Effect of low shear modeled microgravity on phenotypic and central chitin metabolism in the filamentous fungi Aspergillus niger and Penicillium chrysogenum

Phenotypic and genotypic changes in Aspergillus niger and Penicillium chrysogenum, spore forming filamentous fungi, with respect to central chitin metabolism were studied under low shear modeled microgravity, normal gravity and static conditions. Low shear modeled microgravity (LSMMG) response showed a similar spore germination rate with normal
gravity and static conditions. Interestingly, high ratio of
multiple germ tube formation of A. niger in LSMMG
condition was observed. Confocal laser scanning
microscopy images of calcofluor flurophore stained A.
niger and P. chrysogenum showed no significant
variations between different conditions tested. Transmission electron microscopy images revealed number
of mitochondria increased in P. chrysogenum in low
shear modeled microgravity condition but no stress
related-woronin bodies in fungal hyphae were observed.
To gain additional insight into the cell wall integrity
under different conditions, transcription level of a key
gene involved in cell wall integrity gfaA, encoding the
glutamine: fructose-6-phosphate amidotransferase
enzyme, was evaluated using qRT-PCR. The transcription level showed no variation among different conditions. Overall, the results collectively indicate that the LSMMG has shown no significant stress on spore germination, mycelial growth, cell wall integrity of potentially pathogenic fungi, A. niger and P.chrysogenum.