Abstract
Serratia marcescens RSC-14 is a Gram-negative bacterium that was previously isolated from the surface-sterilized roots of the Cd-hyperaccumulator Solanum nigrum. The strain stimulates plant growth and alleviates Cd stress in host plants. To investigate the genetic basis for these traits, the complete genome of RSC-14 was obtained by single-molecule real-time sequencing. The genome of S. marcescens RSC-14 comprised a 5.12-Mbp-long circular chromosome containing 4,593 predicted protein-coding genes, 22 rRNA genes, 88 tRNA genes, and 41 pseudogenes. It contained genes with potential functions in plant growth promotion, including genes involved in indole-3-acetic acid (IAA) biosynthesis, acetoin synthesis, and phosphate solubilization. Moreover, annotation using NCBI and Rapid Annotation using Subsystem Technology identified several genes that encode antioxidant enzymes as well as genes involved in antioxidant production, supporting the observed resistance towards heavy metals, such as Cd. The presence of IAA pathway-related genes and oxidative stress-responsive enzyme genes may explain the plant growth-promoting potential and Cd tolerance, respectively. This is the first report of a complete genome sequence of Cd-tolerant S. marcescens and its plant growth promotion pathway. The whole-genome analysis of this strain clarified the genetic basis underlying its phenotypic and biochemical characteristics, underpinning the beneficial interactions between RSC-14 and plants.
Highlights
Plants harbor a diverse community of endophytic bacteria that live in close association, without triggering the disruption or apparent impairment of hosts [1]
We report the complete genome sequence of the Cd-tolerant plant growth-promoting (PGP) strain S. marcescens RSC-14 to elucidate the genetic traits involved in metal tolerance and plant growth promotion and to define the primary characteristics responsible for endophytism
Our results revealed that the genome of S. marcescens RSC-14 carries many genes that may be useful for integrated bioremediation and that may improve the growth of hyperaccumulator plants, such as S. nigrum
Summary
Plants harbor a diverse community of endophytic bacteria that live in close association, without triggering the disruption or apparent impairment of hosts [1]. In such symbiotic associations, both partners, i.e., the microorganism and host plant, benefit by the mutual interaction with respect to overall fitness. Endophytic bacteria improve host plant growth via phytohormone and siderophore production, nitrogen fixation, and phosphate solubilization or by induced systematic resistance, competition for nutrients, and protection against abiotic stress. Complete genome of Serratia marcescens RSC-14 and pathogens [2]. These mechanisms are of prime importance for plants that are used for large-scale biomass production, especially in phytoremediation. Bacterial endophytes exhibit broad diversity; representative genera include Bacillus, Pseudomonas, Azospirillum, Burkholderia, and Serratia, and colonize different plant organs [3, 4, 5]
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