Staphylococcus aureus

Bacteria

Biology

Antimicrobial

Biochemistry

Strain (injury)

Genetics

Minimum inhibitory concentration

Membrane

Bacillus subtilis

Anatomy

Phosphatidylglycerol

Listeria monocytogenes

Microbiology

Phospholipid

Chemistry

Phosphatidylcholine

Bacillus (shape)

Bacillus pumilus

Marine Drugs

Producing antimicrobials is a common adaptive behavior shared by many microorganisms, including marine bacteria. We report that SF214, a marine-isolated strain of Bacillus pumilus, produces at least two different molecules with antibacterial activity: a molecule smaller than 3 kDa active against Staphylococcus aureus and a molecule larger than 10 kDa active against Listeria monocytogenes. We focused our attention on the anti-Staphylococcus molecule and found that it was active at a wide range of pH conditions and that its secretion was dependent on the growth phase, medium, and temperature. A mass spectrometry analysis of the size-fractionated supernatant of SF214 identified the small anti-Staphylococcus molecule as a pumilacidin, a nonribosomally synthesized biosurfactant composed of a mixture of cyclic heptapeptides linked to fatty acids of variable length. The analysis of the SF214 genome revealed the presence of a gene cluster similar to the srfA-sfp locus encoding the multimodular, nonribosomal peptide synthases found in other surfactant-producing bacilli. However, the srfA-sfp cluster of SF214 differed from that present in other surfactant-producing strains of B. pumilus by the presence of an insertion element previously found only in strains of B. safensis.

A Marine Isolate of Bacillus pumilus Secretes a Pumilacidin Active against Staphylococcus aureus