scophthalmi since they are so closely related. In V. scophthalmi, these two quorum-sensing systems may play a role in the colonization and establishment of this bacterium in the fish intestine, since it is a normal inhabitant of the turbot intestine [1]. In fact most vibrio species form biofilms on different structures, which is believed to be beneficial for the populations against different environmental stresses [19]. Work is currently being done to test these hypotheses. Staurosporine datasheet A difference in the expression of membrane proteins, which may relate to differences

in biofilm formation, was assessed by mass spectroscopy. In the case of the luxS mutant the intensity of m/z 4277 was significantly lower than m/z 4622 and m/z 4622 was significantly higher than m/z 5180, while in the wild type strain these ratios were reversed (p<0.01) (Figure 3). Similar results were obtained for the luxR mutant, suggesting that the expression of these proteins were affected by these mutations. Figure 3 Differential expression of membrane proteins in the (a) V. scophthalmi A102 luxS and (b) luxR mutants with respect to the (c) wild type strain analyzed

by mass spectrometry. The ratios of the major proteins with m/z 4277, 4622, 5180 are shown in the inset. Standard deviation of three independent measurements in brackets. Extracellular find more protease activity was not detected in either the wild-type strain or any of the luxR and/or luxS mutants as determined by a qualitative milk plate assay as well as a quantitative detection method

using azocasein. On the other hand, siderophore production, which has been shown to be regulated by quorum-sensing in other this website vibrios was evaluated using the siderophore CAS assay. In addition, the ability to grow in iron depleted medium (EDDA assay) was assessed. A minor positive signal indicating the presence of siderophore activity was detected in all the mutants and wild type strains with the same intensity. However, neither the wild-type strain nor the mutants grew in the EDDA-supplemented medium suggesting that this species is not able to grow in iron-depleted medium, at least under the conditions used in the assay. Extracellular proteases and siderophores are often produced by pathogenic vibrios [20–22], although some vibrios that are not pathogenic have been shown to produce siderophores Mirabegron in an iron-limited host environment, such as V. fischeri[23]. The Vibrio harveyi-like LuxR family of regulators is a diverse family with different associated functions depending on the Vibrio species. For example, in V. harveyi, luxR is expressed at high cell densities and regulates different functions including siderophores, colony morphology, activates bioluminescence, activates metalloprotease production, represses the type III secretion system [21, 24, 25]. Apart from this diversity, all the V. harveyi-like quorum-sensing systems converge to a phosphorelay circuit that regulates the expression of luxR.