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AHV focuses on applying quorum sensing in relevant solutions. This science explains how bacteria collaborate with each other using signal molecules (see figure 1). They use these molecules to communicate with other bacteria in their environment, and to work together effectively when they reach a critical population point (Bassler et al., 2005).
QUORUM SENSING (QS)
When specific bacteria are present in small numbers, their signal molecules are strongly diluted, making performing actions inefficient (Bassler, 2009).
However, when there is a high population density, the signal molecule concentration becomes so high that they regularly bind to receptors on similar bacterial cells (Bassler, 2009).
This way the group knows that an action or attack can be carried out effectively, and can coordinate accordingly (Reading et al., 2005).
An example of this is the coordination of certain bacteria on the teeth, which allows them to form plaque, or in the body, which is called biofilm.
QS: HOW BACTERIA TALK
Figure 1: Cell communication (AHV International, 2020 – based on Bassler / Keulemans, De Volkskrant, 2017)
1. Bacteria release signal molecules, which land on the receptors of similar bacteria (see magnification). This process is similar to gears that fit together.
2. If more molecules are measured around the bacteria, the behaviour of this group of bacteria changes.
3. They will then, for example, emit light or produce mucus (biofilm).
Figure 2: Growth of a bacterial biofilm on a skin wound, from initial attachment through microcolony formation, signalling and mature biofilm (AHV International, 2020 – based on Legger, 2020)
Although biofilms are very heterogeneous and can vary greatly in composition and structure, there is a characteristic scheme for the sequence of biofilm formation (see figure 2):
After the attachment phases, multiple layers of cells (micro-colony, matrix formation) form to protect themselves against threats from the external environment. In this biofilm, bacteria continue to multiply, despite being in an inactive state, different from the bacteria that live outside the biofilm. As soon as the biofilm is stable (mature), both active and passive diffusion can take place. The biofilm then releases bacteria into the environment in a partially controlled way (i.e. outbreak) (Hall-Stoodley et al., 2005).
DID YOU KNOW? The total surface of an udder can be up to 250 m2 (Swanson et al., 1967).
SUPPORT THE IMMUNE SYSTEM
The immune system’s ability to effectively do its job is of vital importance to your animal’s health (Keulemans /Bassler, 2017). However, some bacteria can create a protective mucus layer (biofilm) that envelops an entire bacterial community (KU Leuven, 2020).
Inside this biofilm, these bacteria are difficult to detect by, for example, immune cells of your animal. Quorum sensing is one of the factors responsible for this (Parsek et al., 2005).
Progressive Dairy magazine (2011) gives an insight in the difference between a healthy udder (1) and an udder with biofilm (2). Using dye the biofilm is made visible.
1. Dissection of a healthy udder.
2. Dissection of an udder with biofilm, indicated using dye (green).