Differentiation of Lactobacillus delbrueckii subspecies by ribotyping and amplified ribosomal DNA restriction analysis (ARDRA)

AIMS: To differentiate the subspecies of Lactobacillus delbrueckii, subsp. delbrueckii, subsp. lactis and subsp. bulgaricus. METHODS AND RESULTS: Amplified ribosomal DNA restriction analysis (ARDRA) and ribotyping were applied to over 30 strains. Both methods analyse the ribosomal genes which carry useful information about the evolutionary and taxonomic relationship among bacteria. The methods proved to be reliable and highly reproducible. ARDRA was applied to 16S rDNA, 23S rDNA and the IGS region, thus covering the whole rrn operon with eight restriction enzymes. Only EcoRI differentiated Lact. delbrueckii subsp. bulgaricus from Lact. delbrueckii subsp. delbrueckii/Lact. delbrueckii subsp. lactis, which confirmed the finding of other authors. Ribotyping with different enzymes under precisely optimized conditions revealed a high level of strain polymorphism. Only ribotyping with EcoRI allowed differentiation of the three subspecies on the basis of typical hybridization patterns. CONCLUSION: The successful differentiation of the three subspecies of Lact. delbrueckii by EcoRI ribotyping offers a new possibility for precise identification and differentiation of strains and new isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: Both methods could be used for differentiation of Lact. delbrueckii subspecies.     

Impact of methionine oxidation as an initial event on the pathway of human prion protein conversion

Prion diseases comprise a group of fatal neurodegenerative disorders characterized by the autocatalytic conversion of the cellular prion protein PrP^C into the infectious misfolded isoform PrP^Sc. Increasing evidence supports a specific role of oxidative stress in the onset of pathogenesis. Although the associated molecular mechanisms remain to be elucidated in detail, several studies currently suggest that methionine oxidation already detected in misfolded PrP^Sc destabilizes the native PrP fold as an early event in the conversion pathway. To obtain more insights about the specific impact of surface-exposed methionine residues on the oxidative-induced conversion of human PrP we designed, produced, and comparatively investigated two new pseudosulfoxidation mutants of human PrP 121–231 that comprises the well-folded C-terminal domain. Applying circular dichroism spectroscopy and dynamic light scattering techniques we showed that pseudosulfoxidation of all surface exposed Met residues formed a monomeric molten globule-like species with striking similarities to misfolding intermediates recently reported by other groups. However, individual pseudosulfoxidation at the polymorphic M129 site did not significantly contribute to the structural destabilization. Further metal-induced oxidation of the partly unfolded pseudosulfoxidation mutant resulted in the formation of an oligomeric state that shares a comparable size and stability with PrP oligomers detected after the application of different other triggers for structural conversion, indicating a generic misfolding pathway of PrP. The obtained results highlight the specific importance of methionine oxidation at surface exposed residues for PrP misfolding, strongly supporting the hypothesis that increased oxidative stress could be one causative event for sporadic prion diseases and other neurodegenerative disorders.     

Molecular identification of vaginal lactobacilli isolated from Bulgarian women

Lactobacilli play an important role in maintaining the vaginal health of women. The development of suitable bacterial replacement therapies for the treatment of vaginosis requires knowledge of the vaginal lactobacilli species representation. The aim of this study was to identify at the species level vaginal Lactobacillus isolates obtained from Bulgarian women in childbearing age by using different molecular methods. Twenty-two strains of lactobacilli isolated from vaginal samples were identified and grouped according to their genetic relatedness. A combined approach, which included amplified ribosomal DNA restriction analysis (ARDRA), ribotyping and polymerase chain reaction (PCR) with species-specific oligonucleotide primers was applied. All vaginal isolates were grouped into 5 clusters in␣comparison with a set of 21 reference strains based␣on the initial ARDRA results, which was then confirmed by ribotyping. Finally, the strains were subjected to PCR analysis with eight different species-specific primer pairs, which allowed most of␣them to be classified as belonging to one of␣the␣following species: Lactobacillus crispatus, Lactobacillus fermentum, Lactobacillus gasseri, Lactobacillus helveticus and Lactobacillus plantarum. In conclusion, this study suggests that the most straightforward identification strategy for vaginal lactobacilli would be grouping by ARDRA or ribotyping, followed by PCR specific primers identification at species level.     

An interaction between CD200 and monoclonal antibody agonists to CD200R2 in development of dendritic cells that preferentially induce populations of CD4+CD25+ T regulatory cells

In previous studies we reported that while interaction between the relatively ubiquitously expressed molecule CD200 and one of its receptors, CD200R1, resulted in direct suppression of alloreactivity, engagement of alternate receptors led instead to altered differentiation of dendritic cells (DCs) from marrow precursors, which could in turn foster development of Foxp3(+) regulatory T cells. We have explored this effect of engagement of alternate receptors by using a monoclonal agonist Ab to CD200R2 and investigating expression of TLRs on DCs induced in vivo and in vitro after CD200 stimulation in mice in which the gene encoding CD200R1 was deleted. CD200 stimulation was achieved by using either a soluble form of CD200 (CD200Fc) or overexpression of CD200 as a doxycycline-inducible transgene. Although broadly similar effects were seen, consistent with the hypothesis that triggering of CD200R2 does produce DCs with a characteristic TLR repertoire, there are subtle differences in suppression of alloreactivity achieved by CD200 delivered in these two manners, which is consistent with a complexity of CD200:CD200R engagement not previously appreciated.