Sustainable agricultural practices preserve the biodiversity of Burkholderia species in Argentinean soils

DRAGHI, W.O.; DEGROSSI, J.; ABDIAN, P.L.; SOLER BISTUÉ, A.; WALL, L.G.; ZORREGUIETA, A.

Mar del Plata

Congreso; VIII REunión Anual Sociedad Argentina de Microbioligía General; 2012

Sociedad Argentina de Microbiología General

Burkholderia are ubiquitous bacterial species able to occupy a wide range of niches in nature, as soils, water sources, plants and mammalians, and fulfilling diverse functions in their habitats, from beneficial agents to pathogenic behavior against plants or humans. In the context of the BIOSPAS global project, we performed a survey to recognize the actual biodiversity of Burkholderia species presents in agricultural soils, and the influence of different productive management on the diversity status of this bacterial genus. Soils from four sites (Bengolea, Monte Buey, Pergamino) and three treatments (Natural Environment (NA), Sustainable Agricultural Practices (BPA) and Non Sustainable Agricultural Practices (MPA) were obtained during February and September 2011 and 2012. Soils samples from the top 10 cm were taken homogenized and maintained until posterior analysis. To obtain cultivable Burkholderia strains, soils solutions were seeded on PCAT medium and colonies were confirmed as Burkholderia through the presence of specific recA amplicon. Isolates belong to Burkholderia genus (recA +) were sequenced to determinate their specific taxonomic level. The presence of Burkholderia species was highly variable among sites during the different annual season, so a huge number of isolates was necessary to obtain a snapshot of diversity status in the different sites. In this sense, more than 600 Burkholderia strains were isolated and sequenced to reach steadies biodiversity indexes. Seventeen species were recorded, most of them (c.a. 70%) belong to the Burkholderia cepacia Complex (a set of Burkholderia species able to produce infections in mammalians) while the resting isolates were not BCC constituent or did not match with the actual described species, suggesting the existence of undescribed species in our soils. In spite of natural variability between samples according to the season or soil management, an overall analysis showed that NA and BPA presented the highest biodiversity values, according to Shannon Index, while MPA showed lowest indexes values, and a bigger dominance of BCC species, reaching c.a. 80% of the total isolates (mainly B. ambifaria strains). Our approach showed that about 25% of the total Burkholderia species described up to now are inhabitant of Argentinean soils. This population showed to be highly diversity in natural environments, and the use of BPA maintains these levels of diversity. In contraposition, soils under non sustainable agricultural practices are dominated by low diverse Burkholderia population, suggesting that sustainable agricultural practices are key process in keeping soil bacterial biodiversity as well as sustainable and high crop production.