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Salmonella enterica serovar infection is a major cause of gastroenteritis and the use of probiotics offers the potential to improve the situation. The effects of oral treatment of pigs with a defined lactic acid bacteria culture mixture on both clinical and microbiological signs of Salmonella enterica serovar Typhimurium infection are investigated.

Lacticin 3147 is a broad-spectrum two-peptide lantibiotic whose genetic determinants are located on two divergent operons on the lactococcal plasmid pMRC01. Each of 14 subclones were introduced containing different combinations of lacticin 3147 genes into MG1363 (pMRC01) and determine that a number of them can facilitate overproduction of the lantibiotic.

An observation about SigB that contributes positively to Listeria monocytogenes tolerance of the bacteriocins nisin and lacticin 3147 and of the antibiotics ampicillin and penicillin G. is presented. The results showed that SigB might contribute to the survival of Listeria monocytogenes both in the food-processing environment and in vivo during infection which might represent an attractive target for the development of new control and treatment strategies for this important pathogen.

The performance of orally administered Lactobacillus mutinus in the pigs of five cultures is studied for determining its ability to survive, predominate and persist in the porcine gastrointestinal tract. A strong basis for exploring the potential of porcine-derived isolates as probiotic feed additives for pigs is provided and further studies are necessary for characterizing their in vivo efficacy.

This article describes a method to create gene knockouts and/or replacements on native plasmids without changing the food-grade status of the native plasmid in Lactococcus lactis. The procedure employs a temperature-sensitive RepA(sup)+ plasmid and a RepA(sup)- cloning vector.

Researchers have discovered a genetic sequence on the lactococcal plasmid pMRC01 that resembles an origin of transfer (oriT). This oriT could be used to in a vector to genetically modify lactococcal starter strains used in the food industry.

Researchers have succeeded in creating a strain of Lactobacillus paracasei subsp. paracasei that is highly resistant to lacticin 3147. Lacticin 3147 is a bacteriocin that can be used to inhibit nonstarter lactic acid bacteria in cheese cultures. Thus, the resistant strain will survive during cheese ripening whereas the nonstarter lactic acid bacteria will not.

Researchers describe a bacteriophage resistance plasmid that could be used to improve bacterial strains used in industrial dairy fermentations. It coes for phage defense systems and can be linked to a food-grade marker on a lactococci replicon.

The relationship between lysis and lysogeny in Lactococcus lactis in cheese has been studied using prophage-targeting PCR. Findings indicate the contribution of prophage to starter cell lysis and the potential of PCR as a useful starting screen to assess strains for the important industrial trait, the lytic behavior of lactococcal starter strains, which significantly correlates with the presence of prophage sequences.

The plasmid-free Lactococcus lactis subsp. cremoris MG1614 is highly sensitive to bacteriophages and does not have fermenting (Lac) and primary casein degrading (Prt) abilities. This strain was used with food grade gene transfer systems to sequentially superimpose various phage resistance mechanisms. The introduction of pLP712, which encodes Lac and Prt, into these hosts, which have plasmids encoding adsorption inhibition, restriction modification, and abortive infection, produced a phage-resistant strain which was successfully used as a single-strain starter for cheddar cheese production.

The effectiveness of a teat seal containing the novel bacteriocin lacticin 3147 in inhibiting mastitis pathogens in vitro was investigated. Molten brain heart infusion agar was seeded with an overnight culture of each streptococcal strain or staphylococcal strain to determine the sensitivity of either strain to lacticin 3147. Results showed that the teat seal displayed excellent antimicrobial activity, indicating the potential of lacticin 3147 to prevent mastitis.

Partial purification by chromatography was used to characterize lacticin 3147, a bacteriocin produced by Lactococcus lactis. Results revealed that two components of the bacteriocin are required for full activity. The bacteriocin was bactericidal against L. lactis, Listeria monocytogenes and Bacillus subtilis, while bactericidal activity was enhanced when target cells were energized. These suggested that the presence of a proton motive force promotes the interaction of lacticin 3147 with the cytoplasmic membrane.

The conjugative 63-kb lactococcal plasmid pMRC01 was transferred into several lactococcal starter cultures to enhance their phage resistance characteristics. Findings showed that efficient transfer of the plasmid is dependent on the particular recipient strain selected. Also, while there was high frequency transfer of the entire plasmid to some strains, the plasmid could not be conjugated into a number of starters.

Lactococcus lactis subsp. DPC4268 containing the plasmid encoding the bacteriocin lacticin 3147 is an effective starter for the formation of cheddar cheese. L. lactis produces acid and suppresses nisin-producing lactic acid bacteria in manner similar to that of commercially used cheese starting strains. Lacticin 3147 is heat stable specially at low pHs. Lacticin 3147 is not a homolog of nisin as the nisin structural gene probe does not hybridize with L. lactis 3147 DNA.

