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Quantitative Monitoring of Mycelial Growth of Aspergillus fumigatus in Liquid Culture by Optical Density.

ABSTRACT: Filamentous fungi form multicellular hyphae, which generally form pellets in liquid shake cultures, during the vegetative growth stage. Because of these characteristics, growth-monitoring methods commonly used in bacteria and yeast have not been applied to filamentous fungi. We have recently revealed that the cell wall polysaccharide α-1,3-glucan and extracellular polysaccharide galactosaminogalactan (GAG) contribute to hyphal aggregation in Aspergillus oryzae. Here, we tested whether Aspergillus fumigatus shows dispersed growth in liquid media that can be quantitatively monitored, similar to that of yeasts. We constructed a double disruptant mutant of both the primary α-1,3-glucan synthase gene ags1 and the putative GAG synthase gene gtb3 in A. fumigatus AfS35 and found that the hyphae of this mutant were fully dispersed. Although the mutant lost α-1,3-glucan and GAG, its growth and susceptibility to antifungal agents were not different from those of the parental strain. Mycelial weight of the mutant in shake-flask cultures was proportional to optical density for at least 18 h. We were also able to quantify the dose response of hyphal growth to antifungal agents by measuring optical density. Overall, we established a convenient strategy to monitor A. fumigatus hyphal growth. Our method can be directly used for screening for novel antifungals against Aspergillus species. IMPORTANCE Filamentous fungi generally form hyphal pellets in liquid culture. This property prevents filamentous fungi so that we may apply the methods used for unicellular organisms such as yeast and bacteria. In the present study, by using the fungal pathogen Aspergillus fumigatus strain with modified hyphal surface polysaccharides, we succeeded in monitoring the hyphal growth quantitatively by optical density. The principle of this easy measurement by optical density could lead to a novel standard of hyphal quantification such as those that have been used for yeasts and bacteria. Dose response of hyphal growth by antifungal agents could also be monitored. This method could be useful for screening for novel antifungal reagents against Aspergillus species.

SUBMITTER: Miyazawa K

PROVIDER: S-EPMC8729762 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Aspergillus fumigatus is an opportunistic fungal pathogen of the lungs resulting in both chronic and acute infection. The fungus interacts with numerous bacteria that compose the microflora of the lung including Pseudomonas aeruginosa and Klebsiella pneumoniae, both common isolates from Cystic fibrosis sputum. It is well documented that bacterial and fungal interactions both physically and through production of secreted products which can alter the growth and virulence of other species. The interaction with P. aeruginosa has been characterised previously indicating decreased growth and increased gliotoxin production in the presence of cells and the opposite when only exposed to culture filtrate. In our analysis exposure of cell free culture filtrate inhibited fungal growth and increased gliotoxin production. This was supported with proteomic analysis indicating reduction in 1,3-beta-glucanosyltransferase (-3.97 fold), methyl sterol monooxygenase erg25B (-2.9 fold) and Calcium/calmodulin dependent protein kinase (-4.2 fold) involved in fungal development. Coupled with increased expression of Glutathione S-transferase gliG (6.17 fold), non-ribosomal peptide synthase gliP (3.67 fold), O-methyltransferase gliM (3.5 fold), Gamma-glutamyl acyltransferase gliK (2.89 fold) and thioredoxin reductase gliT (2.33 fold) involved in Gliotoxin production indicate a possible shift towards secondary metabolism. Qualitative proteomic analysis of the bacterial supernatant also elucidates possible mechanisms for these alterations including physical interaction by Outer membrane protein A, High-affinity zinc uptake system protein ZnuA and Iron uptake system component EfeO reducing essential nutrient availability, enzymatic activity including Periplasmic serine endoprotease DegP-like and redox active proteins including Alkyl hydroperoxide reductase C. These proteomic alterations to the fungus could have implications for the severity of virulence in the context of coinfection and may impact disease progression.

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Quantitative Monitoring of Mycelial Growth of Aspergillus fumigatus in Liquid Culture by Optical Density.

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