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Impact of osmotic stress on protein diffusion in L actococcus lactis
Author(s) -
Mika Jacek T.,
Schavemaker Paul E.,
Krasnikov Victor,
Poolman Bert
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12800
Subject(s) - osmotic shock , biology , osmotic concentration , lactococcus lactis , population , diffusion , osmotic pressure , biophysics , biochemistry , bacteria , lactic acid , genetics , thermodynamics , gene , demography , physics , sociology
Summary We measured translational diffusion of proteins in the cytoplasm and plasma membrane of the G ram‐positive bacterium L actococcus lactis and probed the effect of osmotic upshift. For cells in standard growth medium the diffusion coefficients for cytosolic proteins (27 and 582 kDa) and 12‐transmembrane helix membrane proteins are similar to those in E scherichia coli . The translational diffusion of GFP in L . lactis drops by two orders of magnitude when the medium osmolality is increased by ∼ 1.9 O sm, and the decrease in mobility is partly reversed in the presence of osmoprotectants. We find a large spread in diffusion coefficients over the full population of cells but a smaller spread if only sister cells are compared. While in general the diffusion coefficients we measure under normal osmotic conditions in L . lactis are similar to those reported in E . coli , the decrease in translational diffusion upon osmotic challenge in L . lactis is smaller than in E . coli . An even more striking difference is that in L . lactis the GFP diffusion coefficient drops much more rapidly with volume than in E . coli . We discuss these findings in the light of differences in turgor, cell volume, crowding and cytoplasmic structure of G ram‐positive and G ram‐negative bacteria.