In Helicobacter pylori auto-inducer-2, but not LuxS/MccAB catalysed reverse transsulphuration, regulates motility through modulation of flagellar gene transcription.

BACKGROUND: LuxS may function as a metabolic enzyme or as the synthase of a quorum sensing signalling molecule, auto-inducer-2 (AI-2); hence, the mechanism underlying phenotypic changes upon luxS inactivation is not always clear. In Helicobacter pylori, we have recently shown that, rather than functioning in recycling methionine as in most bacteria, LuxS (along with newly-characterised MccA and MccB), synthesises cysteine via reverse transsulphuration. In this study, we investigated whether and how LuxS controls motility of H. pylori, specifically if it has its effects via luxS-required cysteine metabolism or via AI-2 synthesis only. RESULTS: We report that disruption of luxS renders H. pylori non-motile in soft agar and by microscopy, whereas disruption of mccAHp or mccBHp (other genes in the cysteine provision pathway) does not, implying that the lost phenotype is not due to disrupted cysteine provision. The motility defect of the DeltaluxSHp mutant was complemented genetically by luxSHp and also by addition of in vitro synthesised AI-2 or 4, 5-dihydroxy-2, 3-pentanedione (DPD, the precursor of AI-2). In contrast, exogenously added cysteine could not restore motility to the DeltaluxSHp mutant, confirming that AI-2 synthesis, but not the metabolic effect of LuxS was important. Microscopy showed reduced number and length of flagella in the DeltaluxSHp mutant. Immunoblotting identified decreased levels of FlaA and FlgE but not FlaB in the DeltaluxSHp mutant, and RT-PCR showed that the expression of flaA, flgE, motA, motB, flhA and fliI but not flaB was reduced. Addition of DPD but not cysteine to the DeltaluxSHp mutant restored flagellar gene transcription, and the number and length of flagella. CONCLUSIONS: Our data show that as well as being a metabolic enzyme, H. pylori LuxS has an alternative role in regulation of motility by modulating flagellar transcripts and flagellar biosynthesis through production of the signalling molecule AI-2

An Industrial Approach to High Gradient Magnetic Fishing in the Food Industry

High-gradient magnetic filtration bases on the separation of target media by synthetic particles with magnetic core and an adsorbent immobilized on the surface. The process was used in a pilot line at liter-scale for the separation of a protein Bowman-Birk protease Inhibitor (BBI) out of an industrial coproduct stream in the soy industry. The target protein has potential applications as pharmaceutical or food additive. The starting medium is challenging as the product cost is low, its concentration is low and its purity needs to be high. The main method tested was magnetically enhanced centrifugation in a batch-wise mode with anion exchange ligands. The separation of the target protein at large scale was successful and economical. The efficiency was low due to the low ligand selectivity and the batch-wise processing. For commercialization, high ligand selectivity and continuous processing would make this new magnetic separation process very attractive. An economic study was performed to determine the influence of different parameters on prices. Competing technologies were evaluated. A risk analysis of nanoparticles used in the pilot line was performed