CONICET | Buscador de Institutos y Recursos Humanos

Biofilms are recognized as the predominant form of bacterial growth in the environment. Growth in a biofilm provides many advantages for bacteria, including enhanced resistance to environmental stresses, such as desiccation and anti-microbial agents, as well as to host defenses. Biofilms can be defined as structured communities of sessile microbial aggregates, enclosed in a self-produced polymeric matrix, attached to an abiotic or biotic surface. The root surface is an example of biotic surface in which many microorganisms form biofilms for the establishment of an effective plant?microbe interaction. Colonization of plant root surface by Plant Growth Promoting Bacteria (PGPB) has been associated with their capacity of biofilm formation. PGPB are a group of microorganisms able to confer beneficial effects on plant growth and development, applied as an alternative or a supplemental way of reducing the use of chemicals in agriculture. After inoculation process they have to colonize the root. The initial phase of colonization is the bacterial attachment to the root surface followed by a growth forming microcolonies or biofilms, and some of them are able to enter roots and establish endophytic populations. In the present work some common batch systems were carried out in different culture media to evaluate the ability of Burkholderia tropica Mto-293 to form biofilm on abiotic surfaces. This bacterium is an endophytic nonpathogenic plant-associated Burkholderia specie belonging to the group of PGPB with potential and safe application in an agricultural context. Biofilm studies were carried out using multiwell plates and glass tubes and the biofilm formation was monitored by crystal violet stain. The architecture of biofilm was analyzed on glass slides by fluorescent microscopy (FM) and confocal laser scanning microscopy (CLSM) using a derivative strain of B. tropica with the gfp marked gene. B. tropica was able to attach to both types of surfaces (polypropylene and glass) and developed a biofilm on the air-liquid interphase but not for all culture media tested. The biofilm was observed in the media with ammonia as Nitrogen source in multiwell plates but in glass tubes the best media were those with yeast extract and glycerol, where the polysaccharide production was also observed. Biofilm formation of B. tropica was evaluated over time (24, 48, and 72 h) by FM showing sequential microbial aggregates of cells immersed in a dense matrix on the air-liquid interphase. By CLSM it was possible to determine 3D architectural characteristics of the mature biofilms formed by B. tropica.