus on the ways that polyP, biologically versatile molecules, could be involved in the adaptation to extreme environments by modulating microbial stress responses in pristine HAAW ecosystems. These aquatic ecosystems are natural laboratories for exploring and monitoring in situ interactions between the environment and the dynamics of biodiversity. bonds, were apparently present on Earth before life appeared and were generated through a variety of abiotic processes (97). polyP have been associated with the capacity of microbes to resist both physical and chemical stresses (6, 39). The structural and physicochemical characteristics of polyP seem to have been criteria for the selection of these molecules as components of cellular processes during evolution (40). The early living organisms may have used polyP as long-term sources of Pi and energy. This may also have allowed microorganisms to survive Earth’s primitive environment, which resembled some of Earth’s current extreme environments. polyP granules or bodies (volutin granules, which stain red when treated with toluidine blue) are widely distributed among microbial species. Granules of polyP are homologous to the acidocalcisome, an organelle involved specifically in the storage and metabolism of cellular polyP (15). The association of acidocalcisomes with phosphorous metabolism and evidence that links polyP with the capacity of bacteria to overcome stress are of increasing scientific interest. polyP are some of the first examples of membrane-bound organelles with important functional roles found in both prokaryotic and eukaryotic kingdoms. This minireview will focus on the ways that polyP, biologically versatile molecules, could be involved in the adaptation to extreme environments by modulating microbial stress responses in pristine HAAW ecosystems. These aquatic ecosystems are natural laboratories for exploring and monitoring in situ interactions between the environment and the dynamics of biodiversity. to survive Earth’s primitive environment, which resembled some of Earth’s current extreme environments. polyP granules or bodies (volutin granules, which stain red when treated with toluidine blue) are widely distributed among microbial species. Granules of polyP are homologous to the acidocalcisome, an organelle involved specifically in the storage and metabolism of cellular polyP (15). The association of acidocalcisomes with phosphorous metabolism and evidence that links polyP with the capacity of bacteria to overcome stress are of increasing scientific interest. polyP are some of the first examples of membrane-bound organelles with important functional roles found in both prokaryotic and eukaryotic kingdoms. This minireview will focus on the ways that polyP, biologically versatile molecules, could be involved in the adaptation to extreme environments by modulating microbial stress responses in pristine HAAW ecosystems. These aquatic ecosystems are natural laboratories for exploring and monitoring in situ interactions between the environment and the dynamics of biodiversity. i) residues linked by high-energy phosphoanhydride bonds, were apparently present on Earth before life appeared and were generated through a variety of abiotic processes (97). polyP have been associated with the capacity of microbes to resist both physical and chemical stresses (6, 39). The structural and physicochemical characteristics of polyP seem to have been criteria for the selection of these molecules as components of cellular processes during evolution (40). The early living organisms may have used polyP as long-term sources of Pi and energy. This may also have allowed microorganisms to survive Earth’s primitive environment, which resembled some of Earth’s current extreme environments. polyP granules or bodies (volutin granules, which stain red when treated with toluidine blue) are widely distributed among microbial species. Granules of polyP are homologous to the acidocalcisome, an organelle involved specifically in the storage and metabolism of cellular polyP (15). The association of acidocalcisomes with phosphorous metabolism and evidence that links polyP with the capacity of bacteria to overcome stress are of increasing scientific interest. polyP are some of the first examples of membrane-bound organelles with important functional roles found in both prokaryotic and eukaryotic kingdoms. This minireview will focus on the ways that polyP, biologically versatile molecules, could be involved in the adaptation to extreme environments by modulating microbial stress responses in pristine HAAW ecosystems. These aquatic ecosystems are natural laboratories for exploring and monitoring in situ interactions between the environment and the dynamics of biodiversity. to survive Earth’s primitive environment, which resembled some of Earth’s current extreme environments. polyP granules or bodies (volutin granules, which stain red when treated with toluidine blue) are widely distributed among microbial species. Granules of polyP are homologous to the acidocalcisome, an organelle involved specifically in the storage and metabolism of cellular polyP (15). The association of acidocalcisomes with phosphorous metabolism and evidence that links polyP with the capacity of ba

