Moisture Influences Gene Expression and Allergens in Fungal Communities in House and ISS Dust

Ashleigh Bope, Nicholas Nastasi, Emma C. Hall, Bridget Hegarty, Rachel I. Adams, Allen Goldstein, Pawel K. Misztal, Karen C. Dannemiller, SARAH R. HAINES, University of Toronto

     Abstract Number: 343
     Working Group: Indoor Aerosols

Abstract
Microorganisms are found everywhere in our indoor environments, both in our buildings on Earth and on spacecraft such as the International Space Station (ISS). Fungal growth is limited by moisture availability with fungal growth increasing at elevated humidity conditions. Previous work has established a relationship between metabolic activity and moisture, however further work is needed to examine how microbial function in dust from both homes and the ISS are impacted by changes in moisture condition. A de novo metatranscriptome study was performed utilizing samples of dust from both homes and the ISS incubated at 50%, 85% or 100% equilibrium relative humidity (ERH) for a period of 7 - 14 days. Exposure of ISS dust to elevated humidity conditions (>80%) represents a simulated unexpected event such as a temporary ventilation system failure where relative humidity (RH) may increase above typical levels. In both ISS dust and Earth dust, transcription expression was tightly grouped by RH condition, meaning gene expression is likely a function of moisture availability. Additionally, in both ISS and Earth dust, genes associated with spore formation, germination and secondary metabolic processes were upregulated at elevated RH conditions. In Earth dust, toxin metabolic processes were upregulated at 100% ERH when compared to 50% ERH and genes for common mold species Aspergillus fumigatus and the Alt a 1 allergen from Alternaria alternata were expressed within the full transcriptome. Ultimately, metabolic activity of microbial communities found in dust on both Earth and the ISS were determined to be significantly impacted by variations in moisture conditions. Understanding how microbes react to increases in moisture will help us develop more robust microbial monitoring standards for spacecraft, and other indoor environments. Further work will explore the relationship between gene expression, allergens and toxins in our indoor environments.