Microbial Biofilms: How Effective in Rhizobium–Legume Symbiosis?

Abstract

Diverse genera of bacteria live as microbial communities called biofilms on biotic or abiotic surfaces, or interfaces. They exhibit elevated microbial action, as a result of symbiosis in biofilm structure and physiological adaptation. The formation of fungal bacterial biofilms by bacterial colonization on biotic fungal surfaces gives the biofilms enhanced microbial effectiveness compared to monocultures. When the bacteria include rhizobia, they are called fungal rhizobial biofilms. The role of biofilm formation in Rhizobium legume N-2-fixing symbiosis contributes to effective root colonization by rhizobia and provides an effective mode for defense and helping rhizobia to survive under harsh and nutrient-limiting environments. Biofilms also indirectly promote the symbiosis by assuring a healthy root system, preserving rhizospheric moisture, and modifying soil pH, leading to enhanced nutrient cycling, biocontrol etc. Poor survival of rhizobial monocultures in inoculant technology can be overcome by using biofilmed inocula called biofilmed biofertilizers (BBs), which could improve legume production. The use of BBs is also likely to develop cooperative symbioses between Rhizobium-legume interaction and microbe microbe interactions in the biofilm, which will make an improved effect on the former, leading to increased legume production.