The Lactococcus lactis KF147 nonribosomal peptide synthetase/polyketide synthase system confers resistance to oxidative stress during growth on plant leaf tissue lysate.

Benjamin L Golomb,Laurynne C Coates,Annabelle O Yu,Maria L Marco

doi:10.1002/mbo3.531

Benjamin L Golomb, Laurynne C Coates + Show 2 more

Open Access

https://doi.org/10.1002/mbo3.531

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Journal: MicrobiologyOpen	Publication Date: Sep 18, 2017
Citations: 13	License type: CC BY 4.0

Affiliation: University of California, Davis

Abstract

Strains of Lactococcus lactis isolated from plant tissues possess adaptations that support their survival and growth in plant‐associated microbial habitats. We previously demonstrated that genes coding for a hybrid nonribosomal peptide synthetase/polyketide synthase (NRPS/PKS) system involved in production of an uncharacterized secondary metabolite are specifically induced in L. lactis KF147 during growth on plant tissues. Notably, this NRPS/PKS has only been identified in plant‐isolated strains of L. lactis. Here, we show that the L. lactis KF147 NRPS/PKS genes have homologs in certain Streptococcus mutans isolates and the genetic organization of the NRPS/PKS locus is conserved among L. lactis strains. Using an L. lactis KF147 mutant deficient in synthesis of NrpC, a 4′‐phosphopantetheinyl transferase, we found that the NRPS/PKS system improves L. lactis during growth under oxidative conditions in Arapidopsis thaliana leaf lysate. The NRPS/PKS system also improves tolerance of L. lactis to reactive oxygen species and specifically H2O2 and superoxide radicals in culture medium. These findings indicate that this secondary metabolite provides a novel mechanism for reactive oxygen species detoxification not previously known for this species.

Highlights

Numerous bacterial species in multiple phyla possess the capacity to synthesize secondary metabolite peptides and carboxy acids by nonribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) (Weissman, 2015)
The L. lactis KF147 genes coding for the NRPS/PKS system span over 40 kb and consist of a two-component response regulator, biosynthetic enzymes, a 4′-phosphopantetheinyl transferase (PPTase, nrpC), and a putative ATP-binding cassette (ABC) transporter (Figure 1)
Numerous lactic acid bacteria (LAB) species are annotated to contain NRPS/ PKS systems, few have been biochemically characterized and these are limited to Lactobacillus reuteri TMW1.656 (Lin et al, 2015) and S. mutans UA159 (Joyner et al, 2010), and UA140 (Wu et al, 2010)

Summary

| INTRODUCTION

Numerous bacterial species in multiple phyla possess the capacity to synthesize secondary metabolite peptides and carboxy acids by nonribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) (Weissman, 2015). Strains of Lactococcus lactis are among the most extensively characterized LAB and are used in a variety of applications including starter cultures in cheese production (Cavanagh, Fitzgerald, & McAuliffe, 2015), industrial product synthesis (Mierau et al, 2005), and for the delivery of therapeutics to the human gastrointestinal. We examine the genetic relatedness of the NRPS/PKS to other lactococci and Streptococcus mutans strains and demonstrate the contribution of the secondary metabolite to L. lactis growth in oxidative conditions, most appreciably on plant tissues

| EXPERIMENTAL PROCEDURES

| RESULTS AND DISCUSSION

| CONCLUSIONS