GSE136873
Novel inducible filamentous sliding motility identified in pathogenic Bacillus cereus group species
We isolated an atmospheric contaminant, subsequently identified as a new strain of Bacillus mobilis, which showed a novel, robust, inducible filamentous sliding motility and completely colonized a bacterial culture plate in less than 48 h under some conditions. This flagella-independent sliding motility was characterized by long filamentous cells at the expanding edge, and was induced when cells were inoculated onto lawns of metabolically inactive Campylobacter jejuni cells, heat killed bacterial biomass, and milk or blood dried onto agar plates. Phosphatidylcholine (PC), bacterial membrane components, and sterile human fecal extracts were sufficient to induce filamentous expansion. Screening of eight other Bacillus spp. (five from the B. cereus group and three other Bacillus spp.) showed that filamentous motility was conserved amongst B. cereus group species to varying degrees. RNAseq of filamentously expanding cells collected from PC and milk lawn plates in comparison to rod-shaped cells from control plates revealed that genes related to metabolism, ion and amino acid transport were differently regulated, genes controlling sporulation were reduced, and some virulence genes (e.g., hblA/B/C/D and plcR) were increased. We hypothesize that the robust and conserved nature of filamentous motility in pathogenic B. cereus group species can enhance bacterial colonization during host colonization. Overall design: Growth of B. mobilis ML-A2C4 on three different agar plate conditions were tested at n=3 biological replicates each for a total of 9 samples. The growth conditions are 1) control: growth on control MH 1.5% agar plates, 2) milk: growth on MH 1.5% agar plates covered with an adsorbed milk layer prepared by drying 1.5 mL of 10% smilk milk powder solution onto the surface of the plate, and 3) PC: growth on MH 1.5% agar plates that were spread plated with 0.5mL of a 2% phosphatidylcholine (PC) in 50% EtOH.