Discovery of a novel lantibiotic nisin O from Blautia obeum A2-162, isolated from the human gastrointestinal tract

Abstract

A novel lanC-like sequence was identified from the dominant human gut bacterium Blautia obeum strain A2-162. This sequence was extended to reveal a putative lantibiotic operon with biosynthetic and transport genes, two sets of regulatory genes, immunity genes, three identical copies of a nisin-like lanA gene with an unusual leader peptide, and a fourth putative lanA gene. Comparison with other nisin clusters showed that the closest relationship was to nisin U. B. obeum A2-162 demonstrated antimicrobial activity against Clostridium perfringens when grown on solid medium in the presence of trypsin. Fusions of predicted nsoA structural sequences with the nisin A leader were expressed in Lactococcus lactis containing the nisin A operon without nisA. Expression of the nisA leader sequence fused to the predicted structural nsoA1 produced a growth defect in L. lactis that was dependent upon the presence of biosynthetic genes, but failed to produce antimicrobial activity. Insertion of the nso cluster into L. lactis MG1614 gave an increased immunity to nisin A, but this was not replicated by the expression of nsoI. Nisin A induction of L. lactis containing the nso cluster and nisRK genes allowed detection of the NsoA1 pre-peptide by Western hybridization. When this heterologous producer was grown with nisin induction on solid medium, antimicrobial activity was demonstrated in the presence of trypsin against C. perfringens, Clostridium difficile and L. lactis. This research adds to evidence that lantibiotic production may be an important trait of gut bacteria and could lead to the development of novel treatments for intestinal diseases.

First evidence of production of the lantibiotic nisin P

“…The prototypical nisin A gene cluster consists of the structural gene nisA , followed by nisBTCIPRKFEG 18 . The nisin P gene cluster in S. agalactiae DPC7040 has a similar gene order but the nipPRKFEG genes are located to the front of the nipA structural gene, a phenomenon which also occurs in the nisin U gene cluster 19 (Figure 3). The same gene order was observed when the nisin P gene cluster was first reported in the genome of Streptococcus suis 20 .…”

“…Nisin H, produced by Streptococcus hyointestinalis was the first variant isolated from a mammalian gastrointestinal (GI) tract (porcine) 15 and has five different amino acids at positions 1, 6, 18, 21 and 31. In 2017, a nisin O operon has been reported in Blautia obeum A2-162 isolated from a human GI tract 16 . Unusually this operon encodes 4 peptides, the first 3 being identical and exhibiting similarity to nisin U, and the fourth showing the highest divergence from nisin A.…”

First evidence of production of the lantibiotic nisin P

“…The prototypical nisin A gene cluster consists of the structural gene nisA, followed by nisBTCIPRKFEG 18 . The nisin P gene cluster in S. agalactiae DPC7040 has a similar gene order but the nipPRKFEG genes are located to the front of the nipA structural gene, a phenomenon which also occurs in the nisin U gene cluster 16 (Fig. 3).…”

“…lactis 1 Z L. lactis strain NIZO 22186 (dairy product) 9 Q L. lactis 61-14 (Japanese river water) 12 F L. lactis F10 (freshwater catfish) 11 U and U2 S. uberis strain 42 (bovine mammary secretions) 13 P Streptococcus gallolyticus subsp. pasteurianus 17 H S. hyointestinalis DPC 6484 (porcine intestine) 15 O Blautia obeum A2-162 (human GI tract) 16 Table 1. Summary of nisin variants reported in the literature.…”

“…5E). Additional peaks have an addition of 4 m/z corresponding to 16 Da, suggesting oxidation. Addition of 18 Da (H 2 O) (or multiples) cannot be seen, meaning that the major part of nisin P is completely dehydrated.…”