Cellular Injuries in CIP 103183T and Exposed to Drying and Subsequent Heat Treatment in Milk Powder.

Because of the ability of foodborne pathogens to survive in low-moisture foods, their decontamination is an important issue in food protection. This study aimed to clarify some of the cellular mechanisms involved in inactivation of foodborne pathogens after drying and subsequent heating. Individual strains of Typhimurium, Senftenberg, and were mixed into whole milk powder and dried to different water activity levels (0.

Caco-2 Invasion by and Exposed to Drying and Heat Treatments in Dried State in Milk Powder.

Due to the ability of foodborne pathogens to survive in low moisture food, the decontamination of milk powder is an important issue in food protection. The safety of food products is, however, not always insured and the different steps in the processing of food involve physiological and metabolic changes in bacteria. Among these changes, virulence properties may also be affected.

Drying parameters greatly affect the destruction of Cronobacter sakazakii and Salmonella Typhimurium in standard buffer and milk.

Salmonella Typhimurium and Cronobacter sakazakii are two foodborne pathogens involved in neonatal infections from milk powder and infant formula. Their ability to survive in low-moisture food and during processing from the decontamination to the dried state is a major issue in food protection. In this work, we studied the effects of the drying process on Salmonella Typhimurium and Cronobacter sakazakii, with the aim of identifying the drying parameters that could promote greater inactivation of these two foodborne pathogens.

Recovery Estimation of Dried Foodborne Pathogens Is Directly Related to Rehydration Kinetics.

Drying is a common process which is used to preserve food products and technological microorganisms, but which is deleterious for the cells. The aim of this study is to differentiate the effects of drying alone from the effects of the successive and necessary rehydration. Rehydration of dried bacteria is a critical step already studied in starter culture but not for different kinetics and not for pathogens.

A single mutation in the gene responsible for the mucoid phenotype of Bifidobacterium animalis subsp. lactis confers surface and functional characteristics.

Exopolysaccharides (EPS) are extracellular carbohydrate polymers synthesized by a large variety of bacteria. Their physiological functions have been extensively studied, but many of their roles have not yet been elucidated. We have sequenced the genomes of two isogenic strains of Bifidobacterium animalis subsp.

Sequence analysis of plasmid pSP02 from Bifidobacterium longum M62 and construction of pSP02-derived cloning vectors.

Replicons from bifidobacteria species are required for the construction of general- and special-purpose vectors that would allow the undertaking of molecular studies of these bacteria. In this work, pSP02, a cryptic plasmid from Bifidobacterium longum M62, was cloned, sequenced and characterized. pSP02 was found to consist of 4896bp with four ORFs coding for proteins over 50 amino acids long.

Genome sequence of the lantibiotic bacteriocin producer Streptococcus salivarius strain K12.

Streptococcus salivarius is a prevalent commensal species of the oropharyngeal tract. S. salivarius strain K12 is an isolate from the saliva of a healthy child, used as an oral probiotic.

A two-component regulatory system controls autoregulated serpin expression in Bifidobacterium breve UCC2003.

This work reports on the identification and molecular characterization of a two-component regulatory system (2CRS), encoded by serRK, which is believed to control the expression of the ser(2003) locus in Bifidobacterium breve UCC2003. The ser(2003) locus consists of two genes, Bbr_1319 (sagA) and Bbr_1320 (serU), which are predicted to encode a hypothetical membrane-associated protein and a serpin-like protein, respectively. The response regulator SerR was shown to bind to the promoter region of ser(2003), and the probable recognition sequence of SerR was determined by a combinatorial approach of in vitro site-directed mutagenesis coupled to transcriptional fusion and electrophoretic mobility shift assays (EMSAs).

A conserved two-component signal transduction system controls the response to phosphate starvation in Bifidobacterium breve UCC2003.

This work reports on the identification and molecular characterization of the two-component regulatory system (2CRS) PhoRP, which controls the response to inorganic phosphate (P(i)) starvation in Bifidobacterium breve UCC2003. The response regulator PhoP was shown to bind to the promoter region of pstSCAB, specifying a predicted P(i) transporter system, as well as that of phoU, which encodes a putative P(i)-responsive regulatory protein. This interaction is assumed to cause transcriptional modulation under conditions of P(i) limitation.

Controlled gene expression in bifidobacteria by use of a bile-responsive element.

The promoter activity of the upstream region of the bile-inducible gene betA from Bifidobacterium longum subsp. longum NCC2705 was characterized. DNA fragments were cloned into the reporter vector pMDYAbfB, and the arabinofuranosidase activity was determined under different in vitro conditions.

Candida cabralensis sp. nov., a yeast species isolated from traditional Spanish blue-veined Cabrales cheese.

