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Bacteria thrive in a variety of environments in two general forms, as free-floating planktonic cells, or in groups growing in a biofilm. Microbial biofilms form on abiotic and biotic surfaces in aquatic ecosystems, as well in human hosts. The physical structure of a biofilm provides a protective, but also selective barrier, to hostile environmental conditions, allowing bacteria to grow and reproduce protected from heavy metal contamination, acid exposure, or antibiotics. Because of the selective advantage biofilms provide for bacteria living in harsh environmental conditions, whether in the natural environment, or in a host, it is important to understand the structure-function relationship between biofilm structure and how they resist these challenges. The relationship between biofilm structure and quorum sensing has not been studied in Janthinobacterium sp. These species produce violacein, a purple pigment that has anti-microbial, anti-viral, anti-tumoral, and anti-fungal properties, making it a potential tool for bioaugmentation or medical treatment, evident when cells are in a biofilm. In this study, the internal and external biofilm structure of violacein-producing Janthinobacterium sp. strains BJB426 and BJB446 isolated from the Hudson River Valley area were analyzed using confocal laser scanning microscopy and atomic force microscopy. Atomic force microscopy revealed that cells embedded in biofilms from the two wild-type strains differed in morphology, including cell length, width, and surface roughness. AFM quantitative and visual data on biofilm structure can eventually be used to elucidate the regulation of biofilm and violacein production through quorum sensing.
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Zambrano, Alessia Sofia, "Examination of violacein-producing Janthinobacterium species’ biofilm structure" (2016). Senior Projects Spring 2016. 128.