Transposon-based analysis of violacein production in Janthinobacterium lividum

Since the early 1990s, massive declines in amphibian populations have been observed on a global scale. One of the major contributing factors to the decimation of Class Amphibia is the pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd), which has been shown to infect over 350 species on all continents except Antarctica. As Bd lacks host specificity and thrives over a broad geographical range, a growing body of research has been dedicated to examining effective management strategies against Bd. Bioaugmentation in particular has risen to the forefront of Bd research, and the bacterial species Janthinobacterium lividum has proven to be a good candidate for remediation. J. lividum is a bacterial symbiote to many amphibians, and has been shown to inhibit Bd via the production of the metabolite violacein. Violacein production by J. lividum is reliant on quorum sensing which, briefly, is the organized, density dependent phenotypic expression by bacteria via cell-cell communication. Here, J. lividum was subject to transposon mutagenesis, and the resulting mutant library was screened for changes in violacein, which were presumably due to alterations of the quorum sensing system. Restriction digestion and T4 ligation allowed the creation of novel plasmids from the mutant genomes. Sequencing these plasmids identified two genes, which are responsible for the synthesis of the RNA chaperone Hfq and the ATP-dependent protease La. These genes have been previously implicated as a major component of the quorum sensing systems in Vibrio cholerae and Pseudomonas aeruginosa, respectively. Identifying these genes not only provides insight into the quorum sensing mechanisms existing in J. lividum, but also contributes to understanding about violacein production in this organism. Both are extremely valuable when considering J. lividum as an effective management strategy for Bd