In silico analysis highlights the frequency and diversity of type 1 lantibiotic gene clusters in genome sequenced bacteria.

Background: Lantibiotics are lanthionine-containing, post-translationally modified antimicrobial peptides. These peptides have significant, but largely untapped, potential as preservatives and chemotherapeutic agents. Type 1 lantibiotics are those in which lanthionine residues are introduced into the structural peptide (LanA) through the activity of separate lanthionine dehydratase (LanB) and lanthionine synthetase (LanC) enzymes.

Invited review: Lactobacillus helveticus--a thermophilic dairy starter related to gut bacteria.

The strain Lactobacillus helveticus DPC4571 has emerged as a promising flavor adjunct culture for Cheddar cheese given that it is consistently associated with improved flavor. The availability of the complete genome sequence of Lb. helveticus DPC4571 has enabled the search for the presence or absence of specific genes on the genome, in particular those of technological interest.

Effect of exopolysaccharide produced by isogenic strains of Lactococcus lactis on half-fat Cheddar cheese.

Fat-reduced cheeses often suffer from undesirable texture, flavor, and cooking properties. Exopolysaccharides (EPS) produced by starter strains have been proposed as a mechanism to increase yield and to improve the texture and cooking properties of reduced-fat cheeses. The objective of this work was to assess the influence of an exopolysaccharide on the yield, texture, cooking properties, and quality of half-fat Cheddar cheese.

Use of viability staining in combination with flow cytometry for rapid viability assessment of Lactobacillus rhamnosus GG in complex protein matrices.

The aim of this study was to demonstrate that flow cytometry (FACS) could potentially be employed for rapid viability assessment of probiotic bacteria immobilized or encapsulated in complex matrices. Lactobacillus rhamnosus GG was immobilized within six different protein environments using whey protein isolate (WPI) and yoghurt matrices and encapsulated within protein micro-beads, all of which ranged in structural complexity. Following a series of environmental-stress trials, survival of the strain was examined using FACS compared to traditional plate count techniques.

Effect of broad- and narrow-spectrum antimicrobials on Clostridium difficile and microbial diversity in a model of the distal colon.

Vancomycin, metronidazole, and the bacteriocin lacticin 3147 are active against a wide range of bacterial species, including Clostridium difficile. We demonstrate that, in a human distal colon model, the addition of each of the three antimicrobials resulted in a significant decrease in numbers of C. difficile.

A new cryo-STEM method for imaging food colloids in the scanning electron microscope.

A new cryo-scanning transmission electron microscopy (cryo-STEM) technique for imaging casein micelles in a field emission scanning electron microscope is presented. Thin films of micellar casein suspensions on lacey carbon grids were prepared using a modified sample holder developed by Gatan UK. Bright and dark field images were obtained at -135°C showing casein micelles in their frozen hydrated state and in the size range 30-500 nm.

Synthesis of trypsin-resistant variants of the Listeria-active bacteriocin salivaricin P.

Two-component salivaricin P-like bacteriocins have demonstrated potential as antimicrobials capable of controlling infections in the gastrointestinal tract (GIT). The anti-Listeria activity of salivaricin P is optimal when the individual peptides Sln1 and Sln2 are added in succession at a 1:1 ratio. However, as degradation by digestive proteases may compromise the functionality of these peptides within the GIT, we investigated the potential to create salivaricin variants with enhanced resistance to the intestinal protease trypsin.

The food glycome: a source of protection against pathogen colonization in the gastrointestinal tract.

Trillions of microbes inhabit the gastrointestinal tract of humans with significant differences in the composition and distribution of intestinal flora along its length. Normally there is a symbiotic relationship between the intestinal microflora and the host, with mutual advantages for both partners. When this relationship is altered, commensal bacteria can rapidly shift toward pathogenicity resulting in the onset and progression of gastrointestinal infection.

Nutrient regulation of enteroendocrine cellular activity linked to cholecystokinin gene expression and secretion.

