Intracellular Ca(2+) mobilization and kinase activity during acylated homoserine lactone-dependent quorum sensing in Serratia liquefaciens.
Quorum sensing in Gram-negative bacteria involves acylated homoserine lactones (AHLs) and a transcription factor, activated by the AHLs. In this study, a possible involvement of intracellular Ca(2+) as second messenger and/or protein kinase activity during signal transduction is analyzed. When N-hexanoyl-l-homoserine lactone was added to a suspension of Fura-2-loaded Serratia liquefaciens, there was a decline in [Ca(2+)](i), measured as a decrease in the Fura-2 fluorescence ratio. As controls, the addition of the signal molecule N-3-oxohexanoyl-l-homoserine lactone, which is not produced by S. liquefaciens, did not induce changes in [Ca(2+)](i). Using a protein kinase activity assay on AHL-stimulated cells, an increase in kinase activity after N-butanoyl-l-homoserine lactone stimulation of S. liquefaciens cells was detected, whereas the kinase activity induced by N-3-oxohexanoyl-l-homoserine lactone was not statistically significant. The conclusion from this study is that changes in [Ca(2+)](i) are involved in quorum sensing signal transduction in the Gram-negative bacteria S. liquefaciens. We also conclude that kinase activity is induced in S. liquefaciens upon AHL stimulation. We suggest that the transient intracellular [Ca(2+)] changes and kinase activity, activated by the AHL signal, are critical for the quorum-sensing signal transduction.
Werthén
M
M
Department of Cell and Molecular Biology/Microbiology, Göteborg University, Göteborg SE-405 30, Sweden. maria.werthen@gmm.gu.se
Lundgren
T
T
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000502:physiology*; D012097:Repressor Proteins / Q000502:physiology; D012705:Serratia / Q000502:physiology*; D015398:Signal Transduction; D015534:Trans-Activators / Q000502:physiology
D012097:Repressor Proteins; D015534:Trans-Activators; C064778:LuxR autoinducer binding proteins; C088386:homoserine lactone; D011494:Protein Kinases; D015107:4-Butyrolactone; D002118:Calcium