Bacterial biofilm production and water stress resistance by rhizobacteria associated to sugarcane (Saccharum officinarum) Linnaeus (POACEAE)

Abstract

The water restriction is a limiting factor in agricultural production. Some rhizobacteria, to live in symbiosis with the plant, can benefit plant growth. Among the skills of micro-organisms is the ability to survive in extreme environments, such as water stress, as well as having the biofilm production ability. The objective of this study was to evaluate the potential of four bacterial isolates from sugarcane rhizosphere as resistance to water restriction and biofilm production. A qualitative and other quantitative assay to produce biofilm was conducted. The qualitative assay was based on colorimetry with crystal violet. The qualitative test was developed by the violet colorimetric ratio of technical and optical density at 540 nm. Bacterial growth testing in low water activity was developed by inoculating the bacterial isolates in the TSA culture medium (10%) supplemented with sorbitol (405 gL-1) at 28 °C, yielding the corresponding Aw value 0.919. All strains were able to produce biofilms in both tests however isolated Bacillus subtilis was most effective, with the greatest biofilm production ratio. All isolates were also skilled in the growing culture medium with low water activity.
 KEYWORDS: plant protection, rhizobacteria, plant gowth promotion, symbiosis.