Genomic insights into the virulence and salt tolerance of Staphylococcus equorum

Do-Won Jeong,Sojeong Heo,Jochen Blom,Sangryeol Ryu,Jong-Hoon Lee

doi:10.1038/s41598-017-05918-5

Abstract

To shed light on the genetic background behind the virulence and salt tolerance of Staphylococcus equorum, we performed comparative genome analysis of six S. equorum strains. Data on four previously published genome sequences were obtained from the NCBI database, while those on strain KM1031 displaying resistance to multiple antibiotics and strain C2014 causing haemolysis were determined in this study. Examination of the pan-genome of five of the six S. equorum strains showed that the conserved core genome retained the genes for general physiological processes and survival of the species. In this comparative genomic analysis, the factors that distinguish the strains from each other, including acquired genomic factors in mobile elements, were identified. Additionally, the high salt tolerance of strains enabling growth at a NaCl concentration of 25% (w/v) was attributed to the genes encoding potassium voltage-gated channels. Among the six strains, KS1039 does not possess any of the functional virulence determinants expressed in the other strains.

Highlights

Staphylococcus equorum, initially isolated from a healthy horse[1], is a common component of the microbiota in the fermented foods of Europe, including fermented meat products[2,3,4] and smear-ripened and semi-hard cheeses[5, 6]
When the genome of strain KS1039 was established as the standard, a large-scale chromosomal reorganization by a single recombination event was found to have occurred in the genome of strain G8HB1, which resulted in the inversion of a genomic region; in addition, the results indicated that the genomes of strains Mu2 and UMC-Coagulase-negative staphylococci (CNS)-924 might have been generated by complex rearrangements
The previously reported analyses of the three genomes of S. equorum strains Mu2, UMC-CNS-924 and KS1039 revealed that these three strains do not possess any clear virulence factors found in the well-known pathogen S. aureus[10, 16, 17]

Summary

Introduction

Staphylococcus equorum, initially isolated from a healthy horse[1], is a common component of the microbiota in the fermented foods of Europe, including fermented meat products[2,3,4] and smear-ripened and semi-hard cheeses[5, 6] This species has been reported to produce low-molecular-weight aromatic compounds, such as esters, amino acids, aldehydes and free fatty acids, in food fermentation[7, 8]. The emergence of strains suspected of being involved in bovine mastitis[10], showing high prevalence of acquired phenotypes including antibiotic resistance and haemolysis[11,12,13], has necessitated safety assessments of this species In this context, safety assessments of starter candidates for traditional Spanish dry-cured sausages, dairy products, jeotgal and fermented meat products have been performed[12,13,14,15]. This study introduced intraspecific comprehensive comparative genome analysis to shed light on the genetic background behind the phenotypic characteristics

Methods

Results

Conclusion