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Poppinga, L, Janesch, B, Fünfhaus, A, Sekot, G, Garcia-Gonzalez, E, Hertlein, G, Hedtke, K, Schäffer, C and Genersch, E (2012) Identification and functional analysis of the S-layer protein SplA of Paenibacillus larvae, the causative agent of American Foulbrood of honey bees. PLoS Pathog. 8:e1002716


The gram-positive, spore-forming bacterium Paenibacillus larvae is the etiological agent of American Foulbrood (AFB), a globally occurring, deathly epizootic of honey bee brood. AFB outbreaks are predominantly caused by two genotypes of P. larvae, ERIC I and ERIC II, with P. larvae ERIC II being the more virulent genotype on larval level. Recently, comparative proteome analyses have revealed that P. larvae ERIC II but not ERIC I might harbour a functional S-layer protein, named SplA. We here determine the genomic sequence of splA in both genotypes and demonstrate by in vitro self-assembly studies of recombinant and purified SplA protein in combination with electron-microscopy that SplA is a true S-layer protein self-assembling into a square 2D lattice. The existence of a functional S-layer protein is novel for this bacterial species. For elucidating the biological function of P. larvae SplA, a genetic system for disruption of gene expression in this important honey bee pathogen was developed. Subsequent analyses of in vivo biological functions of SplA were based on comparing a wild-type strain of P. larvae ERIC II with the newly constructed splA-knockout mutant of this strain. Differences in cell and colony morphology suggest that SplA is a shape-determining factor. Marked differences between P. larvae ERIC II wild-type and mutant cells with regard to (i) adhesion to primary pupal midgut cells and (ii) larval mortality as measured in exposure bioassays corroborate the assumption that the S-layer of P. larvae ERIC II is an important virulence factor. Since SplA is the first functionally proven virulence factor for this species, our data extend the knowledge of the molecular differences between these two genotypes of P. larvae and contribute to explaining the observed differences in virulence. These results present an immense advancement in our understanding of P. larvae pathogenesis.


PubMed PMC3355101 Online version:10.1371/journal.ppat.1002716


Amino Acid Sequence; Animals; Bacterial Adhesion; Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Bees/microbiology; Cells, Cultured; Gene Knockout Techniques; Genotype; Larva/microbiology; Membrane Glycoproteins/chemistry; Membrane Glycoproteins/genetics; Membrane Glycoproteins/metabolism; Paenibacillus/pathogenicity; Sequence Alignment; Virulence Factors/chemistry; Virulence Factors/genetics; Virulence Factors/metabolism



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status



GO:0044406: adhesion of symbiont to host

ECO:0000315: mutant phenotype evidence used in manual assertion


Seeded From UniProt



GO:0044406: adhesion to host



Figure 5 shows that in an adhesion assay the splA knockout mutant had as little as 5.36% of the adhesion capacity to larval midgut cells compared to that of the ERICII (04-309wt) wild-type allele.

CACAO 7652

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