Many biofilm-specific phenotypes are controlled by ""quorum sensing."" this system allows bacteria to regulate gene expression according to the concentration

Many biofilm-specific phenotypes are controlled by "quorum sensing." This system allows bacteria to regulate gene expression according to the concentration of bacteria.

Explanation:

Quorum sensing is basically a process which depends upon the density dependent communication of bacteria. Higher the number of bacteria, more will be the communication. Example of quorum sensing is biofilms which grow on various surfaces.

Some auto-inducers like peptides and N-acyl homoserine lactone are produced by bacteria during this process which in turn activate some transcription factors to cause gene expression.

In bacteria, it mainly serves the purpose of bioluminescence, sporulation and nitrogen fixation.

substitution is the answer in this case

because they are eaten by the frog and the frog getseaten by the snake and the snake by the eagle