Nonbioluminescent Strains ofPhotobacterium phosphoreumProduce the Cell-to-Cell Communication SignalN-(3-Hydroxyoctanoyl)homoserine Lactone

Abstract

Bioluminescence is a common phenotype in marine bacteria, such as Vibrio and Photobacterium species, and can be quorum regulated by N-acylated homoserine lactones (AHLs). We extracted a molecule that induced a bacterial AHL monitor (Agrobacterium tumefaciens NT1 [pZLR4]) from packed cod fillets, which spoil due to growth of Photobacterium phosphoreum. Interestingly, AHLs were produced by 13 nonbioluminescent strains of P. phosphoreum isolated from the product. Of 177 strains of P. phosphoreum (including 18 isolates from this study), none of 74 bioluminescent strains elicited a reaction in the AHL monitor, whereas 48 of 103 nonbioluminescent strains did produce AHLs. AHLs were also detected in Aeromonas spp., but not in Shewanella strains. Thin-layer chromatographic profiles of cod extracts and P. phosphoreum culture supernatants identified a molecule similar in relative mobility (R f value) and shape to N-(3-hydroxyoctanoyl)homoserine lactone, and the presence of this molecule in culture supernatants from a nonbioluminescent strain of P. phosphoreum was confirmed by high-performance liquid chromatography-positive electrospray high-resolution mass spectrometry. Bioluminescence (in a non-AHL-producing strain of P. phosphoreum) was strongly up-regulated during growth, whereas AHL production in a nonbioluminescent strain of P. phosphoreum appeared constitutive. AHLs apparently did not influence bioluminescence, as the addition of neither synthetic AHLs nor supernatants delayed or reduced this phenotype in luminescent strains of P. phosphoreum. The phenotypes of nonbioluminescent P. phosphoreum strains regulated by AHLs remains to be elucidated.Photobacterium phosphoreum is a marine psychrotolerant bacterium commonly found free living in temperate waters or in high cell densities in fish gastrointestinal tracts and in specific light organelles in deep-sea fish (30,47,48). P. phosphoreum is a bioluminescent bacterium (17, 46, 48) which can also be found in dim and dark versions; loss of bioluminescence among bioluminescent species is frequently observed (16,30,31,53). It is unknown if all nonbioluminescent P. phosphoreum strains have ever been able to produce light, although it has been shown that at least part of the essential lux genes is present in both the luminous and nonluminous strains (17). P. phosphoreum belongs to the Vibrionaceae, which harbor several bioluminescent species, including Vibrio fischeri and Vibrio harveyi. These two species regulate bioluminescence through a circuit popularly referred to as quorum sensing (22,50,54). In brief, quorum sensing involves the production and release of communication molecules, which accumulate in the surrounding environment and allow the bacteria to coregulate specific phenotypes. The communication molecules regulating bioluminescence in V. fischeri are N-acylated homoserine lactones (AHLs). Quorum sensing enables V. fischeri to up-regulate bioluminescence when situated in its symbiont Euprymna scolopes and abolish light production when in the free-living state in t...

N-acyl-homoserine lactone-mediated quorum-sensing in Azospirillum: an exception rather than a rule

“…Transposon mutagenesis was not attempted on strain B518 as it was found to be of no use in A. lipoferum strains, mainly due to the extremely low frequency of plasmid transfer (Bally & Givaudan, 1988;our unpublished results). Recently, unsuccessful attempts to clone quorum-sensing genes in Phosphobacterium phosphoreum were reported, although genetic techniques were implemented in this model (Flodgaard et al, 2005). Synthesis of several different AHLs by a single LuxI homologue has been reported previously.…”

Biofilms in the Spotlight: Detection, Quantification, and Removal Methods

“…Moreover, they found AHLs in different spoiled commercial fish products (for example, minced fish, fish fillets, and smoked salmon), indicating their potential role in quorum sensing systems. Another study by the same research group demonstrated that 2 different strains, Photobacterium phosphoreum and Aeromonas spp., which are involved in regulating chitinase activity and are responsible for crustacean degradation (Flodgaard et al., ), isolated from the spoilage microflora of cod fillets were able to produce AHLs. Regarding milk and dairy product spoilage, Ammor et al.…”

Phylogeny, genomics, and symbiosis ofPhotobacterium

“…The nonluminous Clade 1 species, P. iliopiscarium (Onarheim et al, 1994;Urakawa et al, 1999), was isolated from the intestines of several species of cold-water fish and has been recovered from spoiled packaged fish (e.g. Ast & Dunlap, 2005;Flodgaard et al, 2005). In many of these associations, such as commensal and saprophytic associations, Photobacterium species occur together in mixed assemblages with many other kinds of bacteria.…”