Project description:Photobacterium leiognathi is a bioluminescent symbiont of fish of the Leiognathidae family. Here, we present the full-genome sequence of P. leiognathi strain JS01, a strain isolated from a nonluminescent Loligo sp. squid of Singaporean origin. No finished genome sequence of this species is currently publicly available.
Project description:UnlabelledBacterial bioluminescence is taxonomically restricted to certain proteobacteria, many of which belong to the Vibrionaceae. In the most well-studied cases, pheromone signaling plays a key role in regulation of light production. However, previous reports have indicated that certain Photobacterium strains do not use this regulatory method for controlling luminescence. In this study, we combined genome sequencing with genetic approaches to characterize the regulation of luminescence in Photobacterium leiognathi strain KNH6, an extremely bright isolate. Using transposon mutagenesis and screening for decreased luminescence, we identified insertions in genes encoding components necessary for the luciferase reaction (lux, lum, and rib operons) as well as in nine other loci. These additional loci encode gene products predicted to be involved in the tricarboxylic acid (TCA) cycle, DNA and RNA metabolism, transcriptional regulation, and the synthesis of cytochrome c, peptidoglycan, and fatty acids. The mutagenesis screen did not identify any mutants with disruptions of predicted pheromone-related loci. Using targeted gene insertional disruptions, we demonstrate that under the growth conditions tested, luminescence levels do not appear to be controlled through canonical pheromone signaling systems in this strain.ImportanceDespite the long-standing interest in luminous bacteria, outside a few model organisms, little is known about the regulation and function of luminescence. Light-producing marine bacteria are widely distributed and have diverse lifestyles, suggesting that the control and significance of luminescence may be similarly diverse. In this study, we apply genetic tools to the study of regulation of light production in the extremely bright isolate Photobacterium leiognathi KNH6. Our results suggest an unusual lack of canonical pheromone-mediated control of luminescence and contribute to a better understanding of alternative strategies for regulation of a key bacterial behavior. These experiments lay the groundwork for further study of the regulation and role of bioluminescence in P. leiognathi.
Project description:Genomic DNA extracted from two different Photobacterium profundum strains: SS9 strain (completely sequenced and used to made the microarray) and DSJ4 strain were labeled with Cy3 and Cy5 fluorophores and competitively hybridized on the microarray built on the basis of the SS9 strain genomic sequence. Aim: the identification of the genomic regions absent in the DSJ4 strain with respect to the SS9 strain. The SS9 strain was isolated from the Sulu Trench and display an optimum growth at 28 MPa (2800 metres of depth). The DSJ4 strain was recovered from a sediment sample obtained from the Ryukyu Trench (Japan) at a depth of 5110 m and displays an optimum growth at 10 MPa (but shows no significant change in growth at pressure up to 50 MPa).