Growth and adaptation of microorganisms on the cheese surface

Abstract

Microbial communities living on cheese surfaces are composed of various bacteria, yeasts and molds that interact together, thus generating the typical sensory properties of a cheese. Physiological and genomic investigations have revealed important functions involved in the ability of microorganisms to establish themselves at the cheese surface. These functions include the ability to use the cheese's main energy sources, to acquire iron, to tolerate low pH at the beginning of ripening and to adapt to high salt concentrations and moisture levels. Horizontal gene transfer events involved in the adaptation to the cheese habitat have been described, both for bacteria and fungi. In the future, in situ microbial gene expression profiling and identification of genes that contribute to strain fitness by massive sequencing of transposon libraries will help us to better understand how cheese surface communities function.

Biotic Interactions Shape the Ecological Distributions of Staphylococcus Species

“…S1 in the supplemental material). Salt and pH are two of the most important drivers of bacterial growth in cheese microbiomes, and both of these environmental variables change during the aging of cheese as S. equorum becomes more abundant (24, 35). In contrast to our prediction, S. xylosus had the broadest niche breadth as determined by total growth across the range of pH and salt concentrations, with S. equorum and S. saprophyticus having more restricted niches (Fig.…”

“…S3 in the supplemental material). Filamentous fungi produce large amounts of extracellular proteases, and these proteases may release free amino acids that could stimulate the growth of neighboring bacterial species (35, 46). Using a global metabolomics screen, we observed a substantial increase in the levels of many free amino acids when Scopulariopsis was grown on cheese curd agar, including a greater than 10-fold increase in levels of methionine (see Table S5).…”

“…Both fungal species caused a decrease in expression of genes associated with amino acid acquisition and metabolism, while only Scopulariopsis caused a decrease in expression of iron acquisition genes. Much of the iron in cheese is bound by lactoferrin, an iron chelator present in milk (35), and microbes that colonize cheese produce siderophores to cope with iron limitation (40). Free amino acids are also in low supply in fresh cheese, as they are bound up in casein (35).…”

“…Much of the iron in cheese is bound by lactoferrin, an iron chelator present in milk (35), and microbes that colonize cheese produce siderophores to cope with iron limitation (40). Free amino acids are also in low supply in fresh cheese, as they are bound up in casein (35). Scopulariopsis may alter the availability of both iron and free amino acids by a variety of mechanisms (Fig.…”

Extensive horizontal gene transfer in cheese-associated bacteria

“…Given that biofilms such as these are densely populated, and microbes in cheese rinds are under strong selection to obtain limited nutrients (e.g. free amino acids, iron) as well as tolerate cell stress (Monnet et al, 2015), we predicted that HGT might be widespread in cheese rind microbiomes and therefore might provide a useful experimental model for HGT within microbial communities.…”