Biofilm is a collection of microbes or cells of microorganisms, particularly bacteria of different species that form a community, attached to a surface, and covered by patches of carbohydrates released by the bacteria. Biofilms are formed because microorganisms tend to create a microenvironment and niche (niche) they own. This is because 1). Nutrient limitation and prevent the release of the surface cells. and 2). The presence of quorum sensing (ability to ensure sufficient cell numbers before making a specific biological response).
A biofilm consists of microbial cells (2-5%) of many species, polysaccharides (1-2%), protein (extracellular and result from lysis) (<1%), DNA/RNA (<1%) and interstitial water (95 %). Physico-chemical properties in biofilms are able to form the mechanical stability, binding water molecules, and the formation of a hydrophilic surface. Biofilms and microbial aggregates such as floc (biofloc) are bound together by Extracellular Polymeric Substances (EPS).
EPS mediates cohesion and adhesion power in biofilms on surfaces. These bacteria do not work individually but gather into long chains and begin the biofilm formation stage. Some bacterial species that can form biofilms are E. coli, Salmonella spp., S. aurens, Vibrio spp., Psedomonas spp., and some Bacillus spp.
Biofilm growth stages consisting of: 1). Temporary sticking. 2). Permanent sticking. 3). Maturation I. 4). Maturation II. 5). Dispersion.
Biofilms are resistant to disinfectants and high-temperature compounds for their defense mechanism (extracellular polysaccharide compound). Age colony biofilm resistance comparable to the chemical compound. Weakness biofilm that is able to be inactivated or destroyed with the use of anti-fouling chemicals.
Biofilms have an important role in the ecosystem, that are: 1). Getting involved in nutrient cycles, especially the degradation of organic matter present in the water. 2). Immobilization or accumulation of various pollutants, especially excess nutrient ions. This capability results from the electrically charged material contained in the polymer biofilm. 3). Place the process of gene shuffling (microbial gene pool) that affect the behavior and characteristics of the microbes in aquatic ecosystems – the transfer of genes resistant to antibiotics.
Some of the direction of development of biofilms can be developed in aquaculture, namely: 1). Biological filters. 2). Management of water and wastewater aquaculture. 3). Probiotic (biological control agent).
Source: Kurniawan, Andi. 2019. Biofilms on aquaculture (control and direction of utilization). Brawijaya University. National Symposium on Shrimp Aquaculture Vanamei.