Identification and Characterization of pantocin wh-1, a Novel Cyclic Polypeptide Produced by Pantoea dispersa W18

Abstract

Pantoea dispersa W18, isolated from contaminated soil, was found to exert antimicrobial activity against Mycobacterium species, including Mycobacterium tuberculosis, an important human pathogen. Here, the anti-mycobacterial compound produced by Pantoea dispersa W18 was purified by a combination of hydrophobic interaction chromatography, cation exchange chromatography, and reverse phase HPLC. Active compounds from Pantoea dispersa W18 were identified as a natural peptide named pantocin wh-1 with a 1927 Da molecular weight. The primary structure of this compound was detected by N-terminal amino acid sequencing. The amino acid sequence of pantocin wh-1 consisted of 16 amino acid residues with a cyclic structure. The pantocin wh-1 could be inactivated by protease K, but was heat stable and unaffected by pH (2-12). However, the activity was not completely inactivated by trypsin and pepsin. This is the first report of a cyclic polypeptide purified from a strain of Pantoea dispersa.

Keywords: Mycobacterium tuberculosis; Pantoea dispersa; peptide natural products.

Figure 1

(A) On a plate of M. smegmatis, a yellow colony is shown to secrete active substances to inhibit the growth of M. smegmatis mc² 155; (B) using the oxford cup method, the cell-free supernatant (CFS) of the fermentation broth of this unknown strain exhibits antibacterial activity against M. smegmatis mc² 155.

Figure 2

Time course of pantocin wh-1 production during the growth of P. dispersa W18 in: (A) simple 7H9 medium; (B) Spizizen’s medium; (C) LB medium; and (D) MH medium. The amount of pantocin wh-1 is expressed as arbitrary units per milliliter (AU/mL). The indicator strain was M. smegmatis mc² 155.

Figure 3

Bactericidal activity of pantocin wh-1 against M. smegmatis mc² 155.

Figure 4

Antimicrobial activity of pantocin wh-1 in a mouse model.