Abstract
White-nose Syndrome (WNS) is an emerging infectious mycosis that has impacted multiple species of North American bats since its initial discovery in 2006, yet the physiology of the causal agent, the psychrophilic fungus Pseudogymnoascus destructans ( = Geomyces destructans), is not well understood. We investigated the ability of P. destructans to secrete enzymes that could permit environmental growth or affect pathogenesis and compared enzyme activity across several Pseudogymnoascus species isolated from both hibernating bats and cave sediments. We found that P. destructans produced enzymes that could be beneficial in either a pathogenic or saprotrophic context, such as lipases, hemolysins, and urease, as well as chitinase and cellulases, which could aid in saprotrophic growth. The WNS pathogen showed significantly lower activity for urease and endoglucanase compared to con-generic species (Pseudogymnoascus), which may indicate a shift in selective pressure to the detriment of P. destructans’ saprotrophic ability. Based on the positive function of multiple saprotrophic enzymes, the causal agent of White-nose Syndrome shows potential for environmental growth on a variety of substrates found in caves, albeit at a reduced level compared to environmental strains. Our data suggest that if P. destructans emerged as an opportunistic infection from an environmental source, co-evolution with its host may have led to a reduced capacity for saprotrophic growth.
Highlights
White-nose Syndrome is a fungal disease that has killed millions of hibernating bats in North America since its discovery in 2006 [1,2]
The causal agent of White-nose Syndrome (WNS) was identified as a novel fungal pathogen, Geomyces destructans [1,3,4], which was recently reclassified into the genus Pseudogymnoascus (Pseudeurotiaceae, incertae sedis, Leotiomycetes) [5]
Based on the phylogeny for our Pseudogymnoascus strains, two genetically diverse subsets of Pseudogymnoascus spp were selected for physiological tests: (1) a set of six Pseudogymnoascus spp. representing five clades, including four of our isolates (BL308, BL549, BL578 and BL606), P. destructans, the control species P. pannorum, Penicillium pinophilum, and O. maius; and (2) a set of eight isolates from bat fur and cave sediments representing eight additional Pseudogymnoascus lineages (13PA1 to FI698) used in triplicate tests
Summary
White-nose Syndrome is a fungal disease that has killed millions of hibernating bats in North America since its discovery in 2006 [1,2]. Lorch et al 2013 [13] found Pd DNA and viable Pd spores in cave sediments after the departure of the WNS-infected bat hosts; it is unknown whether the presence of Pd in these sediments is due to environmental propagation or to the persistence of spores shed from infected hosts. If the latter were the case, an obligate bat pathogen would be limited to growth in the hibernation season when bat body temperatures during torpor permit fungal growth, reducing the likelihood of environmental spread
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