Kunkecin A, a New Nisin Variant Bacteriocin Produced by the Fructophilic Lactic Acid Bacterium, Apilactobacillus kunkeei FF30-6 Isolated From Honey Bees

: Takeshi Zendo, Chihiro Ohashi, Shintaro Maeno, Xingguo Piao, Seppo Salminen, Kenji Sonomoto, Akihito Endo

Publisher: FRONTIERS MEDIA SA

: 2020

: Frontiers in Microbiology

: FRONTIERS IN MICROBIOLOGY

: FRONT MICROBIOL

: ARTN 571903

: 11

: 9

: 1664-302X

DOI: https://doi.org/10.3389/fmicb.2020.571903

: https://research.utu.fi/converis/portal/detail/Publication/50854215

Apilactobacillus kunkeeiFF30-6 isolated from healthy honey bees synthesizes the bacteriocin, which exhibits antimicrobial activity againstMelissococcus plutonius. The bacteriocin, kunkecin A, was purified through three-step chromatography, and mass spectrometry revealed that its relative molecular mass was 4218.3. Edman degradation of purified kunkecin A showed only the N-terminal residue, isoleucine. Hence, alkaline alkylation made the subsequent amino acid residues accessible to Edman degradation, and 30 cycles were sequenced with 11 unidentified residues. Whole genome sequencing ofA. kunkeeiFF30-6, followed by Sanger sequencing, revealed that the genes encoding the proteins involved in lantibiotic biosynthesis were within the plasmid, pKUNFF30-6. Most of the identified proteins exhibited significant sequence similarities to the biosynthetic proteins of nisin A and its variants, such as subtilin. However, the kunkecin A gene cluster lacked the genes corresponding tonisI,nisR, andnisKof the nisin A biosynthetic gene cluster. A comparison of the gene products ofkukAandnisA(kunkecin A and nisin A structural genes, respectively) suggested that they had similar post-translational modifications. Furthermore, the structure of kunkecin A was proposed based on a comparison of the observed and calculated relative molecular masses of kunkecin A. The structural analysis revealed that kunkecin A and nisin A had a similar mono-sulfide linkage pattern. Purified kunkecin A exhibited a narrow antibacterial spectrum, but high antibacterial activity againstM. plutonius. Kunkecin A is the first bacteriocin to be characterized in fructophilic lactic acid bacteria and is the first nisin-type lantibiotic found in the familyLactobacillaceae.

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