Detection and quantification of Vibrio fischeri autoinducer from symbiotic squid light organs

Abstract

Vibrio fischeri is the specific light organ symbiont of the sepiolid squid species Euprymna scolopes and Euprymna morsei. Both species of squid are luminescent by virtue of their bacterial symbionts, but the natural symbionts of E. scolopes do not produce visible luminescence in laboratory culture. The primary cause of this depressed luminescence by E. scolopes symbionts in culture was found to be the production of relatively low levels of V. fischeri autoinducer, a positive transcriptional coregulator of the lux regulon, identified as N-(3-oxohexanoyl) homoserine lactone. Concentrations of autoinducer activity produced by these symbionts in culture were quantified and found to be at least 10-fold lower than those produced by E. morsei isolates (which are visibly luminous outside the association) and perhaps 10,000-fold lower than those of the brightest V. fischeri strains. Despite the differences in their symbiont strains, the intact light organs of the two species of squid contained comparable amounts of extractable autoinducer activity (between 100 and 200 pg per adult animal). The chromatographic behavior of this autoinducer activity on reverse-phase high-performance liquid chromatography was consistent with its presumptive identification as V. fischeri autoinducer. Within the 5-l volume of the epithelial core of the light organ in which the symbiotic V. fischeri strains are housed, these amounts would result in an effective autoinducer concentration of at least 100 nM. Because these levels are over 40-fold higher than the concentration needed for the induction of luminescence of bacteria in culture, we conclude that the inherent degree of autoinducer production by strains of V. fischeri may not influence their effectiveness as light organ symbionts. Furthermore, this study provides the first direct evidence that the phenomenon of cell density-dependent autoinduction, discovered and described first for laboratory cultures of V. fischeri but believed to be a general phenomenon in many species of host-associated symbionts and pathogens, is in fact a consequence of bacterial colonizations of host tissue.

IL-8 Production in Human Lung Fibroblasts and Epithelial Cells Activated by the Pseudomonas Autoinducer N-3-Oxododecanoyl Homoserine Lactone Is Transcriptionally Regulated by NF-κB and Activator Protein-2

“…Because 3-O-C12-HSL freely diffuses and is actively pumped out of the bacteria, it would directly interact with epithelial cells (37). Previous data have shown that in the squid, where the symbiotic bacteria V. fisheri produces an autoinducer similar to P. aeruginosa (3-O-C6-HSL), this molecule was found not only in the area around the bacteria, but was detected also in the underlying epithelial cells (38). These observations support the hypothesis that 3-O-C12-HSL produced by P. aeruginosa interacts with the surrounding tissue.…”

“…Studies with V. fisheri have shown that the concentration of Vibrio autoinducer isolated from the light organs of squids was up to 200-fold higher than that produced by the bacteria in culture (38). There is also evidence that when Pseudomonas is grown in a biofilm the concentration of autoinducers produced is significantly higher than that of planktonic bacteria.…”

The Pseudomonas Autoinducer N-(3-Oxododecanoyl) Homoserine Lactone Induces Cyclooxygenase-2 and Prostaglandin E2 Production in Human Lung Fibroblasts: Implications for Inflammation

“…Because 3O-C 12 -HSL is both diffused and pumped out of P. aeruginosa, it directly interacts with surrounding eukaryotic cells (5). In studies examining the colonization of squid light organs with the bacteria Vibrio fischeri, which produces an AHL similar to 3O-C 12 -HSL, it was observed that the AHL not only was located around the bacteria but had penetrated into the epithelial layer of the light organ (37). We propose that 3O-C 12 -HSL produced by P. aeruginosa may have a similar interaction with the epithelium of the lung.…”

Quorum size of Pseudomonas syringae is small and dictated by water availability on the leaf surface

“…For example, because many as 10 8 cells of the bacterial symbiont Vibrio fisherii can be found within the light organs of an adult bobtail squid. This community accumulates 3OC6-HSL to concentrations exceeding 100 nm, Ͼ40 times the concentration needed to induce QS induction and thus bioluminescence in liquid culture (39). The squid light organ epithelial cells (35) and lung epithelial tissue (40) apparently do not provide a complete barrier to diffusion of 3OC6-HSL and yet signal may still accumulate in organs.…”