Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> https://scielo.conicyt.cl/rss.php?pid=0718-951620170004&lang=es vol. 17 num. 4 lang. es <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[<b>Microbial community structure and biomass of a mine soil with different organic and inorganic treatments and native plants</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400001&lng=es&nrm=iso&tlng=es Heavy metals far in excess of trace amounts that are required for healthy plant growth, cause harmful effects on soil microorganisms; however, studies concerning the characterization of microbial communities in mine soils are scarce. The present study is the first attempt to characterize, by means of the analysis of phospholipid fatty acid (PLFA) patterns, soil microbial community composition from a contaminated mine soil (Pb, As) subjected to different remediation technologies. A pot experiment was performed with a soil from the São Domingos mine (South of Portugal) with or without native herbaceous plants combined with the following soil treatments: control; inorganic fertilizer (NPK); inorganic fertilizer plus polyacrylate polymer; inorganic fertilizer plus organic amendment (compost); inorganic fertilizer plus both amendments (compost, polymer). The measurements of PLFA patterns were made on soil samples collected 5 months after the application of remediation treatments. The total microbial biomass and the biomass of specific groups increased notably after soil treatments, particularly those including organic amendments, and were significantly higher in presence of native plants than in the corresponding bare soils. The data also indicated that a plant cover rather than organic and inorganic treatments played the dominant role in determining the composition of the microbial community. An influence of different soil treatments on microbial composition was also observed; the effect of organic amendment being more pronounced than that of the remaining treatments. The results clearly showed the efficacy of a vegetation cover (native plants) combined with the use of organic amendment in the reclamation of this degraded mine soil. <![CDATA[<strong>Volatile organic compounds stimulate plant growing and seed germination of <i>Lactuca sativa</i></strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400002&lng=es&nrm=iso&tlng=es Volatile organic compounds (VOCs) emitted by Bacillus species have been reported as growth inducers in Arabidopsis thaliana, but their effects on horticultural species have been scarcely studied. In this study, Lactuca sativa emerges as a model vegetable to evaluate VOCs release by Bacillus sp. BCT9. The results indicated that root length, dry weight, number of lateral root and shoot length increased after VOCs exposition. The initial application of 30 µL of BCT9 in Nutrient Agar (N-A) was the best dose to elicit growth; whereas 60 µL of BCT9 inoculated in Methyl Red & Voges Proskauer Agar (MRVP-A) and Murashige & Skoog Agar (MS-A) had a greater effect. It noteworthy that root development was higher when BCT9 was grown in MRVP-A than in the others culture medium. The identified VOCs released by BCT9 in MRVP-A were 3-hydroxy-2-butanone, 2,3-butanediol, 2-nonanone, 2-undecanone, 2-tridecanone and 2-pentadecanone. Furthermore, the toxicity bioassays indicated that most VOCs did not have high toxic effects and some VOCs stimulated the growth at seed germination stage. In conclusion, this study suggests that VOCs can strongly modulate the L. sativa growth during germination and seedlings stages, so new explorations should be carried out in other vegetables to determine their effects. <![CDATA[<b>Strawberry monocropping</b>: <b>Impacts on fruit yield and soil microorganisms</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400003&lng=es&nrm=iso&tlng=es The objective of this work was to explore the impacts of intensive strawberry monocropping during five years on the fruit-yield and onthe microbial soil activity and composition. Field trials were performed in twoplots: P1 (a soil with five years of consecutive strawberry cropping), and P2 (asoil with just one year of strawberry cropping). Fruit-yield was quantified;total microorganisms and four functional groups (cellulolytics, nitrogen-fixers, phosphate solubilizers, and siderophores producers) were quantified, isolated and characterized in both plots. Total microbial activity was assessed by the hydrolysis of fluorescein-diacetate and soil respiration methods. As results, in P1, a 51 % decrease in fruit-yield was observed, whilein P2 it was closer to the yield obtained in P1 during the first and second