Combined theoretical and experimental approaches for bacterial aggregation studies towards the improvement of bioremediation processes

Bacterial aggregation process is usually considered as a step prior to adhesion to a surface for the biofilm establishment. However, the formation of clusters that remain in suspension has already been described as a third microbial lifestyle. Pseudomonas extremaustralis 2E-UNGS is a microorganism native to the contaminated Reconquista River, Argentina. This strain is able to aggregate, develop biofilms and biosorb metals, secreting biosurfactants and exopolymeric substances, properties that contribute to its application in the design of sustainable environmental biotechnologies, including bioreactors. The aim of this work was to study the kinetics of P. extremaustralis 2E-UNGS self-aggregation by a combination of experimental, bioinformatic and theoretical modelling approaches to be potentially applied in the design of improved biotreatments, especially of electroplating effluents. The kinetics was studied by bright-field microscopy and FIJI^® for digital analysis. Time-dependent dispersion of cell cluster sizes was obtained. A physical model based on self-assembled 2D micelle dispersions was used to describe the energetic cost of the aggregation process. A low-nutrient concentration culture medium promoted the formation of small and compact cell clusters. The genomic study revealed the presence of pelABCDEFG and pgaABCD operons, involved in exopolymer production and associated with self-aggregation regulation. Contrasting experimental, bioinformatic and numerical results shed light on some of the mechanisms underlying the phenomenon of bacterial aggregation, useful for biotechnological applications.

Modelling bacterial aggregation under different experimental conditions