Abstract
BackgroundQuorum Sensing (QS) is a cell-to-cell communication system that bacteria utilize to adapt to the external environment by synthesizing and responding to signalling molecules called autoinducers. The psychrotrophic bacterium Aliivibrio wodanis 06/09/139, originally isolated from a winter ulcer of a reared Atlantic salmon, produces the autoinducer N-3-hydroxy-decanoyl-homoserine-lactone (3OHC10-HSL) and encodes the QS systems AinS/R and LuxS/PQ, and the master regulator LitR. However, the role of QS in this bacterium has not been investigated yet.ResultsIn the present work we show that 3OHC10-HSL production is cell density and temperature-dependent in A. wodanis 06/09/139 with the highest production occurring at a low temperature (6 °C). Gene inactivation demonstrates that AinS is responsible for 3OHC10-HSL production and positively regulated by LitR. Inactivation of ainS and litR further show that QS is involved in the regulation of growth, motility, hemolysis, protease activity and siderophore production. Of these QS regulated activities, only the protease activity was found to be independent of LitR. Lastly, supernatants harvested from the wild type and the ΔainS and ΔlitR mutants at high cell densities show that inactivation of QS leads to a decreased cytopathogenic effect (CPE) in a cell culture assay, and strongest attenuation of the CPE was observed with supernatants harvested from the ΔlitR mutant.ConclusionA. wodanis 06/09/139 use QS to regulate a number of activities that may prove important for host colonization or interactions. The temperature of 6 °C that is in the temperature range at which winter ulcer occurs, plays a role in AHL production and development of CPE on a Chinook Salmon Embryo (CHSE) cell line.
Highlights
Quorum sensing (QS) is a cell–cell communication mechanism regulated by secretion and accumulation of small diffusible signalling molecules called autoinducers (AI) in a cell density-dependent manner (Bassler, 1999)
Our analysis show that the Quorum Sensing (QS) system in A. wodanis regulates various phenotypic traits such as motility, growth, hemolysis, protease, siderophore production, as well as cytotoxicity in a cell line
Since ainS is the only acyl homoserine lactones (AHLs)-linked gene annotated in A. wodanis we find other explanations unlikely
Summary
Quorum sensing (QS) is a cell–cell communication mechanism regulated by secretion and accumulation of small diffusible signalling molecules called autoinducers (AI) in a cell density-dependent manner (Bassler, 1999). In Gram-negative bacteria, the most common signalling molecules used for intra-species communication are N-acyl homoserine lactones (AHLs) referred to as AI-1. At high cell density, the autoinducers bind to their cognate receptors leading to dephosphorylation of LuxO and litR expression. The psychrotrophic bacterium Aliivibrio wodanis 06/09/139, originally isolated from a winter ulcer of a reared Atlantic salmon, produces the autoinducer N-3-hydroxy-decanoyl-homoserine-lactone (3OHC10HSL) and encodes the QS systems AinS/R and LuxS/PQ, and the master regulator LitR. Inactivation of ainS and litR further show that QS is involved in the regulation of growth, motility, hemolysis, protease activity and siderophore production. The temperature of 6 ◦C that is in the temperature range at which winter ulcer occurs, plays a role in AHL production and development of CPE on a Chinook Salmon Embryo (CHSE) cell line
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