Pheromone-induced expression of recombinant proteins in Streptococcus thermophilus

Abstract

A locus encoding proteins with high homology to the pneumococcal BlpABCHR quorum-sensing system was identified in Streptococcus thermophilus LMG 18311. The BlpABCHR system regulates bacteriocin production in Streptococcus pneumoniae by monitoring the extracellular concentration of a peptide-pheromone encoded by blpC. The homologous system in S. thermophilus, termed StbABCHR, contains a corresponding gene (stbC) encoding a possible peptide-pheromone (STP) that presumably controls bacteriocin production in S. thermophilus. We synthesized this peptide and found that it activates transcription of a gusA reporter gene placed behind the promoter of the bacteriocin-like gene stbD. Furthermore, deletion mapping and mutational analysis of the stbD promoter region were used to identify a degenerated direct repeat motif required for STP induced GusA expression. Our findings provide strong evidence that STP regulates bacteriocin production in S. thermophilus LMG 18311, and show that the StbABCHR quorum-sensing system can be exploited for inducible expression of recombinant proteins in this bacterial species.

Quorum-Sensing Regulation of the Production of Blp Bacteriocins in Streptococcus thermophilus

“…In agreement with this observation, transcriptome analyses suggest that BlpC St regulates the transcription of only genes located within the blp St locus of S. thermophilus LMD-9 (data not shown). In the course of the present study, Blomqvist et al (7) showed that a reporter fusion between the blpU St LMG18311 promoter and gusA was induced 10-fold by the predicted mature form of BlpC St LMG18311 in S. thermophilus LMG18311. These authors reported that the complete deletion of the DR motif from blpU St LMG18311 abolished the BlpC St -dependent induction of glucuronidase activity, further supporting the hypothesis that the DR motif is the binding site of BlpR St .…”

“…These authors reported that the complete deletion of the DR motif from blpU St LMG18311 abolished the BlpC St -dependent induction of glucuronidase activity, further supporting the hypothesis that the DR motif is the binding site of BlpR St . Additionally, various mutations in the left repeat, the right repeat, and the spacer of the DR motif affected induction of the promoter by BlpC St (7). In this context, the observed differences in the strength of the response to BlpC St among the DR-containing blp St operons blpD St -orf2, blpE-F St , blpU St -orf3, and blpABC St might result from different affinities of the regulatory protein BlpR St for the corresponding promoters as a consequence of mutations in the DR motif (Fig.…”

“…Electrotransformation of E. coli was performed as described by Dower et al (15). Electrocompetent S. thermophilus cells were prepared as previously described (7). After transformation with 1 g of plasmid DNA, cells were immediately resuspended in 1 ml of M17G medium and incubated anaerobically for 6 h at 37°C (pMG36e derivatives) or 29°C (pGhost9 derivatives).…”

Control of Competence for DNA Transformation in Streptococcus suis by Genetically Transferable Pherotypes

“…In the gut HGT and natural competence are likely to have played a major role in the evolution and ecology of the microbiota as well as strain diversity [8]. The competent state of “DNA receptivity” is controlled by a large, dispersed set of genes encoding proteins responsible for DNA uptake and recombination, as well as other processes related to competence induced cell stress [9], [10], [11], [12], [13], [14]. Homologues of competence genes are widespread among bacteria that have not yet been demonstrated to be naturally transformable, suggesting that the mechanism may in fact be more common, especially within the phyla that contain members that are already known to be naturally competent.…”

Streptococcus thermophilus, an emerging and promising tool for heterologous expression: Advantages and future trends

“…Thus, it has been shown that the luciferase of Photorhabdus luminescens (Fontaine et al, 2010aGardan et al, 2013) and the green fluorescent protein gene of the jellyfish Aequorea victoria (Solaiman and Somkuti, 1997a;Somkuti and Steinberg, 1999;Renye and Somkuti, 2009) were both functional in S. thermophilus. This is also the case for the gusA gene of E. coli which confers the b-glucuronidase activity (Mora et al, 2005;Blomqvist et al, 2006b;Liu et al, 2009;Chang and Yan, 2014) or the gene encoding the a-galactosidase of Lc.…”