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Summary Interkingdom communication is of particular relevance in polymicrobial biofilms. In this work, the ability of the fungus Ophiostoma piceae to form biofilms individually and in consortium with the bacterium Pseudomonas putida, as well as the effect of fungal and bacterial signal molecules on the architecture of the biofilms was evaluated. Pseudomonas putida KT2440 is able to form biofilms through the secretion of exopolysaccharides and two large extracellular adhesion proteins, LapA and LapF. It has two intercellular signalling systems, one mediated by dodecanoic acid and an orphan LuxR receptor that could participate in the response to AHL‐type quorum sensing molecules (QSMs). Furthermore, the dimorphic fungus O. piceae uses farnesol as QSM to control its yeast to hyphae morphological transition. Results show for the first time the ability of this fungus to form biofilms alone and in mixed cultures with the bacterium. Biofilms were induced by bacterial and fungal QSMs. The essential role of LapA‐LapF proteins in the architecture of biofilms was corroborated, LapA was induced by farnesol and dodecanol, while LapF by 3‐oxo‐C6‐HSL and 3‐oxo‐C12‐HSL. Our results indicate that fungal signals can induce a transient rise in the levels of the secondary messenger c‐di‐GMP, which control biofilm formation and architecture.

A theoretical discussion is given of some of the energy factors associated with single vacancies in an otherwise perfect graphite lattice, caused by neutron bombardment. First, the loss of r-electron energy is shown to be 2.76 + 0.05 β where β is the molecular-orbital resonance integral for a carbon-carbon bond. Secondly, a careful account is provided of the symmetries of the various electronic states that are possible if it is supposed that the three electrons of the atoms adjacent to the vacancy are allowed to interact and form a pseudo-molecule. The energies of these states are calculated, taking account of configuration interaction. It is shown that the lowest state for a neutral vacancy would be a doubly-degenerate state of symmetry 2 E' . This would lead to a Jahn -Teller equilibrium deformation. Such deformation would not be expected to be large, or to modify the numerical results to any great extent. Finally, the earlier numerical values are combined with the experimental heat of atomization of graphite, and lead to a value for the heat of formation of a vacancy equal to about 10.7 eV. This differs considerably from the observed value, which is of the order of 3.4 eV. It is concluded that the model of a vacancy used may possibly not be correct, and an alternative suggestion is put forward.