Presence of acyl-homoserine lactones in 57 members of the Vibrionaceae family.

AIMS: The aim of this study was to use a sensitive method to screen and quantify 57 Vibrionaceae strains for the production of acyl-homoserine lactones (AHLs) and map the resulting AHL profiles onto a host phylogeny. METHODS AND RESULTS: We used a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) protocol to measure AHLs in spent media after bacterial growth. First, the presence/absence of AHLs (qualitative analysis) was measured to choose internal standard for subsequent quantitative AHL measurements. We screened 57 strains from three genera (Aliivibrio, Photobacterium and Vibrio) of the same family (i.e. Vibrionaceae). Our results show that about half of the isolates produced multiple AHLs, typically at 25-5000 nmol l(-1) . CONCLUSIONS: This work shows that production of AHL quorum sensing signals is found widespread among Vibrionaceae bacteria and that closely related strains typically produce similar AHL profiles. SIGNIFICANCE AND IMPACT OF THE STUDY: The AHL detection protocol presented in this study can be applied to a broad range of bacterial samples and may contribute to a wider mapping of AHL production in bacteria, for example, in clinically relevant strains.

Supercooled liquid-like solvent in trypsin crystals: implications for crystal annealing and temperature-controlled X-ray radiation damage studies.

The study of temperature-dependent physical changes in flash-cooled macromolecular crystals is pertinent to cryocrystallography and related issues such as crystal annealing, X-ray radiation damage and kinetic crystallography. In this context, the unit-cell volume of flash-cooled trigonal and orthorhombic trypsin crystals has been monitored upon warming from 100 to 200 K and subsequent re-cooling to 100 K. Crystals of both forms were obtained under the same crystallization conditions, yet they differ in solvent content and channel size. An abrupt non-reversible unit-cell volume decrease is observed at 185 K in orthorhombic and at 195 K in trigonal crystals as the temperature is increased; this result is consistent with ultra-viscous solvent leaving the crystals. Concomitant appearance of ice rings in the diffraction patterns suggests that the transported solvent forms crystalline ice. These results demonstrate that solvent in flash-cooled protein crystals is liquid-like near its crystallization temperature, as has been proposed, yet controversially discussed, for the case of pure water. The use of mineral oil prevents the unit-cell volume decrease in trigonal but not in orthorhombic crystals. The observation of liquid-like solvent has implications in the development of annealing protocols and points a way to the rational design of temperature-controlled crystallographic studies that aim either at studying specific radiation damage or at trapping enzymatic intermediate states.