Rosella Cataldo

Biofilms are key bacterial communities in genetic and adaptive resistance to antibiotics as well as disease control strategies. The mature high-coverage biofilm formations of the Vibrio campbellii strains (wild type BB120 and isogenic derivatives JAF633, KM387, and JMH603) are studied here through the unstraightforward digital processing of morphologically complex images without segmentation or the unrealistic simplifications used to artificially simulate low-density formations. The main results concern the specific mutant- and coverage-dependent short-range orientational correlation as well as the coherent development of biofilm growth pathways over the subdomains of the image. These findings are demonstrated to be unthinkable based only on a visual inspection of the samples or on methods such as Voronoi tessellation or correlation analyses. The presented approach is general, relies on measured rather than simulated low-density formations, and could be employed in the development of a highly efficient screening method for drugs or innovative materials.

Biological matter is attracting increasing attention because it shows innovative features that have found several applications in technology, from highly sensitive sensors for medical treatments to devices for energy harvesting. Furthermore, most of its phenomenology remains unclear, thus giving hints for speculative investigations. In this Letter, we explore the possibility to use a well-known photosensitive protein, the Reaction Center of Rhodobacter sphaeroides, to build up an electrical pH sensor, i.e., a device able to change its resistance depending on the pH of the solution in which it crystalizes. By using a microscopic model previously tested on analog proteins, we investigate the electrical response of the reaction center single protein under different conditions of applied bias, showing the feasibility of the bio-rheostat hypothesis. As a matter of fact, the calculated resistance of this protein grows about 100% when going from a pH = 10 to a pH = 6.5. Moreover, calculations of the current voltage characteristics well agree with available experiments performed with current atomic force microscopy under neutral conditions. All findings are in qualitative agreement with the known role of pH in biochemical activities of reaction center and similar proteins, therefore supporting a proof-of-concept for the development of innovative electron devices based on biomaterials.