001. Claire Passarelli, Tarik Meziane, Najet Thiney, Dominique Boeuf, Bruno Jesus, Mickael Ruivo, Christian Jeanthon, Cédric Hubas. UMR BOREA 7208 CNRS/MNHN/UPMC/IRD, Muséum National d'Histoire Naturelle, Bâtiment des Arthropodes, CP53, 61 rue Buffon, 75231 Paris Cedex 5, France. Seasonal variations of the composition of microbial biofilms in sandy tidal flats: Focus of fatty acids, pigments and exopolymers. Estuarine, Coastal and Shelf Science, 153, 2015, Page: 29 – 37.

     Biofilms, or microbial mats, are common associations of microorganisms in tidal flats; they generally consist of a large diversity of organisms embedded in a matrix of Extracellular Polymeric Substances (EPS). These molecules are mainly composed of carbohydrates and proteins, but their detailed monomer compositions and seasonal variations are currently unknown. Yet this composition determines the numerous roles of biofilms in these systems. This study investigated the changes in composition of carbohydrates in intertidal microbial mats over a year to decipher seasonal variations in biofilms and in varying hydrodynamic conditions. This work also aimed to assess how these compositions are related to microbial assemblages. In this context, natural biofilms whose development was influenced or not by artificial structures mimicking polychaete tubes were sampled monthly for over a year in intertidal flats of the Chausey archipelago. Biofilms were compared through the analysis of their fatty acid and pigment contents, and the monosaccharide composition of their EPS carbohydrates. Carbohydrates from both colloidal and bound EPS contained mainly glucose and, to a lower extent, galactose and mannose but they showed significant differences in their detailed monosaccharide compositions. These two fractions displayed different seasonal evolution, even if glucose accumulated in both fractions in summer; bound EPS only were affected by artificial biogenic structures. Sediment composition in fatty acids and pigments showed that microbial communities were dominated by diatoms and heterotrophic bacteria. Their relative proportions, as well as those of other groups like cryptophytes, changed between times and treatments. The changes in EPS composition were not fully explained by modifications of microbial assemblages but also depended on the processes taking place in sediments and on environmental conditions. These variations of EPS compositions are likely to alter different ecosystem processes such as biostabilisation or pollutants trapping.

Keywords: biofilms; biogenic structures; EPS; monosaccharide composition; fatty acids; pigments.

002. Huhu Wang, Xinxiao Zhang, Qiuqin Zhang, Keping Ye, Xinglian Xu, Guanghong Zhou.Key Laboratory of Meat Processing and Quality Control, Ministry of Education, College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, PR China.Comparison of microbial transfer rates from Salmonella spp. biofilm growth on stainless steel to selected processed and raw meat. Food Control, 50, 2015, Page: 574 – 580.

      Salmonella biofilm cells can serve as a serious source of cross-contamination, both in the home and at food production sites. The objectives of this study were to determine the transfer rates (RTs) of Salmonella biofilm cells and to model the transfer process of biofilm cells from stainless steel surfaces to raw meat. The results showed that the RTs were significantly influenced by the types of meat products, with bacon and emulsified sausage showing higher RTs and roast pork showing lower RTs. Higher RTs of biofilm grown in a meat-based medium, Meat Thawing-Loss Broth (MTLB), were observed as compared to that in a standard growth medium (TSB). The logistic, exponential and multi-roots models could be used to satisfactorily describe the transfer of biofilm cells as demonstrated by use of MSE, F-test and R2. There was no difference in attachment strength (reflected by the coefficients of transfer models) of biofilm grown in TSB or MTLB, as shown by the coefficients of r, D and B in three models. Compared with the exponential and the multi-roots models, the logistic model was able to more accurately fit the whole transfer process of biofilm cells. Our findings highlight the occurrence of cross-contamination with biofilm cells, and the models may provide useful tools in quantitative microbiological risk assessment of meat products.

Keywords: Salmonella; Biofilm; Transfer; Meat; Models