Paenibacillus larvae enolase as a virulence factor in honeybee larvae infection.
ABSTRACT Paenibacillus larvae is a gram-positive spore-forming bacteria, causative agent of American Foulbrood (AFB), a severe disease affecting larvae of the honeybee Apis mellifera. In an attempt to detect potential virulence factors secreted by P. larvae, we identified an enolase among different secreted proteins. Although this protein is a cytosolic enzyme involved in glycolytic pathways, it has been related to virulence. The aim of the present work was to evaluate its role during the infection of honeybee larvae. Toxicity assays showed that enolase was highly toxic and immunogenic to honeybee larvae. Its production was detected inside P. larvae vegetative cells, on the surface of P. larvae spores and secreted to the external growth medium. P. larvae enolase production was also confirmed in vivo, during the infection of honeybee larvae. This protein was able to hydrolyze milk proteins as described for P. larvae, suggesting that could be involved in larval degradation, maybe through the plasmin(ogen) system. These results suggest that P. larvae enolase may have a role in virulence and could contribute to a general insight about insect-pathogen interaction mechanisms.
- SourceAvailable from: Martin I ChilversApplications in plant sciences. 01/2013; 1(1).
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ABSTRACT: The spore forming bacterium Paenibacillus larvae causes a severe and highly infective bee disease, American Foulbrood (AFB). Despite the large economic losses induced by AFB, the virulence factors produced by P. larvae are as yet unknown. To identify such virulence factors, we experimentally infected young, susceptible larvae of the honeybee, Apis mellifera carnica, with different P. larvae isolates. Honeybee larvae were reared in vitro in 24-well plates in the laboratory after isolation from the brood comb. We identified genotype-specific differences in the etiopathology of AFB between the tested isolates of P. larvae, which were revealed by differences in the LT100. We furthermore confirmed that extracts of P. larvae cultures contain low molecular weight compounds, which are toxic to honeybee larvae. Our data indicate that P. larvae secretes metabolites into the medium with a potent honeybee toxic activity pointing to a novel pathogenic factor(s) of P. larvae. Genome mining of P. larvae ssp. larvae BRL-230010 led to the identification of several biosynthesis gene clusters putatively involved in natural product biosynthesis highlighting the potential of P. larvae to produce such compounds.Applied and Environmental Microbiology 02/2014; · 3.95 Impact Factor
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ABSTRACT: The bacterium Paenibacillus larvae has been extensively studied as it is an appalling honey bee pathogen. In the present work, we screened crude extracts derived from fermentations of P. larvae genotypes ERIC I and II for antimicrobial activity, following the detection of four putative secondary metabolite gene clusters that show high sequence homology to known biosynthetic gene clusters for the biosynthesis of antibiotics. Low molecular weight metabolites produced by P. larvae have recently been shown to have toxic effects on honey bee larvae. Moreover, a novel tripeptide, sevadicin, was recently characterized from laboratory cultures of P. larvae. In this study, paenilarvins, which are iturinic lipopeptides exhibiting strong antifungal activities, were obtained by bioassay-guided fractionation from cultures of P. larvae, genotype ERIC II. Their molecular structures were determined by extensive 2D NMR spectroscopy, high resolution mass spectrometry, and other methods. Paenilarvins are the first antifungal secondary metabolites to be identified from P. larvae. In preliminary experiments, these lipopeptides also affected honey bee larvae and might thus play a role in P. larvae survival and pathogenesis. However, further studies are needed to investigate their function.ChemBioChem 07/2014; 15:1947–1955. · 3.06 Impact Factor