Some microbes secrete small molecules that induce other microbes to settle nearby. When a certain number of individuals have assembled, the chemical signal is strong enough to induce the aggregation to respond collectively to stimuli. This process is called .

The question is incomplete as it does not have the options which are:

A. bioremediation

B. mutualism

C. quorum sensing

D. quorum settling

E. mass-settling

C. quorum sensing

Explanation:

Quorum sensing is the gene regulation mechanism used by the bacteria to communicate with the other bacteria.  The quorum sensing process depends on the number of bacterial cells or the density of the cells.

When the bacterial number increase in number then the bacterial cells send the signal to the nearby cells and and regulates the expression of the gene.  In the given question, the same chemical signal process depends on the density of the cell and thus quorum sensing is correct.