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Specialization is a common feature in animal societies that leads to an improvement in the fitness of the team members and to an increase in the resources obtained by the team. In this paper we propose a simple reinforcement learning approach to specialization in an artificial multi-agent system. The system is composed of homogeneous and non-communicating agents. Because there is no communication, the number of agents in the team can easily scale up. Agents have the same initial functionalities, but they learn to specialize and so cooperate to achieve a complex gathering task efficiently. Simulation experiments show how the multi-agent system specializes appropriately so as to reach optimal (or near-to-optimal) performance in unknown and changing environments.

Microorganisms colonize surfaces and develop biofilms through interactions that are not yet thoroughly understood, with important implications for water and wastewater systems. This study investigated the interactions between N-acyl homoserine lactone (AHL)-producing bacteria, yeasts and protists, and their contribution to biofilm development. Sixty-one bacterial strains were isolated from activated sludge and screened for AHL production, with Aeromonas sp. found to be the dominant AHL producer. Shewanella xiamenensis, Aeromonas allosaccharophila, Acinetobacter junii and Pseudomonas aeruginosa recorded the highest adherence capabilities, with S. xiamenensis being the most effective in surface colonization. Additionally, highly significant interactions (i.e. synergic or antagonistic) were described for dual and multistrain mixtures of bacterial strains (P. aeruginosa, S. xiamenensis, A. junii and Pseudomonas stutzeri), as well as for strongly adherent bacteria co-cultured with yeasts. In this last case, the adhered biomass in co-cultures was lower than the monospecific biofilms of bacteria and yeast, with biofilm observations by microscopy suggesting that bacteria had an antagonist effect on the whole or part of the yeast population. Finally, protist predation by Euplotes sp. and Paramecium sp. on Aeromonas hydrophila biofilms not only failed to reduce biofilm formation, but also recorded unexpected results leading to the development of aggregates of high density and complexity.

E. and Martín-Cereceda, M., (2019). 'Rain-fed granite rock basins accumulate a high diversity of dormant microbial eukaryotes'. Microbial ecology, pp. 1-16.

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