Elastic Properties of the Cell Wall of Aspergillus nidulans Studied with Atomic Force Microscopy
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- 作者：Liming Zhao ; David Schaefer ; Haixin Xu ; Swati J. Modi ; William R. LaCourse ; and Mark R. Marten
- 刊名：Biotechnology Progress
- 出版年：2005
- 出版时间：February 2005
- 年：2005
- 卷：21
- 期：1
- 页码：292 - 299
- 全文大小：269K
- 年卷期：v.21,no.1(February 2005)
- ISSN：1520-6033
文摘
Currently, little is known about the mechanical properties of filamentous fungalhyphae. To study this topic, atomic force microscopy (AFM) was used to measure cellwall mechanical properties of the model fungus Aspergillus nidulans. Wild type anda mutant strain (
csmA), lacking one of the chitin synthase genes, were grown inshake flasks. Hyphae were immobilized on polylysine-coated coverslips and AFM force-displacement curves were collected. When grown in complete medium, wild-typehyphae had a cell wall spring constant of 0.29 ± 0.02 N/m. When wild-type and mutanthyphae were grown in the same medium with added KCl (0.6 M), hyphae weresignificantly less rigid with spring constants of 0.17 ± 0.01 and 0.18 ± 0.02 N/m,respectively. Electron microscopy was used to measure the cell wall thickness andhyphal radius. By use of finite element analysis (FEMLAB v 3.0, Burlington, MA) tosimulate AFM indentation, the elastic modulus of wild-type hyphae grown in completemedium was determined to be 110 ± 10 MPa. This decreased to 64 ± 4 MPa for hyphaegrown in 0.6 M KCl, implying growth medium osmotic conditions have significanteffects on cell wall elasticity. Mutant hyphae grown in KCl-supplemented mediumwere found to have an elastic modulus of 67 ± 6 MPa. These values are comparablewith other microbial systems (e.g., yeast and bacteria). It was also found that underthese growth conditions axial variation in elastic modulus along fungal hyphae wassmall. To determine the relationship between composition and mechanical properties,cell wall composition was measured by anion-exchange liquid chromatography andpulsed electrochemical detection. Results show similar composition between wild-typeand mutant strains. Together, these data imply differences in mechanical propertiesmay be dependent on varying molecular structure of hyphal cell walls as opposed towall composition.
csmA), lacking one of the chitin synthase genes, were grown inshake flasks. Hyphae were immobilized on polylysine-coated coverslips and AFM force-displacement curves were collected. When grown in complete medium, wild-typehyphae had a cell wall spring constant of 0.29 ± 0.02 N/m. When wild-type and mutanthyphae were grown in the same medium with added KCl (0.6 M), hyphae weresignificantly less rigid with spring constants of 0.17 ± 0.01 and 0.18 ± 0.02 N/m,respectively. Electron microscopy was used to measure the cell wall thickness andhyphal radius. By use of finite element analysis (FEMLAB v 3.0, Burlington, MA) tosimulate AFM indentation, the elastic modulus of wild-type hyphae grown in completemedium was determined to be 110 ± 10 MPa. This decreased to 64 ± 4 MPa for hyphaegrown in 0.6 M KCl, implying growth medium osmotic conditions have significanteffects on cell wall elasticity. Mutant hyphae grown in KCl-supplemented mediumwere found to have an elastic modulus of 67 ± 6 MPa. These values are comparablewith other microbial systems (e.g., yeast and bacteria). It was also found that underthese growth conditions axial variation in elastic modulus along fungal hyphae wassmall. To determine the relationship between composition and mechanical properties,cell wall composition was measured by anion-exchange liquid chromatography andpulsed electrochemical detection. Results show similar composition between wild-typeand mutant strains. Together, these data imply differences in mechanical propertiesmay be dependent on varying molecular structure of hyphal cell walls as opposed towall composition.