Tactic Responses of Bacteria to Pollutants: Implications for the Degradation Efficiency of Microbial Biofilms

Abstract

In nature, microorganisms are mostly found attached to surfaces forming biofilm communities. The study of these biofilms is primarily focused on basic research to better understand their multicellular way of life, and negative implications for clinical cases and industrial processes. However, there is good reason to increase our knowledge regarding how to stimulate biofilm formation by bacteria, and particularly to exploit these biofilms for their efficient bioremediation of the wide spectrum of the environmental pollutants. Biofilm establishment and maintenance relies on a complex interaction of different mechanisms since bacterial movement and attachment is mediated by swimming, swarming and twitching motility, quorum sensing mechanisms, biosurfactant secretion and the presence of the chemotactic responses. These chemotactic responses include reactions to inorganic species and xenobiotics that are commonly present in polluted aquatic or soil environments as a result of industrial processes. Microorganisms that display positive chemotactic responses are able to swim towards an adsorbed chemical and, following biofilm formation, can increase pollutant bioavailability by surfactant synthesis, further impacting the rate and extent of pollutant degradation or transformation. The manipulation of biofilm condition and chemotactic response may be manipulated in ex bioreactors to improve the bioremediation efficacy of a wide range of pollutants, and particularly for the treatment of metal contaminated media.