Melinacidin-Producing Acrostalagmus luteoalbus, a Major Constituent of Mixed Mycobiota Contaminating Insulation Material in an Outdoor Wall.

(Aino) Maria A Andersson,Raimo Mikkola,Tamás Marik,Heidi Salonen,Johanna Salo,Jarek Kurnitski,László Kredics

doi:10.3390/pathogens10070843

Abstract

Occupants may complain about indoor air quality in closed spaces where the officially approved standard methods for indoor air quality risk assessment fail to reveal the cause of the problem. This study describes a rare genus not previously detected in Finnish buildings, Acrostalagmus, and its species A. luteoalbus as the major constituents of the mixed microbiota in the wet cork liner from an outdoor wall. Representatives of the genus were also present in the settled dust in offices where occupants suffered from symptoms related to the indoor air. One strain, POB8, was identified as A. luteoalbus by ITS sequencing. The strain produced the immunosuppressive and cytotoxic melinacidins II, III, and IV, as evidenced by mass spectrometry analysis. In addition, the classical toxigenic species indicating water damage, mycoparasitic Trichoderma, Aspergillus section Versicolores, Aspergillus section Circumdati, Aspergillus section Nigri, and Chaetomium spp., were detected in the wet outdoor wall and settled dust from the problematic rooms. The offices exhibited no visible signs of microbial growth, and the airborne load of microbial conidia was too low to explain the reported symptoms. In conclusion, we suggest the possible migration of microbial bioactive metabolites from the wet outdoor wall into indoor spaces as a plausible explanation for the reported complaints.

Highlights

The term “microbiota” refers to the microbial community in a defined environment
A building inspection revealed that the outdoor wall outside the problematic rooms was damaged and that rainwater had penetrated into the wall structure
A cork liner used as isolation inside the plinth in the outer wall was moist and degraded by microbes

Summary

Introduction

The term “microbiota” refers to the microbial community in a defined environment. The term “microbiome” refers to the total genome of such microbiota. The colonizing microbiota and the microbiome are global and uniform compared to those outdoors, which are local and diverse [1,2]. In urban environments in high-income countries, the major microbial exposure by humans over their lifetime is to uniform building microbiota [3,4,5]. An indoor lifestyle leaves occupants at the mercy of uniform building microbiota, where microbial exposomes trapped indoors can reach higher concentrations and persist longer than those outdoors [1,3,6,7,8]. Microbes including Aspergillus, Penicillium, Trichoderma, Fusarium, Chaetomium, Streptomyces, Bacillus, and Nocardiopsis species, which produce bioreactive metabolites such as mycotoxins [9,10,11,12,13,14,15], immunoreactive substances [16,17,18], mitochondrial and ionophoric toxins, and fungicides and antibiotics, contribute to the building exposome in wet buildings worldwide [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33]

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Results