Acinetobacter johnsonii A2 isolated from the natural community of Laguna Azul (Andean Mountains at 4,560 m above sea level), Serratia marcescens MF42, Pseudomonas sp. strain MF8 isolated from the planktonic community, and Cytophaga sp. strain MF7 isolated from the benthic community from Laguna Pozuelos (Andean Puna at 3,600 m above sea level) were subjected to UV-B (3,931 J m-2) irradiation. In addition, a marine Pseudomonas putida strain, 2IDINH, and a second Acinetobacter johnsonii strain, ATCC 17909, were used as external controls. Resistance to UV-B and kinetic rates of light-dependent (UV-A [315 to 400 nm] and cool white light [400 to 700 nm]) and -independent reactivation following exposure were determined by measuring the survival (expressed as CFU) and accumulation of cyclobutane pyrimidine dimers (CPD). Significant differences in survival after UV-B irradiation were observed: Acinetobacter johnsonii A2, 48%; Acinetobacter johnsonii ATCC 17909, 20%; Pseudomonas sp. strain MF8, 40%; marine Pseudomonas putida strain 2IDINH, 12%; Cytophaga sp. strain MF7, 20%; and Serratia marcescens, 21%. Most bacteria exhibited little DNA damage (between 40 and 80 CPD/Mb), except for the benthic isolate Cytophaga sp. strain MF7 (400 CPD/Mb) and Acinetobacter johnsonii ATCC 17909 (160 CPD/Mb). The recovery strategies through dark and light repair were different in all strains. The most efficient in recovering were both Acinetobacter johnsonii A2 and Cytophaga sp. strain MF7; Serratia marcescens MF42 showed intermediate recovery, and in both Pseudomonas strains, recovery was essentially zero. The UV-B responses and recovery abilities of the different bacteria were consistent with the irradiation levels in their native environment.

We describe stromatolites forming at an altitude of 3570 m at the shore of a volcanic lake Socompa, Argentinean Andes. The water at the site of stromatolites formation is alkaline, hypersaline, rich in inorganic nutrients, very rich in arsenic, and warm (20-24°C) due to a hydrothermal input. The stromatolites do not lithify, but form broad, rounded and low-domed bioherms dominated by diatom frustules and aragonite micro-crystals agglutinated by extracellular substances. In comparison to other modern stromatolites, they harbour an atypical microbial community characterized by highly abundant representatives of Deinococcus-Thermus, Rhodobacteraceae, Desulfobacterales and Spirochaetes. Additionally, a high proportion of the sequences that could not be classified at phylum level showed less than 80% identity to the best hit in the NCBI database, suggesting the presence of novel distant lineages. The primary production in the stromatolites is generally high and likely dominated by Microcoleus sp. Through negative phototaxis, the location of these cyanobacteria in the stromatolites is controlled by UV light, which greatly influences their photosynthetic activity. Diatoms, dominated by Amphora sp., are abundant in the anoxic, sulfidic and essentially dark parts of the stromatolites. Although their origin in the stromatolites is unclear, they are possibly an important source of anaerobically degraded organic matter that induces in situ aragonite precipitation. To the best of our knowledge, this is so far the highest altitude with documented actively forming stromatolites. Their generally rich, diverse and to a large extent novel microbial community likely harbours valuable genetic and proteomic reserves, and thus deserves active protection. Furthermore, since the stromatolites flourish in an environment characterized by a multitude of extremes, including high exposure to UV radiation, they can be an excellent model system for studying microbial adaptations under conditions that, at least in part, resemble those during the early phase of life evolution on Earth.

Microorganisms participate in both the manufacture and spoilage of foodstuffs. In Food Microbiology Protocols, expert laboratorians present a wide ranging set of detailed techniques for investigating the nature, products, and extent of these important microorganisms. The methods cover pathogenic organisms that cause spoilage, microorganisms in fermented foods, and microorganisms producing metabolites that affect the flavor or nutritive value of foods. Included in the section dealing with fermented foods are procedures for the maintenance of lactic acid bacteria, the isolation of plasmid and genomic DNA from species Lactobacillus, and the determination of proteolytic activity of lactic acid bacteria. A substantial number of chapters are devoted to yeasts, their use in food and beverage production, and techniques for improving industrially important strains. There are also techniques for the conventional and molecular identification of spoilage organisms and pathogens, particularly bacteria, yeasts, and the molds that cause the degradation of poultry products. Each method is described step-by-step for assured results, and includes tips on avoiding pitfalls or developing extensions for new systems.. Comprehensive and timely, Food Microbiology Protocols is a gold-standard collection of readily reproducible techniques essential for the study of the wide variety of microorganisms involved in food production, quality, storage, and preservation today

