RESUMEN
The probiotic product Symbioflor2 (DSM 17252) is a bacterial concentrate of six different Escherichia coli genotypes, whose complete genome sequences are compared here, between each other as well as to other E. coli genomes. The genome sequences of Symbioflor2 E. coli components contained a number of virulence-associated genes. Their presence seems to be in conflict with a recorded history of safe use, and with the observed low frequency of adverse effects over a period of more than 6 years. The genome sequences were used to identify unique sequences for each component, for which strain-specific hybridization probes were designed. A colonization study was conducted whereby five volunteers were exposed to an exceptionally high single dose. The results showed that the probiotic E. coli could be detected for 3 months or longer in their stools, and this was in particular the case for those components containing higher numbers of virulence-associated genes. Adverse effects from this long-term colonization were absent. Thus, the presence of the identified virulence genes does not result in a pathogenic phenotype in the genetic background of these probiotic E. coli.
RESUMEN
The complete genome of probiotic Escherichia coli strain G3/10 is presented here. In addition, the probiotic E. coli strains G1/2, G4/9, G5, G6/7, and G8 are presented in draft form. These six strains together comprise the probiotic product Symbioflor 2 (DSM 17252).
RESUMEN
BACKGROUND: Interleukin-10 homologues encoded by Herpes viruses such as Epstein-Barr virus (EBV) and human cytomegalovirus (HCMV) hold interesting structural and biological characteristics compared to human interleukin-10 (hIL-10) that render these proteins promising candidates for therapeutic application in inflammatory bowel disease (IBD). Intestinal delivery of cytokines using bacterial carriers as chassis represents a novel approach for treatment of IBD patients. For proof of concept, a Sec-dependent transporter construct was designed for secretory expression of recombinant viral IL-10 proteins in the periplasm of Escherichia coli laboratory strain BL21 (DE3), which might serve as part of a prospective lysis based delivery and containment system. RESULTS: The signal peptide of E. coli outer membrane protein F fused to the mature form of the viral IL-10 proteins enabled successful transport into the periplasm, a compartment which seems crucial for proper assembly of the dimeric configuration of the cytokines. Cytokine concentrations in different bacterial compartments were determined by ELISA and achieved yields of 67.8 ng/ml ± 24.9 ng/ml for HCMV IL-10 and 1.5 µg/ml ± 841.4 ng/ml for EBV IL-10 in the periplasm. Immunoblot analysis was used to confirm the correct size of the E. coli-derived recombinant cytokines. Phosphorylation of signal transducer and activator of transcription 3 (STAT3) as part of the signal transduction cascade after IL-10 receptor interaction, as well as suppression of tumor necrosis factor α (TNF-α) release of lipopolysaccharide-stimulated mouse macrophages were used as read-out assays for proving in vitro biological activity of the E. coli derived, recombinant viral IL-10 counterparts. CONCLUSIONS: In this study, proof of principle is provided that E. coli cells are a suitable chassis for secretory expression of viral IL-10 cytokines encoded by codon-optimized synthetic genes fused to the E. coli ompF signal sequence. In vitro biological activity evidenced by activation of transcription factor STAT3 and suppression of TNF-α in mammalian cell lines was shown to be strictly dependent on export of viral IL-10 proteins into the periplasmic compartment. E. coli might serve as carrier system for in situ delivery of therapeutic molecules in the gut, thus representing a further step in the development of novel approaches for treatment of IBD.
Asunto(s)
Citomegalovirus/genética , Herpesvirus Humano 4/genética , Interleucina-10/metabolismo , Proteínas Virales/metabolismo , Animales , Línea Celular , Escherichia coli/genética , Escherichia coli/metabolismo , Vectores Genéticos/genética , Humanos , Enfermedades Inflamatorias del Intestino/terapia , Interleucina-10/genética , Ratones , Periplasma/metabolismo , Fosforilación , Porinas/genética , Porinas/metabolismo , Señales de Clasificación de Proteína/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Factor de Transcripción STAT3/metabolismo , Análisis de Secuencia de ADN , Transducción de Señal , Factor de Necrosis Tumoral alfa/antagonistas & inhibidores , Proteínas Virales/genéticaRESUMEN
Escherichia coli G3/10 is a component of the probiotic drug Symbioflor 2. In an in vitro assay with human intestinal epithelial cells, E. coli G3/10 is capable of suppressing adherence of enteropathogenic E. coli E2348/69. In this study, we demonstrate that a completely novel class II microcin, produced by probiotic E. coli G3/10, is responsible for this behavior. We named this antibacterial peptide microcin S (MccS). Microcin S is coded on a 50.6 kb megaplasmid of E. coli G3/10, which we have completely sequenced and annotated. The microcin S operon is about 4.7 kb in size and is comprised of four genes. Subcloning of the genes and gene fragments followed by gene expression experiments enabled us to functionally characterize all members of this operon, and to clearly identify the nucleotide sequences encoding the microcin itself (mcsS), its transport apparatus and the gene mcsI conferring self immunity against microcin S. Overexpression of cloned mcsI antagonizes MccS activity, thus protecting indicator strain E. coli E2348/69 in the in vitro adherence assay. Moreover, growth of E. coli transformed with a plasmid containing mcsS under control of an araC PBAD activator-promoter is inhibited upon mcsS induction. Our data provide further mechanistic insight into the probiotic behavior of E. coli G3/10.
Asunto(s)
Antibacterianos/metabolismo , Bacteriocinas/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Péptidos/metabolismo , Probióticos/metabolismo , Secuencia de Aminoácidos , Adhesión Bacteriana/genética , Bacteriocinas/genética , Células CACO-2 , Línea Celular Tumoral , ADN Bacteriano/química , ADN Bacteriano/genética , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica , Orden Génico , Humanos , Viabilidad Microbiana/genética , Datos de Secuencia Molecular , Familia de Multigenes/genética , Operón/genética , Péptidos/genética , Plásmidos/genética , Análisis de Secuencia de ADNRESUMEN
Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine, with therapeutic applications in inflammatory bowel disease. For the in situ delivery of IL-10 by Escherichia coli as carrier chassis, a modified transporter was designed with the ability to secrete biologically active IL-10. De novo DNA synthesis comprised a 561-bp fragment encoding the signal sequence of the E. coli outer membrane protein F fused in frame to an E. coli codon-optimized mature human IL-10 gene under control of a T7 promoter. The construct was overexpressed in E. coli laboratory strains, E. coli BL21 (DE3) and E. coli MDS42:T7. The mean concentrations of human IL-10 in the periplasm and culture supernatant of E. coli BL21 (DE3) were 355.8 ± 86.3 and 5.7 ± 1.7 ng/ml, respectively. The molecular mass of the recombinant E. coli-derived human IL-10 was 19 kDa, while under non-reducing conditions the native IL-10 dimer could be demonstrated. Reduction of tumor necrosis factor-α secretion in lipopolysaccharide-stimulated mouse macrophages and detection of the activated form of the transcription factor signal transducer and activator of transcription protein 3 proved the biological activity of the bacteria-produced human IL-10.
