Transcriptomic Analysis of Staphylococcus xylosus in Solid Dairy Matrix Reveals an Aerobic Lifestyle Adapted to Rind.

Sabine Leroy,Anne De La Foye,Pierre Micheau,Valérie Laroute,Régine Talon,Sergine Even,Yves Le Loir

doi:10.3390/microorganisms8111807

Abstract

Staphylococcus xylosus is found in the microbiota of traditional cheeses, particularly in the rind of soft smeared cheeses. Despite its frequency, the molecular mechanisms allowing the growth and adaptation of S. xylosus in dairy products are still poorly understood. A transcriptomic approach was used to determine how the gene expression profile is modified during the fermentation step in a solid dairy matrix. S. xylosus developed an aerobic metabolism perfectly suited to the cheese rind. It overexpressed genes involved in the aerobic catabolism of two carbon sources in the dairy matrix, lactose and citrate. Interestingly, S. xylosus must cope with nutritional shortage such as amino acids, peptides, and nucleotides, consequently, an extensive up-regulation of genes involved in their biosynthesis was observed. As expected, the gene sigB was overexpressed in relation with general stress and entry into the stationary phase and several genes under its regulation, such as those involved in transport of anions, cations and in pigmentation were up-regulated. Up-regulation of genes encoding antioxidant enzymes and glycine betaine transport and synthesis systems showed that S. xylosus has to cope with oxidative and osmotic stresses. S. xylosus expressed an original system potentially involved in iron acquisition from lactoferrin.

Highlights

Cheeses are one of the oldest fermented products, representing more than 1400 varieties of traditional cheeses around the world and nearly 1000 varieties in France [1]
Staphylococcus aureus grown in the same solid dairy matrix did not acidify the medium [25]
This study provides an extensive view of S. xylosus transcriptome when grown in a solid dairy matrix

Summary

Introduction

Cheeses are one of the oldest fermented products, representing more than 1400 varieties of traditional cheeses around the world and nearly 1000 varieties in France [1] Their microbial communities, composed of “house microbiota” and starters, are shaped by the technological processes and contribute to the development of the sensorial properties of cheeses. Studies of this microbial diversity combining phenotypic and genomic approaches have revealed two ecosystems, the core and the rind. S. xylosus is commercially available as an adjunct culture to enhance the aroma and texture of cheeses, as well as the color of the surface of smeared cheeses [13]

Methods

Results

Conclusion