# Electrochemical Control of Biofilm Formation and Approaches to Biofilm Removal
## 2 Biofilms
### Bacteria Forming Biofilms  
It is now understood that approximately 40-80% of bacterial cells on Earth can form biofilms [9]. The formation of biofilms was detrimental in several situations [6; 10; 11]. It is generally believed that biofilm matures after 24 h, forming a thick layer of biomolecules [12]. For example, in food industries, pathogenic bacteria are capable of forming biofilms inside processing facilities, leading to spoilage of foods and endangering the consumer's health [13; 14]. Bacteria are able to colonize and form biofilms on almost all kinds of surfaces, including natural and synthetic surfaces. Biofilms are responsible for chronic illnesses and nosocomial infections, industrial pipe fouling, spoilage of foods, contamination of sea food and dairy products, as well as ship hull fouling. Some of the biofilm-forming pathogenic and potentially pathogenic microbes include _Aeromonas hydrophilia_, _Burkholderia cepacia_, _Enterococcus faecalis_, _Escherichia coli_, _Haemophilus influenzae_, _Klebsiella pneumoniae_, _Listeria monocytogenes_, _Pseudomonas aeruginosa_, _Pseudomonas pseudomallei_, _Proteus mirabilis_, _Staphylococcus aureus_, _Staphylococcus epidermidis_, _Streptococcus pneumoniae_, _Streptococcus pyogenes_, _Streptococcus mutans_, _Streptococcus viridans_, _other _Streptococcus_ species, _Vibrio cholerae_, _Vibrio parahaemolyticus_, and _Candida albicans_[15; 16; 17; 18; 19; 20; 21]. Further biofilm forming microbes include _Bacillus subtilis_, _Bacillus cereus_), _Lactobacillus plantarum_, _Lactococcus lactis_, and _Lactobacillus rhamnus_[15]. There are a few pieces of evidence provided on biofilm-forming fungal species, and in recent years, some genera of pathogenic fungi have been gaining attention and are correlated with biofilm formation [16]. In most conditions, bacteria will generally grow on surfaces in competition with other microorganisms in a mixed species of biofilm [15]. Therefore, the harmful effects of biofilms on human society are manifold. The most common biofilm-forming foodborne pathogens and spoilage organisms are introduced in Table 1[3]. The main stages of bacterial biofilm formation can include the following: adsorption, adhesion, formation of microcolonies, maturation, and dispersal. In general, these stages apply for both bacterial and yeast biofilms [22]. \begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Foodborne Bacteria** & **Growing Substrate** & **Spoiled Food** & **Genes Related to Biofilm Formation** & **References** \\ \hline \multirow{4}{*}{_Bacillus_ (_Bacillus cereus_)} & Stainless steel, plastic, soil, and glass wool & Stributed seeds, fruit juices, fried rice, pasta dishes, meat products, vegetables, and milk products & _tasA_, _galE_, _eps2_, _mogR_, _comER_, _pplcR_, _rpoN_, _codY_, _spo0A_, _abrB_, _sint_, _sinR_ and others & [23; 24; 25; 26; 27] \\ \hline \multirow{2}{*}{_Clostridium_} & \multirow{2}{*}{Multi-species biofilm} & Dairy products, fish, cattle meat, poultry, vegetables, honey, and canned food & _luxS_, _spo0A_, _pilC_, _pilT_, and others & [27; 28; 29; 30] \\ \hline \multirow{4}{*}{_Cronobacter_ spp.}