Fig. 3.

Scheme of horizontal gene transfer by mating pair formation of bacteria in a planktonic environment: a bacterium that harbors a conjugative plasmid, called ’donor’, couples through its pilus to another bacterium that will receive the plasmid, called ’recipient’. When a copy of the plasmid was successfully transferred, the recipient finally becomes a new donor, called transconjugant. $V_b$ denotes the velocity at which bacteria swim in a planktonic environment, either before ($V_{b_1}$) or after a tumble event ($V_{b_2}$) (for a short time) by which bacteria change their movement direction. In a biofilm, local interactions occur without further motion of individual cells (colored patches/pixel). This can create spatial patterns that in turn affect how and which bacteria interact with each other. The pseudocode gives an example for a conjugation submodel that considers sensing, adaptation and stochastic local interactions of individual cells. This may also be applied to conjugation in plankton, when only mixing but not swimming of individual cells is considered.