D E P A R T M E N T O F F O O D S C I E N C E

1. Growth Conditions Influence Initial Adhesion and Cell Surface Characteristics of Listeria monocytogenes D E P A R T M E N T O F F O O D S C I E N C E F A C U L T Y O F L I F E S C I E N C E S U N I V E R S I T Y O F C O P E N H A G E N Anne Skovager*, Marianne H. Larsen**, Nils Arneborg* and Hanne Ingmer** * Department of Food Science, Food Microbiology, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg C, Denmark ** Department of Veterinary Disease Biology, Section for Microbiology, Faculty of Life sciences, University of Copenhagen, Stigbøjlen 4, 1870 Frederiksberg C, Denmark • Introduction • In the present work, it is hypothesized • that changes in nutrient composition • influence on the initial adhesion of • Listeria monocytogenes. The cell • characteristics may change as a • consequence of different nutrients • present. • Aim • The aim is to examine if different • nutrients (carbohydrates and amino • acids) alter the initial adhesion of L. monocytogenes to fine polished • stainless steel, and if so to determine • altered surface characteristics. • Conclusion • It can be concluded that specific • growth conditions (nutrients) have a • significant influence on the initial adhesion rate (IAR) of L. mono- • cytogenes on fine polished stainless steel and on the cell surface protein composition. • Methods • Strain/ growth condition • Listeria monocytogenes EGD/pNF8 • TSB + additional nutrients (22 h at 37°C) • Flow perfusion experiments • Fluorescence microscopy and a flow • perfusion system (shear stress: 0.10 Pa) was used for determination of IAR under liquid flow (cells/cm2*min) (Fig.2). • Results and Discussion • Different nutrients had an influence on IAR • (Fig.1A). • 2.5 g/L mannose and 2.5 g/L glucose • +100 mM L-leucine resulted in the lowest and highest IAR, respectively (P<0.05). • No correlation was found between cell size, • hydrophobicity, electron donating and accepting properties and IAR. • The different growth conditions resulted in • altered fatty acid composition, however it could not be correlated to IAR. • Expression of cell surface proteins was • dependent on the growth media composition, notably in the presence of 2.5 g/L mannose; 2.5 g/L glucose; and 2.5 g/L glucose + 100 mM L-leucine (Fig. 1B). • Proteins with altered expression will be • identified in the future. • Examine effect of: • Nutrients: • Glucose, mannose, fructose, • L-leucine, L-isoleucine, L-valine • On: • Initial adhesion under liquid flow • to stainless steel • Hydrophobicity and electron • accepting/donating properties (Microbial Adhesion To Solvents) • Cell size • Fatty acid composition • (GLC – of whole cells) • Cell surface proteins • (SDS-PAGE) A B Cells/cm2 ▲●♦ Figure 2. Experimental setup: The flow chambers are glued on fine polished stainless steel and placed under a fluorescence microscope, connected with a digital camera. The flow chamber is via tubes connected to two pumps. Between the inlet of the perfusion chamber and the inlet pump aflow equalizing system is installed. Time (min) Digitalcamera Figure 1. A) Initial adhesion of L. monocytogenes cells, grown with different nutrients (cells/cm2 vs. time). B) SDS-PAGE protein gel of cell surface proteins (3 growth conditions). Fluorescencemicroscope Pumps Sponsor: The Danish Research Council for Technology and Production Sciences; Contact:Anne Skovager, annesj@life.ku.dk Cellsuspension Flowequalizingsystem Waste Flowperfusionchamber