The ability of the fungus Ophiostoma piceae and the bacterium Pseudomonas putida to form mixed biofilms demonstrated

A team of researchers led by Dr. Jorge Barriuso (Centro de Investigaciones Biológicas Margarita Salas-CSIC) shows the ability of the fungus Ophiostoma piceae to constitute biofilms on plastic surfaces, both isolated and in mixed cultures with the bacterium Pseudomonas putida KT2440. The work, recently published in the journal Environmental Microbiology, also characterizes the molecular signals of fungus and bacteria that modulate this process.

Biofilms are collective structures formed by microorganisms adhered to biotic or abiotic surfaces and are covered by a polymeric extracellular matrix made up of exopolysaccharides (EPS), proteins, and nucleic acids. They provide resistance to changes in temperature, pH, availability of nutrients, or exposure to antibiotics, among other factors. Although traditionally associated with bacteria, these structures are also produced by other organisms, such as fungi.

This work demonstrates for the first time the ability of the fungus O. piceae, producer of enzymes with biotechnological applications, to constitute biofilms by themselves or in consortium with the bacterium P. putida, leading to mixed biofilms.

The interkingdom molecular processes of communication are of special relevance in the case of mixed biofilms and Ruíz et al. show that the formation and architecture of these biofilms is influenced by the quorum sensing signal molecules of both the fungus and the bacteria. Furthermore, the use of modified strains has made it possible to characterize the adhesion proteins which are induced, as well as the signal transduction pathways involved in the process.

The results presented in this work have biotechnological implications in the context of the formulation of catalytic biofilms. Additionally, and since there are mixed biofilms analogous to these formed by pathogenic bacteria and fungi, they could also have biomedical applications.

Reference: The architecture of a mixed fungal–bacterial biofilm is modulated by quorum‐sensing signals. Alberto Ruiz, Marta Herráez, Stefanie B. Costa‐Gutierrez, María Antonia Molina‐Henares, María Jesús Martínez, Manuel Espinosa‐Urgel, Jorge Barriuso* (2021) Enviromental microbiology. https://doi.org/10.1111/1462-2920.15444