Stress response in medically important Mucorales

Abstract

Mucorales are saprobes, ubiquitously distributed and able to infect a heterogeneous population of human hosts. The fungi require robust stress responses to survive in human host. We tested the growth of Mucorales in the presence of different abiotic stress. Eight pathogenic species of Mucorales, including Rhizopus arrhizus, Rhizopus microsporus, Rhizomucor pusillus, Apophysomyces elegans, Licthemia corymbifera, Cunninghamella bertholletiae, Syncephalastrum racemosum and Mucor racemosus, were exposed to different stress inducers: osmotic (sodium chloride and d-sorbitol), oxidative (hydrogen peroxide and menadione), pH, cell wall and metal ions (Cu, Zn, Fe and Mg). Wide variation in stress responses was noted: R. arrhizus showed maximum resistance to both osmotic and oxidative stresses, whereas R. pusillus and M. indicus were relatively sensitive. Rhizopus arrhizus and R. microsporus showed maximum resistance to alkaline pH, whereas C. bertholletiae, L. corymbifera, M. racemosus and A. elegans were resistant to acidic pH. Maximum tolerance was noted in R. microsporus to Cu, R. microsporus and R. arrhizus to Fe and C. bertholletiae to Zn. In contrast, L. corymbifera, A. elegans and M. indicus were sensitive to Cu, Zn and Fe respectively. In conclusion, R. arrhizus showed high stress tolerance in comparison to other species of Mucorales, and this could be the possible reason for high pathogenic potential of this fungi.

Pseudomonas aeruginosa inhibits Rhizopus microsporus germination through sequestration of free environmental iron

“…As fungal germination is dependent on environmental pH and nutrient availability 21,22 , we assessed whether the addition of the supernatant was inhibiting germination through modulation of these parameters. Addition of the bacterial supernatant to SAB broth resulted in mild alkalisation of the media (pH 7.33 vs. 6.45).…”

Efficacy of chemical disinfectants for the containment of the salamander chytrid fungus Batrachochytrium salamandrivorans

“…Enzymatic degradation of antimicrobial agents by means of catalases or peroxidases is a common strategy in pathogenic bacteria [34,35] and fungi [36,37]. Catalases are able to ‘detoxify’ H 2 O 2 by breakdown into H 2 O and O 2 , which is visualised by a bubbling reaction.…”

“…Although not yet explored, the pronounced catalase activity in Bsal may have implications for the host’s immune defences. Several pathogenic bacteria and fungi use catalases to neutralise the H 2 O 2 coming from phagocytes [34–37]. Evasion of defences allows these pathogens to survive in inflammatory foci (see e.g.…”

Pseudomonas aeruginosainhibitsRhizopus microsporusgermination through sequestration of free environmental iron

“…As fungal germination is dependent on environmental pH and nutrient availability (Buffo et al 1984; Singh et al 2016), we assessed whether the addition of the supernatant was inhibiting germination through modulation of these parameters. Addition of the bacterial supernatant to SAB broth resulted in mild alkalisation of the media (pH 7.33 vs. 6.45).…”