Biological control has been the most commonly researched control tactic within fruit fly management programs. For the first time, a review is carried out covering parasitoids and predators of fruit flies (Tephritidae) from the Americas and Hawaii, presenting the main biological control programs in this region. In this work, 31 species of fruit flies of economic importance are considered in the genera Anastrepha (11), Rhagoletis (14), Bactrocera (4), Ceratitis (1), and Zeugodacus (1). In this study, a total of 79 parasitoid species of fruit flies of economic importance are listed and, from these, 50 are native and 29 are introduced. A total of 56 species of fruit fly predators occur in the Americas and Hawaii.

This work provides quantitative information on Cr(VI) reduction in soil samples by an indigenous actinomycete. Streptomyces sp. MC1, previously isolated from sugarcane, has shown ability to reduce Cr(VI) in liquid minimal medium. A reduction of 100 and 75% was obtained at initial Cr(VI) concentrations of 5 and 50 mg l(-1), respectively, after 48 h of incubation. Bioremediation ability of Streptomyces sp. MC1 was assayed in soil extracts and soil samples. Relative growth of Streptomyces sp. MC1 was 77 and 38% when grown in soil extract with 10 and 50 mg l(-1) of Cr(VI), respectively. MC1 was able to reduce 30% of Cr(VI) after 96 h of incubation with 10 mg l(-1) of Cr(VI), and reduction coincided with the exponential growth phase at pH 7 and 30 degrees C.In soil samples, Streptomyces sp. MC1 was able to reduce up to 94% of the Cr(VI) bioavailability (50 mg kg(-1)) after 7 d. These results were compared with non-inoculated soil samples with Cr(VI). Bioremediation activity of Streptomyces sp. MC1 was not inhibited by natural soil microbial flora. Besides, Streptomyces sp. MC1 growth was not inhibited by 50 mg kg(-1) of Cr(VI). In contrast to findings obtained by other authors, our results showed almost complete Cr(VI) removal from soil without any previous treatment, and without addition of any substrate and with a normal soil humidity level. These results confirm the Cr(VI)-contaminated soil bioremediation potential of Streptomyces sp. MC1.

Synthetic petroleum-based polymers and natural plant polymers have the disadvantage of restricted sources, in addition to the non-biodegradability of the former ones. In contrast, eco-sustainable microbial polysaccharides, of low-cost and standardized production, represent an alternative to address this situation. With a strong global market, they attracted worldwide attention because of their novel and unique physico-chemical properties as well as varied industrial applications, and many of them are promptly becoming economically competitive. Scleroglucan, a β-1,3-β-1,6-glucan secreted by Sclerotium fungi, exhibits high potential for commercialization and may show different branching frequency, side-chain length, and/or molecular weight depending on the producing strain or culture conditions. Water-solubility, viscosifying ability and wide stability over temperature, pH and salinity make scleroglucan useful for different biotechnological (enhanced oil recovery, food additives, drug delivery, cosmetic and pharmaceutical products, biocompatible materials, etc.), and biomedical (immunoceutical, antitumor, etc.) applications. It can be copiously produced at bioreactor scale under standardized conditions, where a high exopolysaccharide concentration normally governs the process optimization. Operative and nutritional conditions, as well as the incidence of scleroglucan downstream processing will be discussed in this chapter. The relevance of using standardized inocula from selected strains and experiences concerning the intricate scleroglucan scaling-up will be also herein outlined.

