Bacteriocins are ribosomally synthesized antimicrobial peptides produced by bacteria, which have the ability to kill or inhibit other bacteria. Many bacteriocins are produced by food grade lactic acid bacteria (LAB). Indeed, the prototypic bacteriocin, nisin, is produced by Lactococcus lactis, and is licensed in over 50 countries. With consumers becoming more concerned about the levels of chemical preservatives present in food, bacteriocins offer an alternative, more natural approach, while ensuring both food safety and product shelf life. Bacteriocins also show additive/synergistic effects when used in combination with other treatments, such as heating, high pressure, organic compounds, and as part of food packaging. These features are particularly attractive from the perspective of controlling sporeforming bacteria. Bacterial spores are common contaminants of food products, and their outgrowth may cause food spoilage or food-borne illness. They are of particular concern to the food industry due to their thermal and chemical resistance in their dormant state. However, when spores germinate they lose the majority of their resistance traits, making them susceptible to a variety of food processing treatments. Bacteriocins represent one potential treatment as they may inhibit spores in the post-germination/outgrowth phase of the spore cycle. Spore eradication and control in food is critical, as they are able to spoil and in certain cases compromise the safety of food by producing dangerous toxins. Thus, understanding the mechanisms by which bacteriocins exert their sporostatic/sporicidal activity against bacterial spores will ultimately facilitate their optimal use in food. This review will focus on the use of bacteriocins alone, or in combination with other innovative processing methods to control spores in food, the current knowledge and gaps therein with regard to bacteriocin-spore interactions and discuss future research approaches to enable spores to be more effectively targeted by bacteriocins in food settings.

No abstract

The majority of the activation potential of the Saccharomyces cerevisiae TDH3 gene promoter is contained within nucleotides -676 to -381 (relative to the translation initiation codon). An upstream activation sequence (UAS) in this region has been characterized by in vitro and in vivo assays and demonstrated to be composed of two small, adjacent DNA sequence elements. The essential determinant of this upstream UAS is a general regulatory factor 1 (GRF1) binding site at nucleotides -513 to -501. A synthetic DNA element comprising this sequence, or an analogue in which two of the degenerate nucleotides of the GRF1 site consensus sequence were altered, activated 5' deleted TDH3 and CYC1 promoters. The second DNA element of the UAS is a 7 bp sequence which is conserved in the promoters of several yeast genes encoding glycolytic enzymes and occurs at positions -486 to -480 of the TDH3 promoter. This DNA sequence represents a novel promoter element: it contains no UAS activity itself, yet potentiates the activity of a GRF1 UAS. The potentiation of the GRF1 UAS by this element occurs when placed upstream from the TATA box of either the TDH3 or CYC1 promoters. The characteristics of this element (termed GPE for GRF1 site potentiator element) indicate that it represents a binding site for a different yeast protein which increases the promoter activation mediated by the GRF1 protein. Site-specific deletion and promoter reconstruction experiments suggest that the entire activation potential of the -676 to -381 region of the TDH3 gene promoter may be accounted for by a combination of the GRF1 site and the GPE.

The thermophilic, endospore-forming genus of Geobacillus has historically been associated with spoilage of canned food. However, in recent years it has become the subject of much attention due its biotechnological potential in areas such as enzyme and biofuel applications. One aspect of this genus that has not been fully explored or realized is its use as a source of novel forms of the ribosomally synthesized antimicrobial peptides known as bacteriocins. To date only two bacteriocins have been fully characterized within this genus, i.e., Geobacillin I and II, with only a small number of others partially characterized. Here we bioinformatically investigate the potential of this genus as a source of novel bacteriocins through the use of the in silico screening software BAGEL3, which scans publically available genomes for potential bacteriocin gene clusters. In this study we examined the association of bacteriocin gene presence with niche and phylogenetic position within the genus. We also identified a number of candidates from multiple bacteriocin classes which may be promising antimicrobial candidates when investigated in vitro in future studies.

Conditions for high-cell-density fermentations of Saccharomyces cerevisiae strains producing recombinant-DNA-derived proteins were established. Strains producing human immune interferon (IFN-gamma) from the constitutive PGK promoter failed to grow to high cell densities and exhibited low plasmid stability. Regulated expression of IFN-gamma was obtained in similar strains by employing a hybrid yeast GPD promoter that was subject to carbon source regulation due to the presence of regulatory DNA sequences from the yeast GAL 1,10 intergenic region. IFN-gamma expression programmed by this vector was low during growth on glucose and was induced by galactose. Previously defined fermentation conditions employing glucose as a carbon source were applied to this strain, resulting in high ceil densities with higher plasmid stability. Various methods of galactose induction of IFN-gamma expression in high-cell-density fermentations were investigated. Optimal conditions resulted in a 2000-fold induction and production of 2 g IFN-gamma/L fermentation culture.