Insights into Penicillium roqueforti Morphological and Genetic Diversity

Abstract

Fungi exhibit substantial morphological and genetic diversity, often associated with cryptic species differing in ecological niches. Penicillium roqueforti is used as a starter culture for blue-veined cheeses, being responsible for their flavor and color, but is also a common spoilage organism in various foods. Different types of blue-veined cheeses are manufactured and consumed worldwide, displaying specific organoleptic properties. These features may be due to the different manufacturing methods and/or to the specific P. roqueforti strains used. Substantial morphological diversity exists within P. roqueforti and, although not taxonomically valid, several technological names have been used for strains on different cheeses (e.g., P. gorgonzolae, P. stilton). A worldwide P. roqueforti collection from 120 individual blue-veined cheeses and 21 other substrates was analyzed here to determine (i) whether P. roqueforti is a complex of cryptic species, by applying the Genealogical Concordance Phylogenetic Species Recognition criterion (GC-PSR), (ii) whether the population structure assessed using microsatellite markers correspond to blue cheese types, and (iii) whether the genetic clusters display different morphologies. GC-PSR multi-locus sequence analyses showed no evidence of cryptic species. The population structure analysis using microsatellites revealed the existence of highly differentiated populations, corresponding to blue cheese types and with contrasted morphologies. This suggests that the population structure has been shaped by different cheese-making processes or that different populations were recruited for different cheese types. Cheese-making fungi thus constitute good models for studying fungal diversification under recent selection.

Fertility depression among cheese‐makingPenicillium roquefortistrains suggests degeneration during domestication

“…This lack of intrinsic barriers to gene flow reinforces the previous inference based on multiple gene genealogies (Gillot et al. ) that the P. roqueforti genetic clusters likely do not represent cryptic species, but instead differentiated populations from a single species. The lack of differences in the ultrastructure of asci and ascospores further supports this view.…”

“…; Gillot et al. ). Only 31 strains from other environments than cheese were however available while they represented the most genetically diverse cluster.…”

“…A previous studies have in fact shown that the two cheese clusters corresponded to different cheese protected designations of origin and showed different morphologies, colors, and growth rates (Gillot et al. ). The two clusters may therefore correspond to independent selection events, of different strains, with contrasted phenotypic and physiologic traits for making different types of cheeses.…”

“…Penicillium roqueforti does not exclusively occur in cheese, it can also be found as a spoilage agent in refrigerated stored foods or other habitats, such as silage, wood, and forest soil (Samson 2000;Pitt and Hocking 2009;Ropars et al 2012a). Previous population studies using microsatellites have shown the existence of differentiated genetic clusters within P. roqueforti, that are sympatric (Ropars et al 2014b;Gillot et al 2015). Ropars et al (2014) have revealed the existence of two main genetic clusters: the A cluster showed little diversity and contained only strains isolated from the cheese environment, whereas the B genetic cluster displayed higher genetic diversity and included strains from cheese and other environments.…”

The genomics of microbial domestication in the fermented food environment

“…To this end, extensive sampling combined with population genomic and phylogenomic approaches can be used to resolve the origin and number of domestication events [33,37,85,86]. Moreover, metagenomic sequencing of ecological niches that share (i) abiotic characteristics similar to the fermented food environment in question ( i.e.…”