Lactococcus lactis uses MscL as its principal mechanosensitive channel
ABSTRACT The functions of the mechanosensitive channels from Lactococcus lactis were determined by biochemical, physiological, and electrophysiological methods. Patch-clamp studies showed that the genes yncB and mscL encode MscS and MscL-like channels, respectively, when expressed in Escherichia coli or if the gene products were purified and reconstituted in proteoliposomes. However, unless yncB was expressed in trans, wild type membranes of L. lactis displayed only MscL activity. Membranes prepared from an mscL disruption mutant did not show any mechanosensitive channel activity, irrespective of whether the cells had been grown on low or high osmolarity medium. In osmotic downshift assays, wild type cells survived and retained 20% of the glycine betaine internalized under external high salt conditions. On the other hand, the mscL disruption mutant retained 40% of internalized glycine betaine and was significantly compromised in its survival upon osmotic downshifts. The data strongly suggest that L. lactis uses MscL as the main mechanosensitive solute release system to protect the cells under conditions of osmotic downshift.
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ABSTRACT: Temperate bacteriophages are a contributor of the genetic diversity in the lactic acid bacterium Oenococcus oeni. We used a classification scheme for oenococcal prophages based on integrase gene polymorphism, to analyze a collection of Oenococcus strains mostly isolated in the area of Bordeaux, which represented the major lineages identified through MLST schemes in the species. Genome sequences of oenococcal prophages were clustered into four integrase groups (A to D) which were related to the chromosomal integration site. The prevalence of each group was determined and we could show that members of the intB- and intC-prophage groups were rare in our panel of strains. Our study focused on the so far uncharacterized members of the intD-group. Various intD viruses could be easily isolated from wine samples, while intD lysogens could be induced to produce phages active against two permissive O. oeni isolates. These data support the role of this prophage group in the biology of O. oeni. Global alignment of three relevant intD-prophages revealed significant conservation and highlighted a number of unique ORFs that may contribute to phage and lysogen fitness.International journal of food microbiology 07/2013; 166(2):331-340. DOI:10.1016/j.ijfoodmicro.2013.06.032 · 3.16 Impact Factor
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ABSTRACT: To obtain a gene construct for making single substitutions per channel and to determine the quaternary structure of the mechanosensitive channel MscL from Escherichia coli, covalent oligomers (monomer to hexamer) were engineered by gene fusion; up to six copies of the mscL gene were fused in tandem. All the multimeric tandem constructs yielded functional channels with wild-type conductance and dwell times. Importantly, only the covalent pentamer opened at the same relative pressure (compared to the pressure required to open MscS) as the wild-type MscL channel. The in vivo data strongly suggest that pentameric MscL represents the functional state of the channel.Protein Science 01/2006; 14(12):2947-54. DOI:10.1110/ps.051679005 · 2.86 Impact Factor