Chapter 15 - Recent advances in biofilm formation and their role in environmental protection

Abstract

Biofilms are heavy growths of microorganisms that aggregate to form colonies, which further attach to the surface consisting of a slime layer for protection and survival of the microbial cell. Biofilms, produced by both gram-positive and gram-negative bacteria, are found in almost all environments (biotic and abiotic), and have a range of environmental applications (Arnaouteli, Bamford, Stanley-Wall, & Kovács, 2021; Li, Li, Wang, & Wang, 2010; Manickam, Misra, & Mayilraj, 2007). Biofilm is developed through the production of an extracellular matrix, which is mainly composed of sticky extracellular polysaccharides (EPS) and proteins produced by the microbial cell (Branda, Vik, Friedman, & Kolter, 2005). The biofilm formation occurs through a series of events: adhesion of individual microbial cells to a surface area, cell proliferation and aggregation into micro-colonies, extracellular matrix production, and cell detachment (Fig. 15.1), (Arnaouteli et al., 2021). Environmental pollution is also increasing rapidly with the increase in environmental pollutants, viz., hydrocarbons, polyethylene heavy metals, and industrial waste, along with the human population (Puhakka et al. 1995; Song, 2009; Yong & Zhong, 2013). The presence of these toxic pollutants in the environment can affect ecosystems and ultimately human health. Biofilm-associated bacteria play an important role in protecting the environment from such threats (Ferrer, Golyshin, & Timmis, 2003; Hunter, Ekunwe, Dodor, Hwang, & Ekunwe, 2005; Kang & Park, 2010; Malik & Grohmann, 2012). Many biofilm-forming bacterial species potentially provide a suitable microenvironment for efficient bioremediation processes to naturally and artificially overcome these environmental constraints (Huang et al. 2013). Aquatic contaminants are generally characterized by their toxicity to living organisms and the environment. Biofilm-mediated wastewater and sewage treatment processes in industries are the most efficient techniques because of their distinct advantages over conventional methods (Rinaudi et al. 2006). Moreover, bacteria physically interact with the surface of the plant root system and further stabilize the plant-associated habitat. Hence rhizobia biofilms act as an economically important root colonizer, fixing atmospheric nitrogen into ammonia (Crueger, Crueger, Brock, & Brock, 1990). Therefore, the present chapter deals with the events involved in biofilm formation, the important role of biofilms in environmental protection, and the role of biofilm formation for health. Various bacteria and their role in environmental protection have been depicted in Table 15.1.