## 4 Biofilm  
### Biofilm Formation  
A biofilm is a structured community of microbial cells enclosed in a self-produced extracellular polymeric matrix that are adherent to the a surface, the interface, and each other [145; 146]. Biofilms protect the bacteria and allow them to survive in hostile environmental conditions. Bacterial biofilms can resist the host immune response and are much more resistant to antibiotics and disinfect treatments than planktonic bacterial cells [147]. Biofilm formation occurs in several steps according to a well-established pattern, as shown in Figure 1. First, bacteria adhere to a surface (1) and start to develop an irreversible attachment (2). The bacteria then group together, multiply, and form microcolonies (3). During the biofilm maturation phase, bacteria begin to synthesize extracellular polymeric substances (EPS), which are made up of polysaccharides, proteins, extracellular DNA (eDNA), and lipids. Within hours of accumulation of EPS, bacteria are trapped in a complex protective extracellular matrix (Figure 2), forming a mature biofilm that offers a protective environment against antibacterial agents (4) [148; 149]. The final stage in biofilm formation is the detachment or dispersal of bacterial cells, which can then colonize new surfaces (5) (Figure 1). Thus, these bacterial cells have the ability to adhere to new surfaces and reform a biofilm and can contribute to biological dispersion, which plays an important role in the transmission of bacteria and the spread of cross contamination and infection [111; 150].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Foodborne Pathogen** & **Food Environment Processes** & **Food Equipment Isolation** & **Food Product** & **References** \\ \hline  & & Tomatoes & [143] \\ \hline Individual production & & Poultry food & \\ chains & & Chicken gizzards & [144] \\ \hline
3D food printing & & Food ink capsules & [122] \\ systems & & Bulk tank milk & \\  & Milk filter & Raw milk & [123] \\ \hline  & & Fresh beef & [130] \\ \hline  & Dish cloth & Chicken & [131] \\ Countertop & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: _Cont._  
Figure 1: Different steps of biofilm formation.  
Biofilm resistance is linked to a microbial cell-to-cell communication system called quorum sensing (QS). When a bacterial community reaches a high level, signaling molecules are synthesized. The expression of QS molecules differs biochemically between Gram-negative and Gram-positive cells. In Gram-positive bacteria, the main function of the QS system is to synthesize intracellular molecules called autoinducer peptides (AIPs). However, in Gram-negative bacteria, autoinducer molecules are secreted from parent molecules called N-acyl homoserine lactones (AHLs). These molecules can enter the intracellular environment to regulate gene expression in a manner dependent on the extracellular environment. This ability helps bacteria to survive environmental stressors [151; 152; 153].  
Inhibition of QS or quorum quenching [154] is therefore a preferred strategy to fight against microbial infections. This strategy attenuates the pathogenicity of microbes and increases the sensitivity of microbial biofilms to antibiotics. This happens by degrading the communication molecules involved in quorum-sensing or -blocking receptors for the same molecules [154]. These mechanisms are implemented by certain organisms, such as plants. In this respect, various bioactive molecules, notably terpenoids, flavonoids, and phenolic acids, exhibit numerous anti-QS mechanisms via inhibition of autoinducer release, sequestration of QS-mediated molecules, and deregulation of QS gene expression [151; 155; 156].