Pentocin KCA1: a novel circular bacteriocin gene encoded in the genome of Lactobacillus pentosus KCA1 with putative basic property

Abstract

Background: The use of bacteriocin and bacterial strains that produces the antimicrobial peptide has shown to possess potential applications in the conferment of health benefits on the host. We isolated and carried out comprehensive genome sequence analysis of the first Lactobacillus pentosus KCA1 of human origin encoding genes for the biosynthesis of antimicrobial bacteriocin peptide. Due to the growing number of antimicrobial resistance, the need for developing alternatives to traditional antibiotics is now more germane.

Aims: To describe the first circular bacteriocin predicted in the genome sequence of Lactobacillus pentosus KCA1 isolated from the vagina of a healthy Nigerian Ibo woman using in silico bioinformatic tools.

Methods: The translated open reading frame (ORF) coding pentocin KCA1 was compared with the non-redundant database (nrdb) using BLASTp for protein similarity search. Clustalw algorithm was used for alignment with other published circular bacteriocins.

Results: The genome of L. pentosus KCA1 contains a 7-gene cluster, chromosomally encoded for biosynthesis of a predicted circular bacteriocin. The bacteriocin designated as “pentocin KCA1” is synthesized as a precursor gene consisting of 273 nucleotide base sequence encoding the translated product of pentocin KCA1 with 91 amino acid residues in length. The peptide is cleaved off between asparagine (Asn33) and isoleucine (Ile34) to produce the 58 amino acid pentocin KCA1 as an outer membrane peptide. The mature pentocin KCA1 has a high proportion of basic (positively charged-Lysine, Histidine and Asparagine) to acidic (negatively charged-Glutamate and Aspartate) amino acids in the ratio of 8:0.

Conclusions: Off the 11 circular bacteriocins known to date, amino acid residue asparagine (8.62%) is utilized more in the biosynthesis of pentocin KCA1. The mature putative circular pentocin KCA1 consists of four alpha-helical structures and has a high proportion of basic amino acid residues when compared with other circular bacteriocins, thereby suggesting that pentocin KCA1 is a circular bacteriocin peptide with strong basic property. The relevance of this basic property lends credence for investigation in subsequent functional studies.

Keywords: Circular bacteriocin, Pentocin KCA1, Lactobacilli, Antimicrobial peptide