A multiscale study of bacterial proliferation modes within novel E. coli@Si(HIPE) hybrid macrocellular living foams

For the first time the study at various length scales of E. coli proliferation modes within Si(HIPE) inorganic macrocellular foams is proposed. Both qualitatively and semi-quantitatively, bacterial proliferation within the foam is not homogeneous and is directly linked to the random distribution of Si(HIPE) macroscopic cells. When inoculated in a nutrient loaded Si(HIPE), the bacterial growth is enhanced within the Si(HIPE) matrices compared to the surrounding LB media. The bacterial growth kinetics tends to be faster and the concentration at saturation is roughly 100% times higher. In the case of a Si(HIPE) host free of nutrients, bacterial motion occurs as an infiltration wave; the peak of this propagation wave moves at a constant speed of 88 μm h^-1, while bacterial concentrations within the Si(HIPE) host reach levels far above the ones reached in the presence of nutrients, suggesting a real synergetic relationship between the bacterial colony guests and the Si(HIPE) host. When a nutrient reservoir is present at the opposite position from which bacteria were inoculated, bacterial proliferation is associated with a coalescence process between the growing colonies that were rapidly established within the first hours. When the Si(HIPE) host was fully colonized we found out a specific distance between adjacent colonies of 5 and 15 μm in good correspondence with the repartition of the wall to wall distances of the Si(HIPE) macroscopic cells, meaning that bacterial repartition once colonization occurs is optimum. These results show that Si(HIPE) foams are outstanding candidates for strengthened bacterial proliferation without motion restriction imposed by conventional silica gels.