Biofilms and Light Signaling in Synechocystis sp. Strain PCC 6803

Abstract

Biofilms are how bacteria naturally exist‐enclosed in an extracellular matrix of proteins, nucleic acids, and polysaccharides. This state protects bacteria against environmental stresses, such as antibiotics and biocides. Two strains of Synechocystis sp. Strain 6803, a wildtype strain and an extremely motile mutant strain, were grown in flow cells under identical conditions and their biofilms analyzed using confocal microscopy. A significant difference was found in terms of their biofilm structures and growth. Wildtype biofilms were significantly lower in height compared to the motile strain, and formed uniform biofilms as opposed to dense clusters. We also explored the ability of the motile mutant to move towards light, known as positive phototaxis. Both positive and negative phototaxis have been found in cyanobacteria in response to light signaling. Motile cyanobacteria move via twitching motility, which has been traced to surface appendages known as Type IV pili (Mattick, J. 2002). Our goal was to find the physical conditions required for maximal positive phototaxis and to determine the wavelength of light that induces it. We have found that the motile strain moves at a greater rate under incandescent than fluorescent conditions, and are trying to identify the specific wavelength to which the cyanobacteria respond. This research is supported by the Wellesley College Biological Sciences Department.