Arsenic metabolism is proposed to be an ancient mechanism in microbial life. Different bacteria and archaea use detoxification processes to grow under high arsenic concentration. Some of them are also able to use arsenic as a bioenergetic substrate in either anaerobic arsenate respiration or chemolithotrophic growth on arsenite. However, among the archaea, bioenergetic arsenic metabolism has only been found in the Crenarchaeota phylum. Here we report the discovery of haloarchaea (Euryarchaeota phylum) biofilms forming under the extreme environmental conditions such as high salinity, pH and arsenic concentration at 4589 m above sea level inside a volcano crater in Diamante Lake, Argentina. Metagenomic analyses revealed a surprisingly high abundance of genes used for arsenite oxidation (aioBA) and respiratory arsenate reduction (arrCBA) suggesting that these haloarchaea use arsenic compounds as bioenergetics substrates. We showed that several haloarchaea species, not only from this study, have all genes required for these bioenergetic processes. The phylogenetic analysis of aioA showed that haloarchaea sequences cluster in a novel and monophyletic group, suggesting that the origin of arsenic metabolism in haloarchaea is ancient. Our results also suggest that arsenite chemolithotrophy likely emerged within the archaeal lineage. Our results give a broad new perspective on the haloarchaea metabolism and shed light on the evolutionary history of arsenic bioenergetics.

Economic losses caused by postharvest diseases represent one of the main problems of the citrus industry worldwide. The major diseases affecting citrus are the "green mold" and "blue mold", caused by Penicillium digitatum and P. italicum, respectively. To control them, synthetic fungicides are the most commonly used method. However, often the emergence of resistant strains occurs and their use is becoming more restricted because of toxic effects and environmental pollution they generate, combined with trade barriers to international markets. The aim of this work was to isolate indigenous killer yeasts with antagonistic activity against fungal postharvest diseases in lemons, and to determine their control efficiency in in vitro and in vivo assays. Among 437 yeast isolates, 8.5% show to have a killer phenotype. According to molecular identification, based on the 26S rDNA D1/D2 domain sequences analysis, strains were identified belonging to the genera Saccharomyces, Wickerhamomyces, Kazachstania, Pichia, Candida and Clavispora. Killers were challenged with pathogenic molds and strains that caused the maximum in vitro inhibition of P. digitatum were selected for in vivo assays. Two strains of Pichia and one strain of Wickerhamomyces depicted a significant protection (p <0.05) from decay by P. digitatum in assays using wounded lemons. Thus, the native killer yeasts studied in this work showed to be an effective alternative for the biocontrol of postharvest fungal infections of lemons and could be promising agents for the development of commercial products for the biological control industry.

Abstract We describe the techniques used to colonize and domesticate seven native New World species of hymenopterous parasitoids that attack flies within the genus Anastrepha (Diptera: Tephritidae). All parasitoid species successfully developed on artificially reared Mexican fruit fly, Anastrepha ludens (Loew) larvae or pupae. The parasitoid species colonized were the following: Doryctobracon areolatus (Szépligeti), Doryctobracon crawfordi (Viereck), Opius hirtus (Fischer), Utetes anastrephae (Viereck) (all Braconidae, Opiinae), Aganaspis pelleranoi (Bréthes) and Odontosema anastrephae Borgmeier (both Figitidae, Eucoilinae) (all larval-pupal parasitoids), and the pupal parasitoid Coptera haywardi (Ogloblin) (Diapriidae, Diapriinae). We provide detailed descriptions of the different rearing techniques used throughout the domestication process to help researchers elsewhere to colonize local parasitoids. We also describe handling procedures such as number of hosts in parasitization units and compare optimal host and female age, differences in parasitism rate, developmental time, life expectancy and variation in sex ratios in each parasitoid species over various generations. In the case of D. crawfordi and C. haywardi we also provide partial information on mass-rearing techniques such as cage type, parasitization unit, larval irradiation dose and adult handling.

ABSTRACT The Malvinas Basin is one of the few basins on the Argentine continental shelf that contains a proven petroleum system; however, uneconomical oil discoveries keep the basin at a frontier exploration status. The Malvinas Basin evolved through three main tectonic phases: rift, sag, and foredeep. The sedimentary fill of the basin is closely related to its tectonic history. Middle Jurassic rifting resulted in north-northwest–oriented grabens that filled with volcanic and pyroclastic continental rocks. Diminished faulting and generalized subsidence during the Late Jurassic–Neocomian early sag phase were accompanied by deposition of a basal transgressive marine wedge. The Aptian– Maastrichtian interval was characterized by tectonic quiescence and deposition of offshore mud-prone sediments. Southerly localized early Paleogene transtensional tectonism accompanied the early development of a foredeep trough. Outer shelf glauconite-rich sandstones, basinal claystones, and localized carbonate buildups partially filled the basin. By the middle Eocene–Oligocene, a strong deepening event marked the initiation of the fore-deep sensu stricto phase. This phase resulted in the full development of the Malvinas foredeep and the formation of compressional structures in the foreland. The foredeep basin was replenished by a westerly derived offlapping siliciclastic wedge of Oligocene–Miocene age. Noncommercial hydrocarbon discoveries in 5 of the 17 wells drilled in the basin suggest the presence of an undercharged Lower Inoceramus– Springhill petroleum system.

