Bacillus cereus Group-Type Strain-Specific Diagnostic Peptides

Abstract

The Bacillus cereus group consists of eight very closely related species and comprises both harmless and human pathogenic species such as Bacillus anthracis, Bacillus cereus, and Bacillus cytotoxicus. Numerous efforts have been undertaken to allow presumptive differentiation of B. cereus group species from one another. However, methods to rapidly and accurately distinguish these species are currently lacking. We confirmed that classical matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) biotyping cannot achieve reliable identification of each type strain. We therefore assigned type strain-specific diagnostic peptides to the B. cereus group based on comparisons of their proteomic profiles. The number of diagnostic peptides varied remarkably in a type strain-dependent manner. The accuracy of the reference database was crucial to validate candidate diagnostic peptides and led to a noteworthy reduction of verified diagnostic peptides. Diagnostic peptides ranged from one for B. weihenstephanensis to 62 for B. pseudomycoides and were associated with proteins involved in diverse biological processes, e.g. amino acid biosynthesis, cell envelope, cellular processes, energy metabolism, and transport processes. However, 45.6% of all diagnostic peptides comprised currently unclassified proteins or proteins of unknown function. In addition, a phylogenetic tree based on clustering of theoretical precursor masses deduced from in silico-generated tryptic peptides was reconstructed.

Dynamics of culturable mesophilic bacterial communities of three fresh herbs and their production environment

“…However, a separation between members of the group was not possible even though certain isolates clearly differed in colony morphology as reported recently (Pfrunder et al . ). Such difficulties are well‐known for the B. cereus group since their 16S rRNA sequences display less than 1% difference (Ash et al .…”

“…After incubation, either direct smearing or protein extraction from the freshly grown colonies was performed (Gekenidis et al 2014), whenever the direct smearing did not yield satisfactory results. It is noteworthy, that classical MALDI biotyping is limited in discriminating species belonging to the B. cereus group (Pfrunder et al 2016) and therefore the composition of the B. cereus group could not be resolved. For MALDI-TOF mass spectrometric measurements, 1 ll of each protein extract was spotted onto a MALDI target, left to dry and covered with 1Á2 ll of matrix solution (10 mg ml À1 a-cyano-4hydroxycinnamic acid (Bruker Daltonics, Bremen, Germany) in acetonitrile-water-trifluoroacetic acid (50 : 47Á5 : 2Á5 (vol/vol/vol), Sigma-Aldrich).…”

Non-Toxin-Producing Bacillus cereus Strains Belonging to the B. anthracis Clade Isolated from the International Space Station

“…All of the ISS isolates were identified as members of the B. cereus group and shared their fingerprint with B. anthracis Ames (data not shown). More recently, proteome-based analysis of B. cereus group strains revealed a cluster comprising B. cereus , B. anthracis , B. thuringiensis , B. mycoides , B. weihenstephanensis , and B. toyonensis , which have more accurate m/z values in common than the remaining species B. cytotoxicus and B. pseudomycoides (33). Thus, MALDI profiles were not useful for delineation of the members of the B. cereus group, as reported here and elsewhere (33).…”

Are injectable illegal polypeptide drugs safe? Case report demonstrating the presence of haemolytic Bacillus cereus in 2 illegal peptide drugs

“…This group however, contains 8 species ( B. anthracis, B. cereus , B. cytotoxicus, B. mycoides, B. pseudomycoides, B. thuringiensis, B. toyonensis and B. weihenstephanensis ) which have a very high genetic (both in genetic synteny and content) and spectral resemblance. Therefore, the MALDI–TOF Biotyper methodology does not enable us to distinguish between the spectra of Bacillus cereus and the other closely related members such as Bacillus anthracis and Bacillus thurigiensis . Therefore, again at least 20 colonies were picked and pooled for analysis with PCR to verify if these samples indeed contained this microorganism.…”