Genomic Features and Construction of Streamlined Genome Chassis of Nisin Z Producer Lactococcus lactis N8.

Wanjin Qiao,Haijin Xu,Yu Qiao,Mingqiang Qiao,Per Erik Joakim Saris,Zhenzhou Wu,Fulu Liu,Ran Li,Xing Wan

doi:10.3390/microorganisms10010047

Wanjin Qiao, Haijin Xu + Show 7 more

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https://doi.org/10.3390/microorganisms10010047

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Abstract

Lactococcus lactis is a commonly used fermenting bacteria in cheese, beverages and meat products. Due to the lack of simplified chassis strains, it has not been widely used in the fields of synthetic biology. Thus, the construction of lactic acid bacteria chassis strains becomes more and more important. In this study, we performed whole genome sequencing, annotation and analysis of L. lactis N8. Based on the genome analysis, we found that L. lactis N8 contains two large plasmids, and the function prediction of the plasmids shows that some regions are related to carbohydrate transport/metabolism, multi-stress resistance and amino acid uptake. L. lactis N8 contains a total of seven prophage-related fragments and twelve genomic islands. A gene cluster encoding a hybrid NRPS–PKS system that was found in L. lactis N8 reveals that the strain has the potential to synthesize novel secondary metabolites. Furthermore, we have constructed a simplified genome chassis of L. lactis N8 and achieved the largest amount of deletion of L. lactis so far. Taken together, the present study offers further insights into the function and potential role of L. lactis N8 as a model strain of lactic acid bacteria and lays the foundation for its application in the field of synthetic biology.

Highlights

Lactococcus lactis, a group of Gram-positive, catalase-negative, mesophilic fermentative bacteria producing lactic acid from sugar [1], has a long history of safe use in the fermented food industry and is granted a “GRAS” status
The coding regions of N8 have a guanine plus cytosine (GC) content of 35.1 mol%, which is comparable to the other L. lactis strains
To visualize the position of L. lactis N8 within the species, we constructed an unrooted phylogenetic tree using all L. lactis currently published on NCBI

Summary

Introduction

Lactococcus lactis, a group of Gram-positive, catalase-negative, mesophilic fermentative bacteria producing lactic acid from sugar [1], has a long history of safe use in the fermented food industry and is granted a “GRAS” (generally regarded as safe) status. Lactis biovar diacetylactis, which distinguishes itself based on the citrate metabolism. A typical L. lactis chromosome ranges in size from ~2.2 to 2.6 Mb and is often accompanied by plasmid complements [3] and multiple remnant prophages [4]. L. lactis N8 (N8) is a nisin Z producer isolated from milk in Finland, and the knowledge gained from fundamental research on this nisin production strain has been exploited for a wide variety of biotechnological applications. Due to the feature of considerable nisin yield, the research on this strain so far has mainly

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