FERMENTED BEVERAGE
A. Yépez1, M. Juárez del Valle2, P. Elizaquível1, J.G. Le Blanc2, G. Vignolo2, P.S. Cocconcelli3, R. Aznar1
1Microbiología y Ecología, Universitat de València, Burjassot-Valencia, Spain 2Tecnología y Desarrollo, Centro de Referencia para Lactobacilos (CERELA),
San Miguel de Tucumán, Argentina
3Istituto di Microbiologia-Centro Ricerche Biotecnologiche,
Universitá Cattolica del Sacro Cuore, Piacenza-Cremona, Italy Background
Many lactic acid bacteria strains show extraordinary metabolic abilities, which are interesting for their application in functional food development such as group B vitamin overproduction. In this context, the determination of quality and food safety related traits i.e. antibiotic resistance are required.
Objectives
In this study, 29 Lactobacillus plantarum strains isolated from chicha, a traditional maize-based fermented Andean beverage, were previously selected by their ability to produce folic acid. Thus, we focused on evaluating additional activities relevant to functional food industry and to food safety and quality.
Methods
Lactobacillus plantarum strains were screened for riboflavin production (by reverse phase HPLC with fluorescence detector) and for the presence of riboflavin production related genes (ribA, ribB, ribC, ribG and ribH), antibacterial activity (Gaudana et al. 2010. Brit J Nutr. 103: 1620–1628) and antifungal activity (Magnusson et al. 2003. FEMS Microbiol Lett. 219:129-135). Regarding food safety, antibiotics resistance was tested as recommended by EFSA (2012) for Lb. plantarum.
Conclusions
Most strains strongly inhibited the growth of Listeria innocua CECT 910T, Escherichia
coli CECT 5947, Salmonella enterica CECT 4138 and showed antifungal activity against Aspergillus oryzae CECT 2094. Some of them, inhibited Aspergillus niger CECT 2807, as well. Among them, four strains exhibited traits of interest for the functional food industry. They produced 400ng/ml riboflavin, determined by HPLC, and showed the amplification products corresponding to genes in the riboflavin synthetic pathway. All of these were sensitive to the antibiotics tested and were able to inhibit the growth of relevant food pathogens and spoiler fungi.
FEMS-1244
Molecular principles of biofilm formation and dispersion
Regulation of functional interferences between Escherichia coli type 1 fimbriae and Ag43 phase-variable adhesins
J.M. Ghigo1
1Department of Microbiology, Institut Pasteur, Paris, France
Bacteria use a large number of adhesins involved in bacteria/surfaces and
bacteria/bacteria interactions to colonize their environments. In Escherichia coli, there are two essential and prototypic adhesins: the chaperone-usher type 1 fimbriae, involved in mannose-dependent interactions to host cells, and the auto-transporter adhesin Ag43, mediating bacterial auto-aggregation. These two adhesins are regulated by two distinct phase variation mechanisms: a promoter recombination inversion for type 1 fimbriae and an epigenetic mechanism involving the Dam methylase and the oxidative stress regulator OxyR for the auto-transporter adhesin Ag43. Since expression of long type 1 fimbriae physically interferes with short Ag43 adhesins, the functions of these two adhesins are antagonistic, which raises the question of how E. coli coordinates their expression. I will describe previously
unsuspected regulatory connection between phase variation mechanisms and stress responses and discuss how it contributes to coordinate the expression and exposition of E. coli surface adhesins and bacterial colonization capacity.
FEMS-2380
Molecular principles of biofilm formation and dispersion Molecular basis of dispersion and signal transduction K. Sauer1
1Biological Scinces, Binghamton University, Binghamton, USA
The process of biofilm dispersion represents an important phenotypic switch that allows cells residing within a biofilm to respond to changing conditions outside and within biofilm structures and to evade environmental stresses. Dispersion occurs in response to a wide array of signals, with dispersion-inducing conditions ranging from environmental cues to self-synthesized signaling molecules. Previous findings indicate biofilm dispersion by Pseudomonas aeruginosa to occur in response to various cues, to require BdlA and phosphodiesterases (PDEs, for instance DipA and RbdA), and to coincide with increased PDE activity and a reduction of c-di-GMP levels. However, little is known about dispersion cue sensing, the signaling events translating these cues into the modulation c-di-GMP levels, and the subsequent signaling cascade to enable dispersion resulting in the phenotypic switch. The presentation will focus on recent findings indicating how dispersion cue perception is translated across cellular compartments into the modulation of the intracellular c-di- GMP pool, the molecular events associated with signal transduction, and subsequent events associated with the induction of dispersion.
FEMS-2675
Molecular principles of biofilm formation and dispersion ADHESIN PROTEINS IN BACILLUS CEREUS BIOFILMS. J. Caro-Astorga1, A. Perez-García1, A. de Vicente1, D. Romero1
1Microbiologia, Facultad de Ciencias., Málaga, Spain
Background
The human pathogen Bacillus cereus is responsible for many recurrent outbreaks of food poisoning. Spores and biofilms are considered the most important reservoirs of B. cereus in contaminated fresh vegetables and fruits. Bacterial biofilms are difficult to eradicate specially due to the presence of a protective extracellular matrix made of exopolysaccharides, proteins, and other components. Amyloid-like proteins are essential for the integrity of biofilms of the related bacteria species Bacillus subtilis.
Objectives
To investigate the presence of amyloid-like fibers in biofilms of B. cereus.
Methods
We identified two genomic loci in B. cereus, which encode two orthologues of the amyloid-like protein TasA and a SipW signal peptidase of B. subtilis. Mutagenesis in B. cereus or heterologous expression of alleles in B. subtilis mutants combined with crystal violet staining served to evaluate the formation of biofilm. Electron microscopy let us visualize the presence of fibers on cells.
Conclusions
We demonstrate that the proteins TasA and CalY are necessary for B. cereus biofilm formation: i) as pellicle on the air-liquid interphase or ii) adhesion to abiotic surfaces. TasA and to a lesser extent CalY polymerizes in the form of fibers in the cell surface. Our findings of heterologous expression in B. subtilis let us propose an amyloid-like
FEMS-1178
Molecular principles of biofilm formation and dispersion
PSEUDOMONAS AERUGINOSA VIRULENCE FACTOR PYOCYANIN PROMOTES