year of cultivation. Total microbial number and activity were 23 % and 70% lower in P1 than in P2 at the end of the cropping, respectively. In general,the quantity of total culturable microorganisms and the functional group sanalyzed were significantly higher in P2 than in P1 (p< 0.05).The most prevailing bacteria putatively identified were Cellulosimicrobacterium cellulans, Paenibacillus sp., Azospirillum brasilense, and Burkholderia sp. According to our results, the intensive cultivation of strawberry for several years in the same field exerted a negative impact on the soil quality, affecting the native microbial population, which might be linked to the fruit yield decline. <![CDATA[<strong>Effects of biochar on nutrients and the microbial community structure of tobacco-planting soils</strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400004&lng=es&nrm=iso&tlng=es The effect of rice straw biochar on soil nutrients was studied using a randomized block experimental design in atobacco-planting field, and differences in soil bacterial and fungal community structures were studied using high-throughput sequencing technology. The results indicated that the soil pH, CEC, total organic carbon (TOC), inorganic carbon (IC), soil total nitrogen (total N), total potassium (total K), available phosphorus (available P), and available potassium (available K) contents were all increased with the biochar application. TOC and available P contents increased by 38.19% and 22.38%, respectively, in the T2 treatment (4500 kg·ha-1 biochar) compared to those in control (CK). But the soil dissolved organic carbon ( DOC) and available nitrogen (availableN)content decreased by 13.07% and 9.89% in T2 treatments compared to the CK, respectively. Soil bacteria composition mainly consisted of Proteobacteria, Actinobacteria, and Acidobacteria, and the Proteobacteria proportion represented >50% of the bacterial community. The Actinobacteria proportion decreased, but Proteobacteria and Acidobacteria proportions increased with increasing biochar amounts. Fungi in tobacco-planting soils were mainly Ascomycota (>75%), but this proportion decreased as the biochar amount increased. However, Zygomycota and Basidiomycota proportions increasedwithincreasing biochar amounts. Therefore, biochar application could improve the soil nutrient status and affect microbial community structure. Rice straw biochar application promoted fungal community diversity in tobacco-planting soils. <![CDATA[<b>Potassium solubilizing bacteria (KSB):</b>: <b>Mechanisms, promotion of plant growth, and future prospects ­ A review</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400005&lng=es&nrm=iso&tlng=es Potassium (K) is considered as an essential nutrient and a major constituent within all living cells. Naturally, soils contain K in larger amounts than any other nutrients; however most of the K is unavailable for plant uptake. Application of chemical fertilizers has a considerably negative impact on environmental sustainability. It is known that potassium solubilizing bacteria (KSB) can solubilize K-bearing minerals and convert the insoluble K to soluble forms of K available to plant uptake. Many bacteria such as Acidothiobacillus ferrooxidans, Paenibacillus spp., Bacillus mucilaginosus, B. edaphicus, and B. circulans have capacity to solubilize K minerals (e.g., biotite, feldspar, illite, muscovite, orthoclase, and mica). KSB are usually present in all soils, although their number, diversity and ability for K solubilization vary depending upon the soil and climatic conditions. KSB can dissolve silicate minerals and release K through the production of organic and inorganic acids, acidolysis, polysaccharides, complexolysis, chelation, and exchange reactions. Hence, the production and management of biological fertilizers containing KSB can be an effective alternative to chemical fertilizers. This article presents an overview of current trends and challenges on KSB, mechanisms and their role in plant growth promotion, and eventually gives some perspectives for research on K in agriculture. <![CDATA[<b>Biochar effects on nitrogen and phosphorus use efficiencies of zucchini plants grown in a calcareous sandy soil</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400006&lng=es&nrm=iso&tlng=es Biochar (B) application to sandy soils improves its productivity and mitigates climate change. A pot experiment was conducted to investigate the potential effects of maize stalks biochar applied to a zucchini (Cucurbita pepo L. var.Hybrid fadwa) grown on a calcareous sandy soil. Plastic pots were filed with three kilograms of the