A probable aculeacin A acylase from the Ralstonia solanacearum GMI1000 is N-acyl-homoserine lactone acylase with quorum-quenching activity

<p>Abstract</p> <p>Background</p> <p>The infection and virulence functions of diverse plant and animal pathogens that possess quorum sensing systems are regulated by <it>N</it>-acylhomoserine lactones (AHLs) acting as signal molecules. AHL-acylase is a quorum quenching enzyme and degrades AHLs by removing the fatty acid side chain from the homoserine lactone ring of AHLs. This blocks AHL accumulation and pathogenic phenotypes in quorum sensing bacteria.</p> <p>Results</p> <p>An <it>aac </it>gene of undemonstrated function from <it>Ralstonia solanacearum </it>GMI1000 was cloned, expressed in <it>Escherichia coli</it>; it inactivated four AHLs that were tested. The sequence of the 795 amino acid polypeptide was considerably similar to the AHL-acylase from <it>Ralstonia </it>sp. XJ12B with 83% identity match and shared 39% identity with an aculeacin A acylase precursor from the gram-positive actinomycete <it>Actinoplanes utahensis</it>. Aculeacin A is a neutral lipopeptide antibiotic and an antifungal drug. An electrospray ionisation mass spectrometry (ESI-MS) analysis verified that Aac hydrolysed the amide bond of AHL, releasing homoserine lactone and the corresponding fatty acids. However, ESI-MS analysis demonstrated that the Aac could not catalyze the hydrolysis of the palmitoyl moiety of the aculeacin A. Moreover, the results of MIC test of aculeacin A suggest that Aac could not deacylate aculeacin A. The specificity of Aac for AHLs showed a greater preference for long acyl chains than for short acyl chains. Heterologous expression of the <it>aac </it>gene in <it>Chromobacterium violaceum </it>CV026 effectively inhibited violacein and chitinase activity, both of which were regulated by the quorum-sensing mechanism. These results indicated that Aac could control AHL-dependent pathogenicity.</p> <p>Conclusion</p> <p>This is the first study to find an AHL-acylase in a phytopathogen. Our data provide direct evidence that the functioning of the <it>aac </it>gene (NP520668) of <it>R. solanacearum </it>GMI1000 is via AHL-acylase and not via aculeacin A acylase. Since Aac is a therapeutic potential quorum-quenching agent, its further biotechnological applications in agriculture, clinical and bio-industrial fields should be evaluated in the near future.</p

Clinical efficacy for ptosis patients with severe undercorrection after frontal muscle flap suspension surgery

AIM: To observe the treatment for ptosis patients with severe undercorrection after frontal muscle flap suspension surgery.METHODS: Totally 46 patients(67 eyes)were randomly divided into 2 groups: 23 cases(33 eyes)in Group A were given conjoint fascial sheath(CFS)suspension surgery; 23 cases(34 eyes)in Group B Whitnall ligament suspension. Postoperative follow-up was 6mo. Corrected rate, recurrence rate and postoperative adverse reactions were compared and analyzed. RESULTS:The corrected rates of the two groups were both satisfied without significant difference between the two groups(P>0.05). the Whitnall ligament suspension surgery had less recurrence than CFS suspension surgery, but the difference was not statistically significant(P>0.05). The rate of hypophasis after CFS suspension surgery was significantly less than that after Whitnall ligament suspension(PCONCLUSION: The two operations both have satisfied corrected rate and low recurrence rate, the Whitnall ligament suspension surgery is less damaging and more easy to operate, while CFS suspension surgery is repeatable and less rate of hypophasis

Bis[3-(meth­oxy­carbon­yl)anilinium] hexa­chloridostannate(IV)

In the title compound, (NH3C6H4CO2CH3)2[SnCl6], the anions are situated on inversion centers so the asymmetric unit contains one cation and one half-anion. In the crystal, inter­molecular N—H⋯Cl and N—H⋯O hydrogen bonds link the cations and anions into layers parallel to the ac plane. The crystal packing exhibits voids of 37 Å3