Three yeast strains, 1AD8(T), 3AD15 and 3AD23, belonging to a previously unknown yeast species were isolated from two independent batches of the Spanish blue-veined Cabrales cheese, a traditional cheese manufactured without the addition of starter and mould cultures. Physiological characterization revealed that the unknown yeast is not fermentative and does not assimilate lactose; rather it assimilates dl-lactic acid and ethanol, major end products of lactic acid bacteria metabolism in cheese. The novel yeast is anamorphic.

Diversity and evolution of the microbial populations during manufacture and ripening of Casín, a traditional Spanish, starter-free cheese made from cow's milk.

Classical culturing and denaturing gradient gel electrophoresis (DGGE) techniques have been used for studying the microbial diversity and dynamics of the traditional Spanish Casín cheese during manufacturing and ripening. As with other starter-free cheeses made from raw milk, the microbial diversity of Casín was shown to be high by both culturing and DGGE analyses. The culture technique showed that lactic acid bacteria (LAB) species constituted the majority of the microbial populations.

Analysis of tetracycline resistance tet(W) genes and their flanking sequences in intestinal Bifidobacterium species.

Objectives: The tet(W) gene provides tetracycline resistance to a wide range of anaerobic intestinal and ruminal bacteria, but little is known about the molecular organization of the tet(W) gene. The aim of this study was to gain new insights into the molecular organization of the tet(W) gene in bifidobacteria strains from humans.

Methods: A segment of DNA encompassing the whole tet(W) gene and its immediate upstream and downstream sequences was analysed in 10 representative strains of four Bifidobacterium species, of which two have been shown to be tetracycline-susceptible.

Improved cloning vectors for bifidobacteria, based on the Bifidobacterium catenulatum pBC1 replicon.

This study reports the development of several cloning vectors for bifidobacteria based on the replicon of pBC1, a cryptic plasmid from Bifidobacterium catenulatum L48 thought to replicate via the theta mode. These vectors, in which antibiotic resistance genes encoding either erythromycin or tetracycline resistance acted as selection markers, were able to replicate in a series of eight Bifidobacterium species at frequencies ranging from 4.0 x 10(1) to 1.

Functional analysis of the pBC1 replicon from Bifidobacterium catenulatum L48.

To determine the minimal replicon of pBC1 (a 2.5-kb cryptic plasmid of Bifidobacterium catenulatum L48) and to check the functionality of its identified open reading frames (ORFs) and surrounding sequences, different segments of pBC1 were amplified by polymerase chain reaction (PCR) and cloned into pBif, a replication probe vector for bifidobacteria. The largest fragment tested in this manner encompassed most of the pBC1 sequence, while the shortest just included the repB gene and its immediate upstream sequences.

Acquired macrolide resistance in the human intestinal strain Lactobacillus rhamnosus E41 associated with a transition mutation in 23S rRNA genes.

Restriction fragment length polymorphism and DNA sequencing of polymerase chain reaction (PCR) products showed that a Lactobacillus rhamnosus strain of human origin resistant to macrolides, from which no resistance determinants have been detected by specific PCR and microarray screening, contained a heterozygous A-->G transition mutation at position 2058 (Escherichia coli numbering) of its 23S rRNA genes.

Reagentless identification of human bifidobacteria by intrinsic fluorescence.

A new identification method for bifidobacteria species from the human gastrointestinal tract was developed based on the measurement and statistical analysis of the intrinsic fluorescence of aromatic amino acids (AAA) and nucleic acids (NA), following their excitation at 250 nm. The model was constructed by recording the fluorescence spectra of 53 Bifidobacterium strains of 10 different species, including the corresponding type strains, and validated by analyzing the spectra data from nine further problem strains. Principal components analysis (PCA) and factorial discriminant analysis (FDA) of the results showed the technique to distinguish between the isolates at the species level; the Bifidobacterium pseudolongum subspecies (globosum and pseudolongum) could also be distinguished.

Molecular analysis of tet(W) gene-mediated tetracycline resistance in dominant intestinal Bifidobacterium species from healthy humans.

tet(W) was found responsible for tetracycline resistance (MICs, 4 to > or =32 microg ml(-1)) in dominant bifidobacterial species from the gastrointestinal tracts of healthy humans. The gene from Bifidobacterium longum H66 proved to be identical over a 2.6-kbp region to the recently described tet(W) determinant of Butyrivibrio fibrisolvens.

Screening for plasmids among human bifidobacteria species: sequencing and analysis of pBC1 from Bifidobacterium catenulatum L48.

Analysis of 72 bifidobacterial isolates for plasmid DNA identified six different plasmid profiles, two profiles consisted of a single plasmid and four contained at least two. A plasmid identified in a Bifidobacterium catenulatum strain (pBC1) was chosen for further characterization based on its small size and stability. The plasmid was shown to be a circular molecule of 2540 base pairs with an overall G+C content of 64%.