EFFECT OF ESSENTIAL OILS ON THE VIABILITY AND MORPHOLOGY OF ESCHERICHIA-COLI (SP-11)

The four essential oils (aromatic plant products) from palmarosa (Pm), lemongrass (Lg), peppermint (Pt) and eucalyptus (Eu) plants were foun d to be bactericidal to Escherichia coli strain SP-11, at a concentrat ion of 1.66 (Pm, Lg and Eu) or 2.5 (Pt) mu l ml(-1). This effect was o bserved both at 37 degrees C and 4 degrees C and was not prevented by immediate tenfold dilution or by the presence of 0.5 M sucrose. Pm and Pt but not Lg or Eu induced the formation of elongated filamentous fo rms, some measuring 60-70 mu m long.