Glycine betaine improves Listeria monocytogenes tolerance to desiccation on parsley leaves independent of the osmolyte transporters BetL, Gbu and OpuC.
OBJECTIVE
To investigate the effect of glycine betaine (GB) on the survival of Listeria monocytogenes on leaf surfaces under low relative humidity (RH).


RESULTS
The addition of GB (> or = 25 mmol l(-1)) improved the survival of L. monocytogenes under low RH on parsley leaves, thus suggesting that GB can improve the tolerance of L. monocytogenes to desiccation. Ten times less GB was needed to improve L. monocytogenes survival under low RH on nonbiological surfaces compared with parsley leaves, suggesting that, on the leaf surface, L. monocytogenes may have to compete for the available GB with autochthonous bacteria and/or the plant itself. Wild type and mutants carrying deletions in the three GB uptake systems, BetL, Gbu and OpuC, behaved similarly with and without added GB on parsley leaves (P > 0.05). In addition, preaccumulation of GB, triggered by osmotic stress prior to inoculation, failed to improve survival under low RH compared with osmotic stress without GB accumulation.


CONCLUSIONS
Exogenous GB had a protective effect on L. monocytogenes cells from desiccation during survival on parsley leaves. This effect was independent of intracellular GB accumulation by the known uptake systems.


CONCLUSIONS
Presence of GB could improve the survival of L. monocytogenes to desiccation on leaf surfaces and nonbiological surfaces.
Dreux
N
N
INRA, UMR 408, Sécurité et Qualité des Produits d'Origine Végétale, Avignon, F-84914, France, Univ Avignon, Avignon, F-84029, France. ndreux@avignon.inra.fr
Albagnac
C
C
Sleator
R D
RD
Hill
C
C
Carlin
F
F
Morris
C E
CE
Nguyen-the
C
C
D001431:Bacteriological Techniques; D001622:Betaine / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport; D001693:Biological Transport, Active; D015169:Colony Count, Microbial; D003470:Culture Media; D003890:Desiccation; D005516:Food Microbiology; D008089:Listeria monocytogenes / Q000187:drug effects / Q000502:physiology*; D008088:Listeriosis / Q000635:transmission; D026901:Membrane Transport Proteins / Q000378:metabolism*; D050296:Microbial Viability; D009997:Osmotic Pressure; D028528:Petroselinum / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D014774:Virulence
D003470:Culture Media; D026901:Membrane Transport Proteins; D001622:Betaine