studied soil and amended by the biochar at levels of 0 (control, unamended soil), 6.3 (B1), 12.6 (B2), and 25.5 (B3) g pot‒1. The pots were planted with zucchini plants and designed in a complete randomized design with three replications. Amending the soil with the biochar significantly increased the soil organic matter, fresh fruit yield, nitrogen use effiency (NUE) and agronomic efficiency of applied nitrogen (AE N) of zucchiniplants. Biochar additions improved the fresh fruits by 26.7, 55, and 195.0 % for B1, B2 and B3 treatments respectively, over the control. The NUE of the plants increased owing to the application of biochar to the soil from 69.2 mg fruit/mg N at the control treatment to 77.1, 84.3 and 131.4 mg fruit/mg N for B1, B2 and B3 treatments, respectively. So, it is recommended to apply biochar as an amendment to the calcareous sandy soil in order to improve its fertility. <![CDATA[<strong>Acid tolerant <i>Rhizobium</i> strains contribute to increasing the yield and profitability of common bean in tropical soils</strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400007&lng=es&nrm=iso&tlng=es Symbiosis of common bean with nitrogen-fixing bacteria can lead to a reduction in production costs and in environmental impacts. Considering the diversity of soils and climates, it is important to validate bacterial strains under different conditions to consolidate their recommendation as inoculants. Studies concerning the economic viability of Rhizobium inoculation in common bean are few, but they could assist in choosing the strain to be adopted. The aim of this study was to evaluate the performance of Rhizobium strains isolated from acid soils from the Amazon inoculated in seeds of the BRSMG Madrepérola cultivar and to evaluate the economic viability of their use in the field. Four field experiments were conducted in the state of Minas Gerais, Brazil. A randomized block experimental design was used with four replications and seven treatments: inoculation with the strains CIAT 899 (Rhizobium tropici), UFLA 02-100 (R. etli), UFLA 02-68 (R. etli bv. mimosae), UFLA 02-127 (R. leguminosarum bv. phaseoli), and UFLA 04-173 (R. miluonense),plus two controls, one without inoculation + mineral nitrogen (N-urea) at a rate of 80 kg N ha-1 and another without inoculation and without mineral N. The strain CIAT 899 is already recommended for the manufacture of a commercial inoculant, and the others, collected in the Amazon Forest, have proven to be highly effective in biological nitrogen fixation. Symbiosis of common bean with all the strains evaluated leads to satisfactory yields, with reduction in the application rate of mineral nitrogen and in environmental impacts and, consequently, reduction in economic costs, with higher profitability. <![CDATA[<b>Ammonia-oxidizing microorganisms</b>: <b>key players in the promotion of plant growth</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400008&lng=es&nrm=iso&tlng=es Nitrogen (N) is the most important mineral nutrient required by plants. Although some plants can directly utilize N, ammonium (NH4+) and nitrate (NO3-) are the only forms of N that are usable to most plants. Ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) are the key drivers that are responsible for the conversion of N into usable forms. Due to the importance of ammonia oxidizers (AOs), factors affecting their abundance and activity have been a major research focus over the years. This review focuses on the diversity of AOs, the factors that affect their abundance and activity in different soil types and the mechanism of nitrification. An improved understanding of the combinatorial effects of highly active AOs and methods for limiting nitrate loss from soils may enhance the management of nitrate in soils and improve plant yields. <![CDATA[<b>Characterization of yeast in hapludands soil with biotechnological potential</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400009&lng=es&nrm=iso&tlng=es Yeasts play an important role in nature, and soil is one of the largest reservoirs of yeasts. Seventy-seven yeast strains were isolated from southern Chilean volcanic ash soil. These 77 strains were composed of 30 strains derived from soils used as permanent grassland, 30 strains from rotating grassland, and 17 strains from native forest (considered as the control). These strains were identified using restriction fragment length polymorphisms (PCR-RFLP) in conjunction with ITS-5.8S rDNA sequencing. Additionally, a physiological characterization of the assimilation of carbon and nitrogen and the fermentation of sugars was performed. Various features of the strains