The hormone cholecystokinin is produced by the enteroendocrine I cells in the intestine, and it plays an important role in a number of physiological processes including digestion and food intake. Recent data suggest that cholecystokinin gene expression and protein secretion are regulated by macronutrients. The mechanism involves a change in intracellular levels of cAMP and Ca(+2), brought about by the activity of a number of nutrient-responsive G protein-coupled receptors, nutrient transporters, ion channels and intracellular enzymes.

Genome analysis of the Clostridium difficile phage PhiCD6356, a temperate phage of the Siphoviridae family.

The temperate phages PhiCD6356 and PhiCD6365 were isolated and characterised following mitomycin C induction of 43 Clostridium difficile strains. Both phages belong to the Siphoviridae family and have genome sizes of 37,664 bp for PhiCD6356 based on sequence data and approximately 50 kb for PhiCD6365 based on restriction analysis. Protein analysis revealed similar protein profiles and indicated posttranslational processing of the PhiCD6356 major capsid protein.

Thuricin CD, a posttranslationally modified bacteriocin with a narrow spectrum of activity against Clostridium difficile.

The last decade has seen numerous outbreaks of Clostridium difficile-associated disease (CDAD), which presented significant challenges for healthcare facilities worldwide. We have identified and purified thuricin CD, a two-component antimicrobial that shows activity against C. difficile in the nanomolar range.

Comparison between red-green-blue imaging and visible-near infrared reflectance as potential process analytical tools for monitoring syneresis.

The current work focuses on the comparison of 2 on-line optical sensing systems; namely red-green-blue imaging and visible-near infrared reflectance, for monitoring syneresis during cheese manufacture. The experimental design consisted of 3 temperature treatments carried out in an 11-L cheese vat in triplicate. Both systems were shown to predict syneresis without significant differences in prediction accuracy.

Effect of denaturation of alpha-lactalbumin on the formation of BAMLET (bovine alpha-lactalbumin made lethal to tumor cells).

A complex of alpha-lactalbumin with oleic acid, also known as HAMLET/BAMLET (human/bovine alpha-lactalbumin made lethal to tumor cells), causes apoptosis-like death in tumor cells but has little effect on healthy differentiated cells. The aim of this study was to examine whether irreversible denaturation of alpha-lactalbumin is detrimental to the formation and cytotoxicity of BAMLET. Commercial bovine holo alpha-lactalbumin (1-4% w/v) was heated at 80 degrees C for up to 100 min.

Characterization of beta-lactoglobulin fibrillar assembly using atomic force microscopy, polyacrylamide gel electrophoresis, and in situ fourier transform infrared spectroscopy.

The aggregation process of beta-lactoglobulin (beta-lg) from 0 min to 20 h was studied using atomic force microscopy (AFM), scanning transmission electron microscopy (STEM), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and in situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Fibril assembly was monitored in real time using AFM up to 20 h. From 0 to 85 min, beta-lg monomers deformed and expanded with some aggregation.

Polymorphisms in the bovine lactoferrin promoter are associated with reproductive performance and somatic cell count.

Lactoferrin plays an important role in the innate immune system, with well-characterized antibacterial, antiviral, and immune modulatory properties. The objective of this study was to determine the allele and haplotype frequency of polymorphisms at positions -586, -190, and -28 of the bovine lactoferrin promoter in Holstein-Friesians and to quantify their association with performance using phenotypic data on progeny from 848 sires. Associations between genotypes and performance were quantified using weighted mixed models with genotyped individuals included as a random effect, and average expected relationships among individuals accounted for through a numerator relationship matrix.

Efficacy of whey protein gel networks as potential viability-enhancing scaffolds for cell immobilization of Lactobacillus rhamnosus GG.

This study investigated cell immobilization of Lactobacillus rhamnosus GG in three separate protein products: native, denatured and hydrolysed whey protein isolate (WPI). Treatments were assessed for their ability to enhance probiotic survival during storage, heat stress and ex vivo gastric incubation. Spatial distribution of probiotic cells within immobilized treatments was evaluated by atomic force and confocal scanning laser microscopy, while cell viability was enumerated by plate count and flow cytometry (FACS).

Association of beta-glucan endogenous production with increased stress tolerance of intestinal lactobacilli.

