José A. Siles

Microbial diversity of a Mediterranean soil and its changes after biotransformed dry olive residue amendment.

The Mediterranean basin has been identified as a biodiversity hotspot, about whose soil microbial diversity little is known. Intensive land use and aggressive management practices are degrading the soil, with a consequent loss of fertility. The use of organic amendments such as dry olive residue (DOR), a waste produced by a two-phase olive-oil extraction system, has been proposed as an effective way to improve soil properties. However, before its application to soil, DOR needs a pre-treatment, such as by a ligninolytic fungal transformation, e.g. Coriolopsis floccosa. The present study aimed to describe the bacterial and fungal diversity in a Mediterranean soil and to assess the impact of raw DOR (DOR) and C. floccosa-transformed DOR (CORDOR) on function and phylogeny of soil microbial communities after 0, 30 and 60 days. Pyrosequencing of the 16S rRNA gene demonstrated that bacterial diversity was dominated by the phyla Proteobacteria, Acidobacteria, and Actinobacteria, while 28S-rRNA gene data revealed that Ascomycota and Basidiomycota accounted for the majority of phyla in the fungal community. A Biolog EcoPlate experiment showed that DOR and CORDOR amendments decreased functional diversity and altered microbial functional structures. These changes in soil functionality occurred in parallel with those in phylogenetic bacterial and fungal community structures. Some bacterial and fungal groups increased while others decreased depending on the relative abundance of beneficial and toxic substances incorporated with each amendment. In general, DOR was observed to be more disruptive than CORDOR.

Short-term dynamics of culturable bacteria in a soil amended with biotransformed dry olive residue

Dry olive residue (DOR) transformation by wood decomposing basidiomycetes (e.g. Coriolopsis floccosa) is a possible strategy for eliminating the liabilities related to the use of olive oil industry waste as an organic soil amendment. The effects of organic fertilization with DOR on the culturable soil microbiota are largely unknown. Therefore, the objectives of this study were to measure the short-term effects of DOR and C. floccosa-transformed DOR on the culturable bacterial soil community, while at the same time documenting the bacterial diversity of an agronomic soil in the southeastern Iberian Peninsula. The control soil was compared with the same soil treated with DOR and with C. floccosa-transformed DOR for 0, 30 and 60 days. Impact was measured from total viable cells and CFU counts, as well as the isolation and characterization of 900 strains by fatty acid methyl ester profiles and 16S rRNA partial sequencing. The bacterial diversity was distributed between Actinobacteria, Alphaproteobacteria, Gammaproteobacteria, Betaproteobacteria, Bacilli, Sphingobacteria and Cytophagia. Analysis of the treatments and controls demonstrated that soil amendment with untransformed DOR produced important changes in bacterial density and diversity. However, when C. floccosa-transformed DOR was applied, bacterial proliferation was observed but bacterial diversity was less affected, and the distribution of microorganisms was more similar to the unamended soil.

Effects of Dry Olive Residue Transformed by Coriolopsis floccosa (Polyporaceae) on the Distribution and Dynamic of a Culturable Fungal Soil Community

Dry olive residue (DOR) is an abundant waste product resulting from a two-phase olive oil extraction system. Due to its high organic and mineral content, this material has been proposed as an organic soil amendment; however, it presents phytotoxic and microtoxic properties. Thus, a pretreatment is necessary before its application to soil. Among the strategies for the bioremediation of DOR is treatment with ligninolytic fungi, e.g. Coriolopsis floccosa. This work aimed to assess the diversity of culturable fungi in a soil of the southeast Iberian Peninsula and to evaluate the short-term impact of untransformed and C. floccosa-transformed DOR on soil mycobiota. A total of 1,733 strains were isolated by the particle filtration method and were grouped among 109 different species using morphological and molecular methods. The majority of isolates were ascomycetes and were concentrated among three orders: Hypocreales, Eurotiales and Capnodiales. The soil amendment with untransformed DOR was associated with a depression in fungal diversity at 30 days and changes in the proportions of the major species. However, when C. floccosa-transformed DOR was applied to the soil, changes in fungal diversity were less evident, and species composition was similar to unamended soil.

Biodiversity and chemotaxonomy of Preussia isolates from the Iberian Peninsula

This work documents 32 new Preussia isolates from the Iberian Peninsula, including endophytic and saprobic strains. The morphological study of the teleomorphs and anamorphs was combined with a molecular phylogenetic analysis based on sequences of the ribosomal rDNA gene cluster and chemotaxonomic studies based on liquid chromatography coupled to electrospray mass spectrometry. Sixteen natural compounds were identified. On the basis of combined analyses, 11 chemotypes are inferred.

Effect of DOR Incubated with Saprobe Fungi on Hydrolytic Enzymes Activities and Chemical Properties of Rhizospheric Soil of Lettuce

The dry olive residue (DOR), a by-product of the olive mill industry, is produce in large quantities in Mediterranean countries. The phytotoxic and antimicrobial properties of this residue adversely impact on soil qualities. The objective of this study was to investigate the evolution of soil enzymes activities (acid phosphatase, β-glucosidase, protease and urease) and chemical properties (pH, phenols, total organic carbon (TOC) and soluble carbohydrates) after the agronomic application on lettuce of either un-treated DOR or DOR incubated with inmobilized Panus tigrinus or Fusarium lateritium. A decrease of total phenols and phytotoxicity on lettuce plants in presence of treated DOR related to the un-treated residue was detected. We observed a decrease of all hydrolytic enzymes, except protease, after the soil incubation with un-treated DOR for 15 days. It appears that the high concentration of phenolics compounds inhibited the activities of these enzymes. However, the microbial activity was stimulated by the addition of DOR incubated with the saprobe fungi as indicated by the increase of soil enzyme activities detected. The protease activity was always higher than the control soil irrespective of the type of amendant. The TOC and phenols of rhizospheric soil of lettuce increased after 15 and 30 days of agronomic application of untreated or treated residue and a general decrease of the soluble carbohydrates contents was found after 30 days of soil incubation. The DOR detoxified by saprobe fungi has been seen to have a positive effect to restore the loss rhizospheric soil functionality detected after the addition of un-treated residue.