were evaluated including their growth in vinasse medium, nitrogen and phosphorus content, and lipid production. Lastly, the use of strains as biofertilizers was analyzed via the cultivation of bell pepper seedlings in soil. From the RFLP profiles, the 77 strains clustered into 10 groups. Of these, only three groups could be identified to the species level, and another was classified to the level of genus (Devaryomyces hansenii, Pichia fermentan, Kazachstania exigua, Candida sp.). All strains grew in vinasse medium. Six strains (PP1, PP4, PR4, PR10, PR27 and PR29) showed a high capacity to accumulate lipids, and three strains (PP1, PP21 and PR28) have the potential to be used as biofertilizers. <![CDATA[<b>Factors affecting arbuscular mycorrhizal fungi of Chilean temperate rainforests</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400010&lng=es&nrm=iso&tlng=es While arbuscular mycorrhizal (AM) fungi in Chile have been widely documented in agro-ecosystems, there is a knowledge gap regarding AM fungal diversity in Chilean temperate rainforests. AM fungal communities of these forests are affected by several factors: the mountain systems of Chile (Coastal Range or Andes Mountains), the mycorrhizal dominance of the forest (either ectomycorrhizal -EM- or AM), soil chemistry, and altitude. We tested the effects of mountain system, mycorrhizal dominance, soil chemistry, and altitude on AM fungal diversity. From 7,120 AM fungal spores recovered, we identified 14 species, that were found in 41 soil samples collected from 14 plots located in EM and AM forests of the Coastal Range and Andes Mountains of Southern Chile. Mountain system and mycorrhizal dominance affected AM fungal community composition, although neither fungal richness nor abundance were affected. Soil Olsen available P, Ca, Mg, and Na were the edaphic variables structuring AM fungal community composition. There was no relationship between altitude and AM fungal richness, however at high altitudes there was higher abundance. Finally, with this and other studies, a total of 59 AM fungal species, many of which were previously registered exclusively in agroecosystems, are registered on the Chilean AM fungal species list. <![CDATA[<b>Functional land-use change effects on soil fungal communities in Chilean temperate rainforests</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400011&lng=es&nrm=iso&tlng=es By reducing soil organic matter and litter input, land-use changes are predicted to decrease total soil fungal diversity, but at functional levels this have been poorly studied. It is expected, though, that increasing disturbance decreases saprotrophic and mycorrhizal fungi biodiversity. This study aimed to determine the effects of land-use changes on the phylogenetic and functional diversity of soil fungi in the Southern Andes. We assessed the fungal communities of Andosol topsoil at 1 cm and 10 cm soil depth. The soil samples were obtained from a gradient of anthropogenic disturbance; specifically, plots were located within pristine forest, overstory-managed, and clear-cut conditions. We used a cultivation-independent molecular barcoding approach to assess fungal diversity and identify 1,173 OTUs from which 401 were assigned to a functional guild. While we found higher phylogenetic richness in clear-cut conditions, these soils had higher relative abundances of plant pathogen fungi and lower relative abundances of saprotrophic and ectomycorrhizal fungi compared to the other treatments. The opposite pattern was found in pristine forest. Thus, fungal species richness itself does not seem to reflect ecosystem health. Interestingly though, the lower phylogenetic diversity found in pristine forest was compensated by a higher diversity of fungi involved in nutrient cycling. <![CDATA[<strong>Efficiency of two</strong> <strong>inoculation methods of <i>Pseudomonas putida</i> on growth and yield of tomato plants</strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400012&lng=es&nrm=iso&tlng=es The objective of this study was to determine the efficiency of applying microcapsules and liquid inoculation of three Pseudomonas putida strains on growth and yield of tomato plants in greenhouse where the results showed differences between both treatments. Rhizobacterial strainsFA-8, FA-56, and FA-60 of P. putida, were assessed individually and combined to determine their capacity to produce indoleacetic acid (IAA). The three strains demonstrated the capacity to produce IAAin vitro, of which FA-56 stood out with 23.02 µg mL-1 in the microcapsule treatment with significant increases in plant height, stem diameter, radical