Biofilm growth at pore scale in laminar flow

Natural soils are home to an enormous variety of microorganisms. Microbial transport is important for a wide range of natural and artificial processes. However, the transport and distribution of bacteria in water flow at porous scale is still to be fully understood.

The Biofilm is a collective structure of microorganisms and it is covered by a protective layer secreted by the microorganisms themselves. The objective of this study is to identify and characterize the Elemental Biofilm Architectures that develop in a porous medium crossed by a laminar flow. This is a process that frequently occurs in nature, when there is water flow through the soil.

In the case of this study, different flow velocities and the percentage of nutrients (% LB Broth diluted in water) were tested, as well as oxygen control. A non-flagellated fluorescent mutant bacterium of P.Putida was used to analyze bacterial and biofilm growth through a homogeneous porous medium. Also, two different methodologies were carried out during the experiments: Methodology A and B. With methodology A the bacteria were initially grown in the porous media, and then and bacterial free flow was injected at a constant flow rate. In methodology B, the porous media was initially free of bacteria, and a bacterial solution was injected at a constant flow rate during the experiment.

In the experiments, the results show different architectural formations such as streamers, chains, ripples and fine lines. With both methodologies, bacteria develop similar biofilm architectures, such as streamers and ripples; but distributed differently throughout the porous media. The biggest difference relies on the deposit profile: in Methodology A most of the biomass accumulates towards the outlet of the porous media, while for Methodology B towards the inlet.