Multi-omic characterization of Aspergillus fumigatus isolated from air and surfaces of the International Space Station

Adriana Blachowicz blachowi@usc.edu ^1,2 Benjamin P. Knox ³ Jillian Romsdahl ¹ Jonathan M. Palmer ⁴ Abby Chiang ⁵ Markus Kalkum ⁵ Anna Huttenlocher ³ Nancy P. Keller ³ Kasthuri Venkateswaran ² Clay C.C. Wang ^1,6

¹Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California, USA
²Biotechnology and Planetary Protection Group, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
³Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
⁴Center for Forest Mycology Research, US Forest Service, Madison, Wisconsin, USA
⁵Department of Molecular Immunology, Beckman Research Institute of City of Hope, Duarte, California, USA
⁶Department of Chemistry, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California, USA

The on-going Microbial Observatory Experiments on the International Space Station (ISS) revealed the presence of various microorganisms that may be affected by the distinct environment of the ISS. The low-nutrient environment combined with enhanced radiation and microgravity may trigger changes in the molecular, genetic and biochemical suit of microbes and lead to increased virulence and resistance of originally harmless microbes. Additionally, such an environment may trigger the production of bioactive compounds. So far, the majority of carried out studies have focused on bacteria, and filamentous fungi aboard the ISS have been generally understudied.

Two ISS-isolates were identified as Aspergillus fumigatus, which is known to be an opportunistic pathogen, and therefore may be potentially harmful for astronauts’ health whose immune systems are reported to be compromised under microgravity. Whole genome sequence analysis of both isolates revealed 54,960 and 52,129 single nucleotide polymorphisms (SNPs) when compared to the clinical reference strain, Af293, which is consistent with the genetic heterogeneity amongst sequenced A. fumigatus strains from an array of clinical and environmental sources. Secondary metabolite (SM) profiles of both ISS isolates were compared to the reference (Af293). Additionally, ISS-isolated A. fumigatus strains showed enhanced UVC resistance and increased virulence, possibly in response to the unique environment of the ISS (enhanced radiation, microgravity, low-nutrients), when compared to clinical isolates. In-depth analysis of proteome changes between clinical and ISS-isolated strains revealed differential expression of unique proteins involved in stress response, carbohydrate metabolic processes, pathogenesis and secondary metabolism.

Complex analyses of possible molecular alterations triggered by microgravity and enhanced radiation will be pertinent to the future long-term manned space flights, as such an understanding is crucial for astronauts’ health and maintenance of the closed habitat.