Microbial aggregation in low viscosity media: experiments and modelling

GOTTING, ANDREA; DANIEL, MARÍA ALEJANDRA; CARUSELA, MARÍA FLORENCIA; VULLO, DIANA; BERAHA NATALIA

Coyhaique

Conferencia; Conference Physics of Active Matter 2022; 2022

Universidad de Chile

Pseudomonas extremaustralis 2E (former P. veronii 2E) is a native microorganism from the highly contaminated Reconquista River, Buenos Aires, 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. The objectives of this work were to understand the kinetics of P. extremaustralis 2E aggregate formation under different growing conditions by image capture and to model and numerically study the bacterial behaviour through the use of an own-designed code. As these clusters were previously observed in complex culture media, the temperature and carbon source effects were evaluated along 24 h. Growth parameters were recorded monitoring optical density, pH and cell dry weight. Kinetics of aggregate formation was studied by applying brightfield microscopy capturing 2D images then analyzed with the FIJI\®-Analyze Particles. A dispersion of cellular aggregates was obtained as a time function, by processing their area, width and height. In this first approach, the nature and increment of carbon source promoted the formation of cellular aggregates for P. extremaustralis 2E. The development and behaviour of the bacterial clustering was also analyzed from a theoretical approach. The evolution of the cell aggregation under the assayed experimental conditions were numerically studied considering a aggregation-fragmentation model that couples the dynamics of bacterial clusters with the nutrient's availability. Contrasting the experimental and numerical results shed light on some of the mechanisms underlying the phenomenon of bacterial aggregation.