The Central Andes region displays unexplored ecosystems of shallow lakes and salt flats at mean altitudes of 3700 m. Being isolated and hostile, these so-called "High-Altitude Andean Lakes" (HAAL) are pristine and have been exposed to little human influence. HAAL proved to be a rich source of microbes showing interesting adaptations to life in extreme settings (poly-extremophiles) such as alkalinity, high concentrations of arsenic and dissolved salts, intense dryness, large daily ambient thermal amplitude, and extreme solar radiation levels. This work reviews HAAL microbiodiversity, taking into account different microbial niches, such as plankton, benthos, microbial mats and microbialites. The modern stromatolites and other microbialites discovered recently at HAAL are highlighted, as they provide unique modern-though quite imperfect-analogs of environments proxy for an earlier time in Earth's history (volcanic setting and profuse hydrothermal activity, low atmospheric O2 pressure, thin ozone layer and high UV exposure). Likewise, we stress the importance of HAAL microbes as model poly-extremophiles in the study of the molecular mechanisms underlying their resistance ability against UV and toxic or deleterious chemicals using genome mining and functional genomics. In future research directions, it will be necessary to exploit the full potential of HAAL poly-extremophiles in terms of their biotechnological applications. Current projects heading this way have yielded detailed molecular information and functional proof on novel extremoenzymes: i.e., DNA repair enzymes and arsenic efflux pumps for which medical and bioremediation applications, respectively, are envisaged. But still, much effort is required to unravel novel functions for this and other molecules that dwell in a unique biological treasure despite its being hidden high up, in the remote Andes.

We combined nucleic acid-based molecular methods, biogeochemical measurements, and physicochemical characteristics to investigate microbial sedimentary ecosystems of Laguna Tebenquiche, Atacama Desert, Chile. Molecular diversity, and biogeochemistry of hypersaline microbial mats, rhizome-associated concretions, and an endoevaporite were compared with: The V4 hypervariable region of the 16S rRNA gene was amplified by pyrosequencing to analyze the total microbial diversity (i.e., bacteria and archaea) in bulk samples, and in addition, in detail on a millimeter scale in one microbial mat and in one evaporite. Archaea were more abundant than bacteria. Euryarchaeota was one of the most abundant phyla in all samples, and particularly dominant (97% of total diversity) in the most lithified ecosystem, the evaporite. Most of the euryarchaeal OTUs could be assigned to the class Halobacteria or anaerobic and methanogenic archaea. Planctomycetes potentially also play a key role in mats and rhizome-associated concretions, notably the aerobic organoheterotroph members of the class Phycisphaerae. In addition to cyanobacteria, members of Chromatiales and possibly the candidate family Chlorotrichaceae contributed to photosynthetic carbon fixation. Other abundant uncultured taxa such as the candidate division MSBL1, the uncultured MBGB, and the phylum Acetothermia potentially play an important metabolic role in these ecosystems. Lithifying microbial mats contained calcium carbonate precipitates, whereas endoevoporites consisted of gypsum, and halite. Biogeochemical measurements revealed that based on depth profiles of O2 and sulfide, metabolic activities were much higher in the non-lithifying mat (peaking in the least lithified systems) than in lithifying mats with the lowest activity in endoevaporites. This trend in decreasing microbial activity reflects the increase in salinity, which may play an important role in the biodiversity.

