Growth of Aerobic Ripening Bacteria at the Cheese Surface Is Limited by the Availability of Iron

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>The microflora on the surface of smear-ripened cheeses is composed of various species of bacteria and yeasts that contribute to the production of the desired organoleptic properties. The objective of the present study was to show that iron availability is a limiting factor in the growth of typical aerobic ripening bacteria in cheese. For that purpose, we investigated the effect of iron or siderophore addition in model cheeses that were coinoculated with a yeast and a ripening bacterium. Both iron and the siderophore desferrioxamine B stimulated the growth of ripening bacteria belonging to the genera<jats:named-content content-type="genus-species">Arthrobacter</jats:named-content>,<jats:named-content content-type="genus-species">Corynebacterium</jats:named-content>, and<jats:named-content content-type="genus-species">Brevibacterium</jats:named-content>. The extent of stimulation was strain dependent, and generally, the effect of desferrioxamine B was greater than that of iron. Measurements of the expression of genes related to the metabolism of iron by<jats:named-content content-type="genus-species">Arthrobacter arilaitensis</jats:named-content>Re117 by real-time reverse transcription-PCR showed that these genes were transcribed during growth in cheese. The addition of desferrioxamine B increased the expression of two genes encoding iron-siderophore ABC transport binding proteins. The addition of iron decreased the expression of siderophore biosynthesis genes and of part of the genes encoding iron-siderophore ABC transport components. It was concluded that iron availability is a limiting factor in the growth of typical cheese surface bacteria. The selection of strains with efficient iron acquisition systems may be useful for the development of defined-strain surface cultures. Furthermore, the importance of iron metabolism in the microbial ecology of cheeses should be investigated since it may result in positive or negative microbial interactions.</jats:p>

Extensive Horizontal Gene Transfer in Cheese-Associated Bacteria

“…Although previous studies demonstrated that iron is limiting for Glutamicibacter, Brevibacterium, and Corynebacterium species growing on cheese (Monnet et al, 2012(Monnet et al, , 2010, the preponderance of siderophore and other iron acquisition genes we observed being horizontally transferred suggests that the same is true across bacterial phyla. Limiting iron is a deliberate strategy on the part of mammalian hosts to block the growth of infectious microbes, and this strategy influences the composition of milk because of the presence of lactoferrin (Ellison, 1994).…”

“…Five of the 10 largest HGT groups as measured by total number of genes (Groups 1, 2, 3, 7 and 8) contained siderophore transport systems (K02013-K02016). Low availability of iron in cheese is known to limit the growth of several bacterial species (Monnet et al, 2012(Monnet et al, , 2010. Previous work has also shown that genes involved in iron acquisition are present in higher numbers in cheese-associated species compared with closely related species from other environments (Monnet et al, 2010;Walter et al, 2014).…”

“…Horizontally transferred genes are not always expressed in the recipient genome, because of possible incompatibilities in promoter sequence (Ochman et al, 2000). As iron is a limiting resource in cheese (Kastman et al, 2016;Monnet et al, 2012), we reasoned that if RUSTI is a functional operon, it would likely have increased expression in the presence of additional competition for iron. To assess whether RUSTI genes are regulated in the presence of competition, we grew G. arilaitensis JB182 alone or in the presence of Penicillium and performed RNA sequencing (RNA-seq) to monitor gene expression.…”

Application of PCR-Based Methods to Dairy Products and to Non-Dairy Probiotic Products

“…A similar approach was applied for the study of the growth of L. lactis subsp. cremoris strains under conditions simulating cheddar cheese manufacture (Taïbi et al, 2011) and for the study of iron acquisition by Arthrobacter arilaitensis in experimental cheeses (Monnet et al, 2012 Experimental cheeses L. lactis subsp. lactis bcaT, codY, serA, cysK, gltD, lacC, gapA, gapB, pdhB, aldB, butA, noxE, murF, dnaK, chiA, pepN, gyrB, pi139, pi302 Experimental cheeses (Cretenet et al, 2011) L. lactis subsp.…”

Quantification of Yeast and Bacterial Gene Transcripts in Retail Cheeses by Reverse Transcription-Quantitative PCR

“…For example, it is interesting to supplement genomic data, which give indications of the potential of a given microorganism in terms of metabolic activities, with gene expression data, which reveal the true capabilities of the microorganism inside the food product. Gene expression analyses have been performed with experimental cheeses or experimental fermented milks (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). To our knowledge, no study devoted to the quantification of gene transcripts in retail cheeses has been published as of this time.…”