Fungal Mycobiome of Mature Strawberry Fruits (Fragaria x ananassa Variety 'Monterey') Suggests a Potential Market Site Contamination with Harmful Yeasts

An amplicon metagenomic approach based on the ITS2 region of fungal rDNA was used to investigate the diversity of fungi associated with mature strawberries collected from a volcanic orchard and open-air market stands. Based on the Kruskal-Wallis test, no statistically significant differences were observed in both non-phylogenetic and phylogenetic alpha diversity indices. According to beta diversity analyses, significant differences in fungal communities were found between groups (orchard vs. market). Taxonomic assignment of amplicon sequence variables (ASVs) revealed 7 phyla and 31 classes. The prevalent fungal phyla were Basidiomycota (29.59-84.58%), Ascomycota (15.33-70.40%), and Fungi-phy-Insertae-sedis (0.45-2.89%). The most predominant classes among the groups were Saccharomycetes in the market group, and Microbotryomycetes and Tremellomycetes in the orchard group. Based on the analysis of microbiome composition (ANCOM), we found that the most differentially fungal genera were Hanseniaspora, Kurtzmaniella, and Phyllozyma. Endophytic yeasts Curvibasidium cygneicollum were prevalent in both groups, while Candida railenensis was detected in fruits originating only from the market. In addition, Rhodotorula graminis (relative abundance varying from 1.7% to 21.18%) and Papiliotrema flavescens (relative abundance varying from 1.58% to 16.55%) were detected in all samples regardless of origin, while Debaryomyces prosopidis was detected in samples from the market only, their relative abundance varying with the sample (from 0.80% to 19.23%). Their role in fruit quality and safety has not been yet documented. Moreover, several clinically related yeasts, such as Meyerozyma guilliermondii and Candida parapsilosis, were detected in samples only from the market. Understanding the variety and makeup of the mycobiome in ripe fruits during the transition from the orchard to the market is crucial for fruit safety after harvest.

Analysing indoor mycobiomes through a large-scale citizen science study in Norway

In the built environment, fungi can cause important deterioration of building materials and have adverse health effects on occupants. Increased knowledge about indoor mycobiomes from different regions of the world, and their main environmental determinants, will enable improved indoor air quality management and identification of health risks. This is the first citizen science study of indoor mycobiomes at a large geographical scale in Europe, including 271 houses from Norway and 807 dust samples from three house compartments: outside of the building, living room and bathroom. The fungal community composition determined by DNA metabarcoding was clearly different between indoor and outdoor samples, but there were no significant differences between the two indoor compartments. The 32 selected variables, related to the outdoor environment, building features and occupant characteristics, accounted for 15% of the overall variation in community composition, with the house compartment as the key factor (7.6%). Next, climate was the main driver of the dust mycobiomes (4.2%), while building and occupant variables had significant but minor influences (1.4% and 1.1%, respectively). The house-dust mycobiomes were dominated by ascomycetes (⁓70%) with Capnodiales and Eurotiales as the most abundant orders. Compared to the outdoor samples, the indoor mycobiomes showed higher species richness, which is probably due to the mixture of fungi from outdoor and indoor sources. The main indoor indicator fungi belonged to two ecological groups with allergenic potential: xerophilic moulds and skin-associated yeasts. Our results suggest that citizen science is a successful approach for unravelling the built microbiome at large geographical scales.