The exopolysaccharide beta-glucan has been reported to be associated with many health-promoting and prebiotic properties. The membrane-associated glycosyltransferase enzyme (encoded by the gtf gene), responsible for microbial beta-glucan production, catalyzes the conversion of sugar nucleotides into beta-glucan. In this study, the gtf gene from Pediococcus parvulus 2.

Crucial role for insertion sequence elements in Lactobacillus helveticus evolution as revealed by interstrain genomic comparison.

Lactobacillus helveticus is a versatile dairy bacterium found to possess heterogeneous genotypes depending on the ecosystem from which it was isolated. The recently published genome sequence showed the remarkable flexibility of its structure, demonstrated by a substantial level of insertion sequence (IS) element expansion in association with massive gene decay. To assess this diversity and examine the level of genome plasticity within the L.

Validation of a curd-syneresis sensor over a range of milk composition and process parameters.

An online visible-near-infrared sensor was used to monitor the course of syneresis during cheesemaking with the purpose of validating syneresis indices obtained using partial least squares, with cross-validation across a range of milk fat levels, gel firmness levels at cutting, curd cutting programs, stirring speeds, milk protein levels, and fat:protein ratio levels. Three series of trials were carried out in an 11-L cheese vat using recombined whole milk. Three factorial experimental designs were used, consisting of 1) 3 curd stirring speeds and 3 cutting programs; 2) 3 milk fat levels and 3 gel firmness levels at cutting; and 3) 2 milk protein levels and 3 fat:protein ratio levels, respectively.

Occurrence of foodborne pathogens in Irish farmhouse cheese.

Food safety is a critical factor in the production of farmhouse cheese. In Ireland the varieties of farmhouse cheese produced reflect a much broader range than those produced commercially and some of these cheese varieties are associated with greater microbiological risk. These include cheese produced from unpasteurised milk and soft ripened cheese such as mould or smear-ripened cheeses which have high pH and relatively short ripening times.

Reconstitution conditions for dried probiotic powders represent a critical step in determining cell viability.

Aims: Resuscitation of dried cultures represents a critical control point in obtaining active and effective probiotic strains. This study examined the effects of various rehydration conditions on the viability of Bifidobacterium longum NCC3001 and Lactobacillus johnsonii La1.

Methods And Results: Reconstitution conditions for these strains were optimized using a multivariate experimental design approach.

Efficacy of a teat dip containing the bacteriocin lacticin 3147 to eliminate Gram-positive pathogens associated with bovine mastitis.

On most dairy farms teat dips are applied to the teats of cows either before or after milking in order to prevent pathogens from gaining access to the mammary gland via the teat canal. In the present experiments, a natural teat dip was developed using a fermentate containing the live bacterium Lactococcus lactis DPC 3251. This bacterium produces lacticin 3147, a two-component lantibiotic which was previously shown to effectively kill Gram-positive mastitis pathogens.

Genome of a virulent bacteriophage Lb338-1 that lyses the probiotic Lactobacillus paracasei cheese strain.

There is a lack of fundamental knowledge about the influence of bacteriophage on probiotic bacteria and other commensals in the gut. Here, we present the isolation and morphological and genetic characterization of a virulent narrow-host-range bacteriophage, phiLb338-1. This phage was isolated from fresh sewage and was shown to infect the probiotic cheese strain Lactobacillus paracasei NFBC 338.

CRISPR analysis of bacteriophage-insensitive mutants (BIMs) of industrial Streptococcus thermophilus--implications for starter design.

Aims: An efficient approach for generation of bacteriophage-insensitive mutants (BIMs) of Streptococcus thermophilus starters was described in our laboratory [Mills et al. (2007) J Microbiol Methods70, 159-164]. The aim of this study was to analyse the phage resistance mechanism responsible for BIM formation.

Listeria monocytogenes in the Irish dairy farm environment.

Listeria monocytogenes is a potentially lethal foodborne pathogen commonly found in the environment. European Union hygiene legislation places responsibility for safety on primary production facilities, including farms, as part of a policy to introduce traceability throughout the food chain. This study aimed to determine the occurrence of L.