Identification of Essential Genes Associated With Prodigiosin Production in Serratia marcescens FZSF02.

Xianbo Jia,Jichen Chen,Yu Fang,Shouping Cai,Hui Zhang,Junjie Lin,Longjun Chen,Chenqiang Lin,Ke Zhao,Fangchen Liu

doi:10.3389/fmicb.2021.705853

Abstract

Prodigiosin is a promising secondary metabolite produced mainly by Serratia strains. To study the global regulatory mechanism of prodigiosin biosynthesis, a mutagenesis library containing 23,000 mutant clones was constructed with the EZ-Tn5 transposon, and 114 clones in the library showed altered prodigiosin production ability. For 37 of the 114 clones, transposon insertion occurred on the prodigiosin biosynthetic cluster genes; transposon inserted genes of the 77 clones belonged to 33 different outside prodigiosin biosynthetic cluster genes. These 33 genes can be divided into transcription-regulating genes, membrane protein-encoding genes, and metabolism enzyme-encoding genes. Most of the genes were newly reported to be involved in prodigiosin production. Transcriptional levels of the pigA gene were significantly downregulated in 22 mutants with different inserted genes, which was in accordance with the phenotype of decreased prodigiosin production. Functional confirmation of the mutant genes involved in the pyrimidine nucleotide biosynthesis pathway was carried out by adding orotate and uridylate (UMP) into the medium. Gene complementation confirmed the regulatory function of the EnvZ/OmpR two-component regulatory system genes envZ and ompR in prodigiosin production.

Highlights

Prodigiosin is a pigment produced by strains of Serratia spp., Vibrio spp. (Borić et al, 2011), Streptomyces coelicolor (Liu et al, 2017), and other bacterial species
ATCC 39006 consisted of a gene pigO in its prodigiosin synthesis gene cluster, which was different with many Serratia spp. strains (Williamson et al, 2006)
The probability that the transposon inserted one certain gene was calculated with the formula P = 1 − (1 − X/G)n, where P is the property that one gene was found to be inserted by the transposon, X is the average length of the genes of the studied strain (1,800 bp for the S. marcescens FZSF02 strain used in this study), G is the genome length of the studied strain (5.6 × 106 bp for the S. marcescens FZSF02 strain), and n is the number of mutant clones obtained in the mutation library (Krysan et al, 1999; Song et al, 2015a)

Summary

Introduction

Prodigiosin is a pigment produced by strains of Serratia spp., Vibrio spp. (Borić et al, 2011), Streptomyces coelicolor (Liu et al, 2017), and other bacterial species. Some of the synthesis genes are involved in 2-methyl-3-n-amyl-pyrrole (MAP) synthesis, some are involved in the production of 4-methoxy-2,2'-bipyrrole-5carbaldehyde (MBC), and some are involved in the terminal step of prodigiosin synthesis with MAP and MBC (Williamson et al, 2006). ATCC 39006 consisted of a gene pigO in its prodigiosin synthesis gene cluster, which was different with many Serratia spp. strains (Williamson et al, 2006)

Methods

Results

Conclusion