INBA   12521
INSTITUTO DE INVESTIGACIONES EN BIOCIENCIAS AGRICOLAS Y AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Novel microalgae-bacterial associations idetified by long term enrichement show striking similarities to plant-bacteria interactions
Autor/es:
DO NASCIMENTO M; CURATTI L
Lugar:
Mar del Plata
Reunión:
Congreso; VIII Congreso de Microbiologia General; 2012
Institución organizadora:
Sociedad Argentina de Microbiologia General
Resumen:
During the last few years crop-based biofuels have emerged rapidly in the global marked as an alternative to fossil fuels. However, warnings on the sustainability and expansion capacity of this industry were raised, especially in relation to competitiveness with the food production industry, extensive land use change and unsustainable demand of agrochemicals. Thus, research and development of rhizosferic microorganismos-based products is gaining interest as a sustainable alternative for the gradual replacement of agrochemicals in modern agriculture.On the other hand, microlagae-based next generation biofuels have attracted much attention lately since they have the potential to ameliorate much of the drawbacks of crop-based biofuels. In contrast to crops, research on the microbial community associated to cultured microalgae is almost non-existent. Recent studies from our laboratory and others show that common plant growth promoting bacteria such us Azotobacter sp. or Azospririllum sp. might be also beneficial to microalgae.  Beyond the technological significance, the fact that these bacteria are seldom found in association with microlgae in nature precludes investigation of the natural basis of bacteria-microalgae associations.This study shows the results of a long term enrichment of associations between bacteria and microalgae. More than fifty different fresh water samples were subcultivated by 1:20 to 1:50 dilution in fresh medium every other fifteen days for two- to three-years. More than thirty monoalgal isolated were obtained, many of them in an axenic form. In parallel, an artificial medium mimicking microalgae photosynthetic exudates was developed for the isolation of bacterial strains that could not be removed out of the microalgae cultures by exhaustive dilution. The isolates were initially classified according to the colony morphology and cell shape. A functional screening was set up in which dilutions of the bacterial cultures were mixed with dilutions of axenic cultures of diverse microalgae from our collection and spotted onto solid medium. These experiments allowed a rapid identification of isolates that presented either a positive or negative effect on microalgae growth. Strikingly, ribotypification by sequencing of the 16S RNA led us to identify some of the most reactive isolates as Herbaspirillum sp., Rhizobium sp.,Bradirryzobium sp., Xanthomonas sp. and Mycobacterium sp., suggesting a common trend of these bacteria to engage in beneficial or pathogenic interactions in either plants or microalgae. The potential significance of these findings is going to be discussing in relation to possibilities for sustainable algae biotechnology and as a model for plant-microbe interactions. ANPCyT.