The findings

that the maximum production of BDSF occurred ahead from the other two signals suggest that these precursors are produced differentially during bacterial growth. The notion is agreeable with the observations that the medium composition affected the ratio of the 3 DSF-family signals (Fig. 6). The previous work on Xcc revealed that the unsaturated double bond at the α,β position of DSF is important for it signalling activity and the saturated derivative is about 20,000 times less active than DSF [5]. BDSF is structurally different from DSF in the methyl substitution KU55933 concentration at the C-11 position (Fig. 2C). Similarly, DSF and BDSF had comparable effects on EPS production and on extracellular xylanase activity in Xoo, but CDSF was less active than its two analogues (Fig. 3). Presumably, the extra double bond at the C5-C6 of CDSF may affect its configuration, which hinders its accessibility to across the outer membrane or interaction with the sensor kinase. Consistent with this notion, farnesoic acid (3,7,11-trimethyl-2,6,10-dodecatrienoate), which contains two more double bonds in addition to the α,β double bond, shows a lower biological activity than DSF in Xcc [5].

Taken together, check details our results suggest that the DSF signalling mechanisms, especially at the level of the signal production autoregulation, are likely highly conserved in Xcc and Xoo. Conclusions Xoo strain KACC10331 produces multiple DSF-family

signals, including DSF, BDSF and CDSF, when grown in rich media. Xoo uses a similar mechanism as previously described in Xcc to autoregulate the biosynthesis of the DSF-family signals. All the three DSF-family molecules are Calpain active signals in induction of the virulence factor production in Xoo although the efficiency may vary. The amount and ratio of the DSF-family signals produced by Xoo are influenced by culture medium composition. Methods Bacterial selleck products strains and growth conditions Xoo wild type strain KACC10331 and the derivates were described previously [25]. Xoo strains were routinely grown at 30°C in YEB medium with 10 μg/ml cephalexin unless otherwise stated, which comprises 5 g/L yeast extract, 10 g/L tryptone, 5 g/L sodium chloride, 5 g/L sucrose, 0.5 g/L MgSO4. The NYG medium comprises 5 g/L peptone, 3 g/L yeast extract and 20 g/L glycerol. PSA medium contains 10 g/L peptone, 10 g/L sucrose, and 1.0 g/L Na-glutamate. The composition of XOLN medium: K2HPO4 0.7 g/L, KH2PO4 0.2 g/L, (NH4)2SO4 1 g/L, MgCl2 0.1 g/L, FeSO4 0.01 g/L, MnCl2 0.001 g/L, 0.0625% tryptone, 0.0625% yeast extract, sucrose 2 g/L [30]. All tryptone, peptone and yeast extract were from Becton, Dickinson and Company (USA). Bioassay and quantification analysis of DSF-like signals DSF bioassay and quantification was performed as described previously [5].