A new, nonmobilizable plasmid in Lactococcus lactis subsp. lactis biovar diacetylactis DPC938 produces the bacteriocins lactococcins A, B, and M, which appear to have bacteriolytic activity. The DNA encoding the bacteriocins in DPC938 was shown to be highly similar that in strains 9B4 and DPC3286. Lysis was indicated by the release of intracellular enzymes and a decrease in optical density and viable count. These lytic effects may be useful in accelerating cheese ripening.

The effect of bacteriophages (phages) e11/2 and e4/1c against Escherichia coli O157:H7 is examined in an ex vivo rumen model and in cattle in vivo. Ex vivo studies have shown that the phages are effective against Escherichia coli O157:H7 in a model rumen system, but complete eradication of Escherichia coli O157:H7 from cattle is not achieved.

The analysis of a complete set of glutamate decarboxylase (gad) mutants of Listeria monocytogenes strain LO28 has shown that the [DELTA]gadD1 mutant is impaired in its ability to tolerate exposure to both sublethal and lethal levels of the lantibiotic nisin. The studies have shown that the specific inhibition of GAD activity or a reduction in the levels of free glutamate has prevented the growth of otherwise resistant [GAD.sup.+] bacteria in foods where low pH and/or nisin is used as a preservative.

A study was conducted demonstrate the potential of two-component salivaricin P-like bacteriocins as antimicrobials to control infections in the gastrointestinal tract (GIT). The results demonstrated the potential of engineering bacteriocin variants which exhibit resistance to specific protease action but retain significant antimicrobial activity.

The pediococcal glycosyltransferase gene (gtf) is heterologously expressed that is responsible for the synthesis and secretion of the 2 substituted (1,3) beta-D-glucans in Lactobacillus paracasei NFBC 338. The results have shown that the production of a beta-glucan exopolysaccharide by strains destined for use as probiotics have provided them greater performance during cultivation, processing and ingestion.

The genomes of nine strains of Lactobacillus helveticus isolated from the diary environment are compared and studied. The analysis of the insertion sequence (IS)-flanked clusters has shown that the most frequently encountered ISs are also most abundant in the genome, which have contributed to the versatile character of IS elements and the role they might play in bacterial genome plasticity.

The highly conserved nature of lantibiotic biosynthetic enzymes is used for screening publicly available microbial genome sequences for genes encoding LanM proteins, which are needed for the posttranslational modification of type 2 lantibiotics. The Bacillus licheniformis strain is selected for a proof-of-concept exercise, which has established that a two-peptide lantibiotic, lichenicidin, is indeed produced, thereby confirming the benefits of such a bioinformatic approach when screening for novel lantibiotic producers.

A truncated derivative of the phage endolysin LysK containing only the CHAP (cysteine- and histidine-dependent amidoydrolase/peptidase) domain that exhibited lytic activity against live clinical staphylococcal isolates, including methicillin-resistant Staphylococcus aureus is reported. This is the first example of truncated phage lysin that has retained high lytic activity against live staphylococcal cells.

The component peptides of lacticin 3147 are degraded by using [alpha]-chymotrypsin in vitro with a resultant loss of antimicrobial activity in ileum digesta. The findings have shown that lacticin 3147 ingestion does not have adverse effects as it is inactivated during intestinal transit.

The identification of genetic loci involved in lantibiotic resistance development is discussed. The creation of two mutants by nonpolar deletions resulted in stable food-grade strains with increased resistance to both lactin 3147 and nisin.

Lactobacillus salivarius is a porcine intestinal isolate, which produces a two-component bacteriocin, salivaricin P., produced by a human probiotic L. salivarius strain. The production of such two-component antilisterial bacteriocins is found to be a very common feature among the mammalian intestinal L. salivarius strains.

The potential of using the lactococcal Mg2+ and Co2+ transport orf18/corA provides as a tool for genetic manipulation of lactococci to eliminate background resistances when they are used in conjunction with another marker are investigated. It is observed that overexpression of orf18/corA resulted in cell growth inhibition on certain concentrations of CoCl2.

The geneti c determinants for lactose utilization from lactobacillus delbrueckii subsp. bulgaricus ATCC 11842 and galactose utilization from lactococcus lactis subsp. cremoris MG 1363 are heterologously expressed in the lysine-overproducing strain corynebacterium glutamicum ATCC 21253. The findings indicate that growth and lysine production by C.glutamicum 21253 in whey-based media is extremely slow and inefficient.

The possibility of exploiting lytic enzyme enterolysin A(EntL) in applications involving lactococcal starter cultures is investigated. A recombinant lactococcal strain is generated which expresses EntL under the control of the nisin-inducible promoter and consequently allows nisin-induced autolysis.

Research shows that the fluctuating levels of bacteriocin production by Lactobacillus lactis DPC4275 is linked to an 80-kilobase cointegrate plasmid formed by the incorporation of the lacticin 3147 genes into the bacterial plasmid. The pheotypic traits of this plasmid transconjugant are discussed.

Research has been conducted on transconjugant lactococcal starters producing lantibiotics lacticin 3147 and lacticin 481. Results demonstrate that these starters have been generated via bacteriocin-encoding plasmid conjugation.