volume, dry biomass, fruit yield, and rhizobacterial population (CFU). These responses could have been associated to the intrinsic capacity of this strain to produce a greater amount of IAA, hormone related to promoting plant growth. The use of plant growth-promoting rhizobacteria (PGPR) as biofertilizers by means of microcapsules could be an alternative in agricultural management and sustainable production of tomato. Immobilization of P. putidarhizobacteria by alginate microcapsules confers protection and gradual release, improving adhesion, permanency, and colonization of cells on the roots, promoting a better effect as PGPR and productivity in tomato plants. <![CDATA[<b>Long-term phosphorus fertilization effects on arbuscular mycorrhizal fungal diversity in Uruguayan grasses</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400013&lng=es&nrm=iso&tlng=es Arbuscular mycorrhizas (AM) are particularly relevant in grasslands due to the high colonization in grasses, main constituent of this ecosystem. Natural grassland (NG) is the dominant ecosystem of Uruguay and it supports one of the main economic activities of the country: livestock. Available phosphorus (P) contents in NG soils of Uruguay are low, so phosphate fertilization is frequent. The aim of this work was to study the effect of phosphorus fertilization on arbuscular mycorrhizal fungi (AMF) diversity of two native grasses of Uruguay: Paspalum dilatatum and Coelorhachis selloana. Diversity and abundance of AMF spores in the rhizosphere of grasses were studied using morphological techniques, while AMF diversity in roots was studied through T-RFLP. The study was conducted in a long-term experiment of phosphorus fertilization in Uruguayan grasslands. The increase in available P did not affect the diversity of AMF in the roots or in the rhizosphere of the studied grasses. The richness of AMF biotypes in roots and spores abundance differed between host species, with higher values in C. selloana than in P. dilatatum. Differences in AMF diversity between seasons were observed, with greater number of biotypes in winter than in summer. <![CDATA[<b>Natives helping foreigners?</b>: <b>The effect of inoculation of poplar with patagonian beneficial microorganisms</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400014&lng=es&nrm=iso&tlng=es Inoculation with microorganisms represents an opportunity to enhance tree production, directly affecting plant growth or survival at planting. The aim of the present study was to evaluate the effect of mixed inoculation with native mycorrhizae, two yeasts and one endophytic bacterium, on the growth of two poplar clones commonly used in Patagonia, Argentina. Yeasts and bacteria were selected base on their ability to produce IAA and siderophores, as well as P solubilization in-vitro. A greenhouse trial was performed using hardwood cuttings of Populus nigra ,Italica, and Populus trichocarpa ,SP1456,. Only yeasts modified growth traits, in a host-related response: Tausonia pullulans reduced the root/shoot ratio in P. nigra, and Candida saitoana and increased shoot dry biomass in P. trichocarpa. All plants presented arbuscular mycorrhizal colonization but ectomycorrhizae were absent. Two types of arbuscular mycorrhizal colonization were observed, one of them similar to Glomus tenue. We found a tendency for a higher percentage of arbuscular mycorrhizal colonization when plants were inoculated with T. pullulans. The used of native yeast along with mycorrhizal inocula appears to be a promising tool to improve poplar forestry. <![CDATA[<b>Effectiveness of biofertilizer enriched in N by <i>Beijerinckia indica</i> on sugarcane grown on an Ultisol and the interactive effects between biofertilizer and sugarcane filter cake</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400015&lng=es&nrm=iso&tlng=es To improve yield and nutrient absorption, the addition of fertilizers to provide nutrients in adequate quantities is recommended. An alternative substitution for soluble fertilizer is the use of Acidithiobacillus bacteria to produce rock biofertilizer that is then mixed with organic matter inoculated with diazotrophic bacteria (Beijerinckia indica) for N enrichment. This study evaluates the effectiveness of biofertilizer on nutrient uptake and its interaction with sugarcane filter cake in field-grown sugarcane on an Ultisol in the Brazilian rainforest region. The experiment used two NPK fertilizer treatments (biofertilizer and soluble fertilizer) applied at three rates (50, 100 and 150% of the recommended rate [RR]) and a control treatment of earthworm compost (20 t ha-1). The fertilizer