The structure of a peptidolipid isolated from a pectolytic strain of Pseudomonas fluorescens biovar I1 has been determined by using mass spectrometry, NMR spectroscopy, and chemical methods. The compound was identified as viscosin, an antiviral peptidolipid first isolated from P. uiscosa. The native peptidolipid is a potent surfactant that facilitates bacterial infection and the spread of decay on nonwounded broccoli florets colonized by these pathogenic bacteria.