Cofilin/ ADF proteins are adjoined to the membrane during the phagosome formation. They regulate the polymerization of actin filaments around the Dictostelium phagosome. Nevertheless, these proteins are also involved in the internalization of the parasite Listeria monocytogenes. A cognin-like protein is also recruited to the membrane in the presence of 3-oxo-C12-HSL. This membrane protein intervenes in cell aggregation thanks to its disulfide isomerase activity, which creates temporary covalent links with membrane proteins of the other cells. Some data demonstrate that some sponge-associated bacteria possess proteins with eukaryotic protein-protein interaction domains. The cognin-like protein may intervene in the capture of these bacteria. 3-oxo-C12-HSL seems to stimulate the de novo protein expression as well as the recruitment of proteins involved in the internalization of bacteria and further in the first step of the endocytosis/ phagocytosis process. Indeed, the over-expression of lysosomal VATPase, early recruited to the phagosomes via tubular lysosomes to establish the hostile acidic environment, suggests that 3oxo-C12-HSL promotes the phagocytosis process in the sponge cells. In the same way, the phagocytosis activity is stimulated in response to 3-oxo-C12-HSL in immune cells of higher vertebrates. This increase of activity due to this molecule may correspond to an ancestral mechanism conserved in the evolution. The 3-oxo-C12-HSL effects on the plant M. truncatula also lead to a modification of the expression of cytoskeletal protein such as a tubulin and a cofilin/ADF protein. To conclude, 3-oxo-C12-HSL may participate in the control of the immune and apoptotic S. domuncula systems. This takeover does not presume of the destiny of bacteria in the eukaryotic cells: taking advantage like in pathological contexts or long-lasting installation like in symbiosis. But the sponge may perceive this signal as a molecular evidence of the bacterial presence/density and may then trigger the first steps of bacterial endocytosis and detoxification mechanism in order to control its bacterioflora. Indeed, this mechanism may lead the sponge to react to the multiplication of the inhabiting bacteria in order to regulate the population. This secreted 3-oxo-C12-HSL is the first molecule demonstrating a paracrine inter-kingdom action in the sponge and in a non-pathological context. These results open up a new perspective in the understanding of the mechanism of regulation of sponge/bacterium relationships. Lectins are carbohydrate binding proteins unrelated to immunoglobulins that display no enzymatic activity towards the recognized sugars. They are responsible for deciphering the glyco codes playing a central role in various biological events such as infections and cell communication and growth. The above cited features elect these proteins as useful tools in bioscience and biomedicine.