An antimicrobial peptide specifically active against Listeria monocytogenes is secreted by Bacillus pumilus SF214

Abstract

Background Members of the Bacillus genus produce a large variety of antimicrobial peptides including linear or cyclic lipopeptides and thiopeptides, that often have a broad spectrum of action against Gram-positive and Gram-negative bacteria. We have recently reported that SF214, a marine isolated strain of Bacillus pumilus, produces two different antimicrobials specifically active against either Staphylococcus aureus or Listeria monocytogenes. The anti-Staphylococcus molecule has been previously characterized as a pumilacidin, a nonribosomally synthesized lipopetide composed of a mixture of cyclic heptapeptides linked to fatty acids of variable length. Results Our analysis on the anti-Listeria molecule of B. pumilus SF214 indicated that it is a peptide slightly smaller than 10 kDa, produced during the exponential phase of growth, stable at a wide range of pH conditions and resistant to various chemical treatments. The peptide showed a lytic activity against growing but not resting cells of Listeria monocytogenes and appeared extremely specific being inactive also against L. innocua, a close relative of L. monocytogenes. Conclusions These findings indicate that the B. pumilus peptide is unusual with respect to other antimicrobials both for its time of synthesis and secretion and for its strict specificity against L. monocytogenes. Such specificity, together with its stability, propose this new antimicrobial as a tool for potential biotechnological applications in the fight against the dangerous food-borne pathogen L. monocytogenes.

Modulation of intestinal epithelial cell proliferation and apoptosis by Lactobacillus gasseri SF1183

“…Cell viability was assessed using the MTT assay (Sigma-Aldrich). It is based on the reduction of the tetrazolium ring of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) by mitochondrial dehydrogenases, yielding a purple dye (formazan), which can be measured spectrophotometrically; the amount of formazan produced is proportional to the number of viable cells 31 . HCT116 cells were seeded in 96-well plates (9 × 10 3 cells/well).…”

Comparative Genomics and Physiological Characterization of Two Aerobic Spore Formers Isolated from Human Ileal Samples

“…Cytotoxicity on HCT 116 cells was assessed by performing the MTT reduction inhibition assay. Cells were grown as described and plated on 96-well plates at a density of 5 × 10 3 cells per well, in 200 µL of medium containing SF106/SF174 cell-free supernatants (20% v/v ) for 24 h [ 19 ]. After treatment, the medium was eliminated and 10 µL of a stock MTT reagent was added into each well to a final concentration of 0.5 mg/mL.…”

“…Germination-derived cells of several Bacillus species also interact with immune cells contributing to the GALT maturation and to the development of the pre-immune antibody repertoire [ 10 ], upregulating the expression of the Toll-like receptors TLR2 and TLR4 [ 14 ] and by secreting useful metabolites. Examples of such metabolites are peptides and lipopeptides with antimicrobial activity [ 18 , 19 ] and quorum-sensing peptides, such as the Competence and Sporulation Factor (CSF) of B. subtilis [ 20 ]. CSFs of B. subtilis and CSF-like peptides produced by other Bacillus species induce the synthesis of the heat-shock (HS) proteins in human cells in vitro [ 20 , 21 ] and prevent oxidant-induced intestinal epithelial injuries and loss of barrier function, exerting cytoprotective activities in vivo [ 20 ].…”

Sporulation efficiency and spore quality in a human intestinal isolate of Bacillus cereus

“…For SEM analysis, MV19 spores (1.0×10 8 /mL) prepared at different temperatures were cut from subapical parts using a sharp razor blade, fixed with 3% glutaraldehyde in phosphate buffer (65 mM, pH 7.2–7.4) for 2 h at room temperature, post-fixed with 1% osmium tetroxide in the same phosphate buffer for 1.5 h at room temperature, and completely dehydrated with ethanol. Both samples were then mounted on aluminium stubs, coated with a thin gold film using an EdwardE306 Evaporator, and observed with a FEI (Hills-boro, OR, USA) Quanta 200 ESEM in high vacuum mode (P 70 Pa, HV 30 kV, WD10 mm, spot 3.0) (Saggese et al 2022).…”