treatments were applied with and without filter cake, in four replicates. Total C and N, available P and K, and exchangeable Ca and Mg in plants (upper shoots, leaves and stems) as well as soil samples were analyzed. The biofertilizer showed similar responses as did the soluble fertilizer in nutrient uptake in the different parts of sugarcane and in the soil samples. The effects of biofertilizer were enhanced by the interaction of the fertilizer treatments with sugarcane filter cake. We concluded that the biofertilizer enriched in N by inoculation with B. indica may be a viable alternative for the replacement of soluble fertilizers in sugarcane. <![CDATA[<b>Salt and alkali stresses reduction in wheat by plant growth promoting haloalkaliphilic bacteria</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400016&lng=es&nrm=iso&tlng=es Haloalkaliphilic bacteria have plant growth promoting characteristics that can be used to deal with different environmental stresses. To study the effect of haloalkaliphilic bacteria to reduce salinity and alkalinity stress in wheat, 48 isolates were isolated and grouped into halophiles, alkaliphiles and haloalkaliphiles based on growth characteristics. The ammonia, 3-indole acetic acid and ACC (1-aminocyclopropane-1-carboxylate) deaminase production were studied. Wheat yield was evaluated in the presence of six plant growth promoting activity superior isolates in the greenhouse condition. Definitive identification was performed by 16S rRNA gene sequencing. All three groups had plant growth promoting characteristics. Halophilic, alkaliphilic and haloalkaliphilic strains increased wheat yield about 20.6%, 42.7% and 58.2% in comparison with the control, respectively. The economic grain yield was maximum in H7 (3366 Kg ha-1), A11 (5530 Kg ha-1) and HA6 (2672 Kg ha-1) strains. The 16S rRNA gene sequencing indicated that all of them were owned to Bacillaceae family. These bacteria belonged to four genera including, Alkalibacillus, Bacillus, Haloalkalibacillus and Virgibacillus. H1 and H7 belonged to Virgibacillus genera and Virgibacillus pantothenticus species, respectively. Both superior alkaliphilic isolates were classified to Bacillus clausii. The haloalkaliphilic isolates (HA1 and HA6) were allocated to Virgibacillus marismortui and Alkalibacillus haloalkaliphilus species, respectively. All three extremophilic native groups of bacteria had the ability to aid the wheat plant to deal with high stresses, but plants inoculated with haloalkaliphilic strains had higher yield compared to the other groups due to better root growth and development. <![CDATA[<b>Novel hydrocarbonoclastic metal-tolerant <i>Acinetobacter</i> and <i>Pseudomonas</i> strains from Aconcagua river oil-polluted soil</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400017&lng=es&nrm=iso&tlng=es Bioremediation of sites polluted with petroleum hydrocarbons and heavy metals is a major challenge. The aim of this study was the isolation and characterization of hydrocarbon-degrading and heavy metal-tolerant bacteria. Sixteen hydrocarbonoclastic bacteria were isolated by enrichment from a crude oil-contaminated soil at Aconcagua river mouth, central Chile. Most strains were cocci-shaped and exhibited circular cream-colored colonies with smooth texture. Isolates were resistant to bacitracin and penicillin, and two isolates were motile. Isolates were identified by 16S rRNA and rpoD and rpoB genes sequence analyses. Most isolates belonged to Gammaproteobacteria including Acinetobacter radioresistens (4 isolates), Acinetobacter calcoaceticus (1), Pseudomonas stutzeri (2)and Pseudomonas chloritidismutans (1). Seven isolates possessed 97% 16S rRNA gene similarity with A. calcoaceticus ATCC 23055T, suggesting that these probably represent a new Acinetobacter species. One isolate is an Actinobacteria of the Kocuria genus. All isolates were able to grow on crude oil, whereas eleven Acinetobacter and Pseudomonas strains grew on n-hexadecane. Pseudomonas isolates grew on fluorene (DM88 and DM95) and naphthalene (DD74). Acinetobacter isolates grew on fluorene (DD75, DD79 and DM81) and phenanthrene (DM82). Remarkably, most isolates (except DD79) exhibited copper or cadmium tolerance. These novel hydrocarbonoclastic and heavy metal-tolerant Pseudomonas and Acinetobacter strains are potential biocatalysts for bioremediation. <![CDATA[<strong>Plant and microbial-induced changes in P pools in soil amended with straw and inorganic P</strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400018&lng=es&nrm=iso&tlng=es The aim of this study was to determine the effect of soil amendments on P pools and