Here we present the first culture‐independent microbiological and biogeochemical study of the mineral soils from 6000 m above sea level (m.a.s.l.) on some the highest volcanoes in the Atacama region of Argentina and Chile. These soils experience some of the harshest environmental conditions on Earth including daily temperature fluctuations across the freezing point (with an amplitude of up to 70°C) and intense solar radiation. Soil carbon and water levels are among the lowest yet measured for a terrestrial ecosystem and enzyme activity was near or below detection limits for all microbial enzymes measured. The soil microbial communities were among the simplest yet studied in a terrestrial environment and contained novel Bacteria and Fungi and only one Archaeal phylotype. No photosynthetic organisms were detected but several of the dominant bacterial phylotypes are related to organisms involved in carbon monoxide oxidation on other volcanoes (e.g., Pseudonocardia and Ktedonobacter spp.). Focused studies of a gene responsible for carbon monoxide oxidation, the large subunit of carbon monoxide dehydrogenase ( coxL of CODH), revealed several novel lineages and a broad diversity of coxL genes. Overall our results suggest that a unique microbial community, sustained by diffuse atmospheric and volcanic gases, is barely functioning on these volcanoes, which represent the highest terrestrial ecosystems yet studied.

Pesticides are normally used to control specific pests and to increase the productivity in crops; as a result, soils are contaminated with mixtures of pesticides. In this work, the ability of Streptomyces strains (either as pure or mixed cultures) to remove pentachlorophenol and chlorpyrifos was studied. The antagonism among the strains and their tolerance to the toxic mixture was evaluated. Results revealed that the strains did not have any antagonistic effects and showed tolerance against the pesticides mixture. In fact, the growth of mixed cultures was significantly higher than in pure cultures. Moreover, a pure culture (Streptomyces sp. A5) and a quadruple culture had the highest pentachlorophenol removal percentages (10.6% and 10.1%, resp.), while Streptomyces sp. M7 presented the best chlorpyrifos removal (99.2%). Mixed culture of all Streptomyces spp. when assayed either as free or immobilized cells showed chlorpyrifos removal percentages of 40.17% and 71.05%, respectively, and for pentachlorophenol 5.24% and 14.72%, respectively, suggesting better removal of both pesticides by using immobilized cells. These results reveal that environments contaminated with mixtures of xenobiotics could be successfully cleaned up by using either free or immobilized cultures of Streptomyces, through in situ or ex situ remediation techniques.

Azospirillum brasilense (strains REC3, RLC1, PEC5) were root inoculated in strawberry plants of the cultivars ‘Milsei’, ‘Selva’ and ‘Camarosa’ to assess plant growth-promoting effects. The bacteria were able to promote plant growth (expressed as root length, root area, and dry weight of root and shoot), depending on the genotypes of plants and bacteria used, whereas the stolon production (3–4) depended only on the strawberry cultivar. To explain whether root exudates plays any role on the growth-promotion observed herein, total protein and sugar were determined, and chemotaxis properties were evaluated. The strains showed positive chemotaxis toward the root exudates, being influenced by the total sugars content, suggesting that the latter plays an important role in the chemotaxis effect and may contribute to enhance the root capacity to recruit azospirilla from rhizosphere, thus improving the growth-promoting effect exerted by these bacteria.

Summary Citrus is an economically important fruit crop that is severely afflicted by citrus canker, a disease caused by the bacterial phytopathogen, Xanthomonas citri subsp. citri ( Xcc ). GenBank houses a large collection of Expressed Sequence Tags (ESTs) enriched with transcripts generated during the defence response against this pathogen; however, there are currently no strategies in citrus to assess the function of candidate genes. This has greatly limited research as defence signalling genes are often involved in multiple pathways. In this study, we demonstrate the efficacy of RNA interference (RNAi) as a functional genomics tool to assess the function of candidate genes involved in the defence response of Citrus limon against the citrus canker pathogen. Double‐stranded RNA expression vectors, encoding hairpin RNAs for citrus host genes, were delivered to lemon leaves by transient infiltration with transformed Agrobacterium . As proof of principle, we have established silencing of citrus phytoene desaturase ( PDS) and callose synthase ( CalS1 ) genes. Phenotypic and molecular analyses showed that silencing vectors were functional not only in lemon plants but also in other species of the Rutaceae family. Using silencing of CalS1 , we have demonstrated that plant cell wall‐associated defence is the principal initial barrier against Xanthomonas infection in citrus plants. Additionally, we present here results that suggest that H 2 O 2 accumulation, which is suppressed by xanthan from Xcc during pathogenesis, contributes to inhibition of xanthan‐deficient Xcc mutant growth either in wild‐type or CalS1 ‐silenced plants. With this work, we have demonstrated that high‐throughput reverse genetic analysis is feasible in citrus.