Evolutionary history of the OmpR/IIIA family of signal transduction two component systems in Lactobacillaceae and Leuconostocaceae

<p>Abstract</p> <p>Background</p> <p>Two component systems (TCS) are signal transduction pathways which typically consist of a sensor histidine kinase (HK) and a response regulator (RR). In this study, we have analyzed the evolution of TCS of the OmpR/IIIA family in <it>Lactobacillaceae </it>and <it>Leuconostocaceae</it>, two families belonging to the group of lactic acid bacteria (LAB). LAB colonize nutrient-rich environments such as foodstuffs, plant materials and the gastrointestinal tract of animals thus driving the study of this group of both basic and applied interest.</p> <p>Results</p> <p>The genomes of 19 strains belonging to 16 different species have been analyzed. The number of TCS encoded by the strains considered in this study varied between 4 in <it>Lactobacillus helveticus </it>and 17 in <it>Lactobacillus casei</it>. The OmpR/IIIA family was the most prevalent in <it>Lactobacillaceae </it>accounting for 71% of the TCS present in this group. The phylogenetic analysis shows that no new TCS of this family has recently evolved in these <it>Lactobacillaceae </it>by either lineage-specific gene expansion or domain shuffling. Furthermore, no clear evidence of non-orthologous replacements of either RR or HK partners has been obtained, thus indicating that coevolution of cognate RR and HKs has been prevalent in <it>Lactobacillaceae</it>.</p> <p>Conclusions</p> <p>The results obtained suggest that vertical inheritance of TCS present in the last common ancestor and lineage-specific gene losses appear as the main evolutionary forces involved in their evolution in <it>Lactobacillaceae</it>, although some HGT events cannot be ruled out. This would agree with the genomic analyses of <it>Lactobacillales </it>which show that gene losses have been a major trend in the evolution of this group.</p

Regulation of bacteriocin production in Lactobacillus plantarum depends on a conserved promoter arrangement with consensus binding sequence

Bacteriocin production in Lactobacillus plantarum? C11 is regulated by a three-component signal transduction system comprising a peptide pheromone (PlnA), a histidine protein kinase (PlnB), and two homologous response regulators (RRs; PlnC and PlnD). Both RRs are DNA-binding proteins that bind to promoter-proximal elements in the pin regulon. The binding site for the two regulators consists of two 9-bp direct repeats, that conform to the consensus sequence 5 ' TACGTTAAT-3 '. and the repeats are separated by an intervening 12-bp AT-rich spacer region. In the present work, the plnA promoter was used as a model to evaluate the significance of the binding sequence and conserved promoter arrangement. Point substitutions in the consensus sequence, particularly those in invariant positions, either abolished or significantly reduced binding of PlnC and PlnD. Both regulators bind as homodimers to DNA fragments containing a complete set of regulatory elements, while removal of either repeat, or alterations in the length of the spacer region, significantly weakened binding of both protein dimers. DNase I footprinting demonstrated that PlnC and PlnD both bind to, and protect, the direct repeats. By fusing the plnA promoter region to the beta -glucuronidase (GUS) gene, it was shown that promoter activity is dependent on an intact set of accurately organized repeats. The in vitro and in vivo results presented here confirm the involvement of the repeats as regulatory elements in the regulation of bacteriocin production

Probiotics in Poultry

The main pathogens associated with poultry farming and production are various serotypes of Salmonella enterica, Escherichia coli and Campylobacter jejuni. Those enteric pathogens are the most common causes of diarrhea in the poultry flock in Indonesia. Their spread are due to poor sanitation and drainage as well as improper litter management, which all lead to bacterial infection in birds. Antibiotics have previously been used for many decades by veterinarians and poultry farmers before they were banned in many countries due to concerns with increased antibiotic resistance in pathogens and antibiotic contamination in food. In the search for an alternative to antibiotics in poultry feed, the addition of probiotics is proposed. Among all the probiotics utilized in poultry production, lactic acid bacteria (LAB) are the most commonly used. The addition of LAB replaces enteric pathogens by means of competitive exclusion in the poultry intestinal tract, thereby increasing the intestinal health of poultry. This chapter discusses the increased growth and performance of poultry due to the application of native LAB