their depletion by plants and microbes. The experiment was divided into two parts. In Part A, barley straw (C/P 255) was added alone or with inorganic P to reduce the C/P ratio to 127 or 25 (straw treatments). In three other treatments, the same amount of P was added as in the straw treatments as inorganic P (fertilizer treatments). The soil was incubated for three weeks. Then (Part B), wheat was grown for five weeks in one set of soils. Barley straw was added to another set to increase microbial growth and incubated moist for three weeks. P pools were measured at the end of Part A and Part B. At the end of Part A all P pools increased with P addition rate. P pools were greater in the fertilizer than the straw treatments except for microbial biomass P (MBP) which was greater in the straw treatments. After wheat growth, HCl-P, phosphatase-P, citrate-P, CaCl2-P were depleted compared to Part A, MBP was higher. Addition of barley straw in Part B induced depletion of HCl-P, and citrate-P, but increased phosphatase-P, CaCl2-P and MBP. It is concluded that the size of the P pools is mainly influenced by P addition rate not form in which P is added. The impact of growing plants on P pools differs from that of microbes stimulated by high C/P straw addition. <![CDATA[<b><i>Alcaligenes faecalis</i></b><b>associated with <i>Mimosa calodendron</i> rizhosphere assist plant survival in arsenic rich soils</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400019&lng=es&nrm=iso&tlng=es The ferruginous rupestrian grasslands (FRG) in the Iron Quadrangle (IQ) are ecosystems characterized by rocky soils with reduced availability of water and nutrients, but high levels of metals. In order to comprehend the interference of microorganisms on the adaptive process of endemic plant Mimosa calodendrum (Fabaceae), bacteria associated with its roots and rhizosphere were isolated. Fourteen isolates were obtained and subsequently grown in the presence of different concentrations of arsenic (As) species. The isolate Mc250, an Alcaligenes faecalis strain, resisted to 10 mM of As (III) and 800 mM of As (V). In the presence of this strain, atomic spectrometer detected a reduction of 55% for As (III) and 72% for As (V) respectively in 10 mM and 500 mM solution. Scanning electron microscopy of this isolate demonstrated morphological modification and EDX spectroscopy revealed the presence of both As species adsorbed on the membrane, justifying the removal observed in the in vitro assays. To validate this potential removal of As in vivo, tomato plants were used as grown model in the presence and absence of A. faecalis in soil previously contaminated with 5 mM of As (III). After 14 days, plants from contaminated soil had their growth improved when compared to untreated control plants. All these results suggest for the first time that plant-associated bacteria from FRG-IQ present potential for soil rhizoremediation and may benefit the adaptive processes of plants in extreme environments including application in recovering degraded areas. <![CDATA[<b>Presence and diversity of arbuscular mycorrhizal fungi in soil regularly irrigated with</b> <b>vinasses</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000400020&lng=es&nrm=iso&tlng=es The application of organic waste products, such as vinasses, to the soil is a common practice in different countries. Vinasses are a residual liquid generated during various processes such as ethanol production and beverages distillation. However, little is known about how the vinasses affect the content and species distribution of arbuscular mycorrhizal fungi (AMF) in soils irrigated with vinasses. The aim of this research was to determine the presence, spore density and taxonomic identification of AMF to assess in vinasses irrigated (VS) and unirrigated soils (CS). Sixteen species were identified in irrigated and unirrigated soils, with a predominance of Acaulospora mellea, A. scrobiculata, Funneliformis geosporum, F. mosseae and Paraglomus occultum. Only Clareidoglomus etunicatum, Septoglomus constrictum, and Racocetra gregaria were found in VS, while A. morrowiae and Scuttelospora reticulate were only found in CS. The AMF abundance, root colonization, richness and biodiversity indices were not affected by vinasses application. It was found that irrigation of soil with vinasses seemed to have only a limited effect on AMF. To our knowledge, this is the first description of the species of AMF present in soil frequently irrigated with vinasse. This study could serve as a base for further investigations into the effect of vinasse on the soil microbial community and crop yields.