|
|
|
|
|
|
Quorum Quenching: Enzymatic Disruption of N-Acylhomoserine Lactone-Mediated Bacterial Communication in Burkholderia thailandensis. Ricky L. Ulrich, 2004.Many species of gram-negative bacteria communicate by synthesizing, secreting, and responding to N-acylhomoserine lactones (AHLs), a mechanism termed quorum sensing . Several investigations have characterized numerous AHL-degrading enzymes (AiiA lactonases) encoded by environmental isolates of Bacillus spp . The Burkholderia thailandensis quorum system is comprised of at least three AHL synthases (AHSs) and five transcriptional regulators belonging to the LuxIR class of proteins . Expression of the Bacillus anthracis (Ames strain) AiiA lactonase in B . thailandensis completely abolished the accumulation of N-decanoylhomoserine lactone (C10-HSL) and N-octanoylhomoserine lactone (C8-HSL), reduced N-hexanoylhomoserine lactone (C6-HSL) levels, altered both swarming and twitching motility, caused a significant increase in generation time, and affected carbon metabolism . In contrast, heterologous expression of the Bacillus cereus strain A24 AiiA lactonase in B . thailandensis reduced the concentrations of C6-HSL, C8-HSL, and C10-HSL to nondetectable levels; altered both swarming and twitching motility; and caused fluctuations in carbon utilization . Individual disruption of the B . thailandensis AHSs, specifically disruption of the btaI1 and btaI3 genes, which encode the proteins that direct the synthesis of C8-HSL and C6-HSL, respectively, caused the hyper-beta-hemolysis of sheep erythrocytes on blood agar plates . In contrast, AHL cleavage in B . thailandensis by the Bacillus AiiA lactonases failed to enhance beta-hemolytic activity . The results of this study demonstrate that heterologous expression of Bacillus sp . AiiA lactonases in B . thailandensis reduced AHL accumulation, affected both swarming and twitching motility, increased generation time, altered substrate utilization, and prevented the beta-hemolysis of sheep erythrocytes . Subcellular Localization of a Small Sporulation Protein in Bacillus subtilis. Christiaan van Ooij, 2003.SpoVM is an unusually small (26-residue-long) protein that is produced in the mother cell chamber of the sporangium during the process of sporulation in Bacillus subtilis . We investigated the subcellular localization of SpoVM, which is believed to be an amphipathic  -helix, by using a fusion of the sporulation protein to the green fluorescence protein (GFP) . We found that SpoVM-GFP is recruited to the polar septum shortly after the sporangium undergoes asymmetric division and that the fusion protein localizes to the mother cell membrane that surrounds the forespore during the subsequent process of engulfment . We identified a patch of three residues near the N terminus of the proposed
-helix that is needed both for proper subcellular localization and for SpoVM function . We also identified a patch of residues on the opposite face of the helix and residues near both ends of the protein that are needed for SpoVM function but not for subcellular localization . Subcellular localization of SpoVM-GFP was found to require an unknown gene(s) under the control of the mother cell transcription factor
 E . We propose that the N-terminal patch binds to an unknown anchoring protein that is produced under the control of
E and that other residues important in SpoVM function to recruit an unknown sporulation protein(s) to the mother cell membrane that surrounds the forespore . Our results provide evidence that SpoVM function depends on proper subcellular localization .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
