Cell-wall structure and composition ofPenicillium janczewskiias affected by inulin

Abstract

Penicillium janczewskii, a filamentous fungus isolated from the rhizosphere of Vernonia herbacea (Asteraceae), grows rapidly on media containing either sucrose or inulin as carbon sources. Maintenance of P. janczewskii on inulin medium induces secretion of proteins with high inulinase activity but results in a mycelium that easily collapses and breaks. We evaluated the influence of inulin on fungal growth and colony morphology and on cell-wall structure and composition in comparison with growth and wall characteristics on sucrose-containing medium. P. janczewskii grown on Czapek medium with agar containing 1% (w/v) sucrose or inulin showed differences in the color and morphology of the colonies, although growth rates were similar on both carbon sources. Scanning-electron microscopy revealed that the hyphae from fungus grown on inulin-containing medium are much thinner than those from fungus cultivated on sucrose. Ultrastructural analysis of 5 d old cultures using transmission-electron microscopy indicated significant differences in the cell-wall thickness between hyphae grown on inulin or sucrose media. No differences were detected in the overall carbohydrate and protein contents of cell walls isolated from cultures grown on the two carbon sources. Glycosyl composition analyses showed glucose and galactose as the predominant neutral monosaccharides in the walls but showed no differences attributable to the carbon source. Glycosyl linkage composition analyses indicated a predominance of 3-linked glucopyranosyl in the hyphal walls when P. janczewskii was grown on inulin-containing medium. Our results suggest that growth on inulin as the sole carbon source results in structural changes in the mycelia of P. janczewskii that lead to mycelial walls with altered physical and biological properties.

Fructose affecting morphology and inducing β-fructofuranosidases in Penicillium janczewskii

“…Our findings provide evidences that fructose-containing sugars supplied as carbon source directly affect the cell metabolism of P. janczewskii thus explaining our previous results (Pessoni et al 2005 ) on cell wall alteration when this fungus is cultured on inulin to induce extracellular inulinases.…”

“…Ruiz-Herrera ( 1992 ) observed that factors such as nutrition, temperature and incubation time cause significant differences in fungal cell walls. The same was also observed in Penicillium janczewskii that grows rapidly on medium containing sucrose or inulin as carbon sources, but only in inulin-containing medium large amounts of inulinases (2,1-β- d -fructan:fructan hydrolase EC 3.2.1.7) were released, which was associated with thin cell walls (Pessoni et al 2005 ). Considering that inulin is a polymer of fructose, it was hypothesized that high fructose content in the medium as a result of the released extracellular inulinases could be involved in the morphological changes observed in the hyphae cell walls.…”

“…The maintenance of P. janczewskii in the inulin-containing medium induces secretion of large amounts of inulinases but results in hyphae with thin cell walls that easily collapses and breaks; the same was not observed when the fungus was cultured in medium containing sucrose (Pessoni et al 2005 ). Although no differences were found in content of sugars and proteins from the cell wall of hyphae grown on these carbon sources, a significant decrease in cell wall thickness was observed when the fungus was grown on inulin (Pessoni et al 2005 ). In the present work it was observed that although the growth rate of P. janczewskii in solid medium containing fructose was similar to those found in other media (Figs.…”

“…The growth curve of P. janczewskii was determined as described by Pessoni et al ( 2005 ). Inocula of 5 mm in diameter obtained from pure cultures grown for 7 days on PDA were placed in the center of Petri dishes containing the culture media described above.…”

Adsorption Behavior of Mercury on Functionalized Aspergillus versicolor Mycelia: Atomic Force Microscopic Study

“…We compared the elasticity of A. versicolor mycelia with other biological materials adopting similar model. The cell wall of A. versicolor is stiffer than the phospholipid vesicles (∼2 MPa) but lower than that of A. nidulans reported by Zhao et al and Ma et al The lower elasticity of A. versicolor compared to that of A. nidulans may be due to the variation of cell wall constituents (β-1,3- d -glucans, mannans, chitin, and chitosan, as well as glycoproteins and lipids). , It is suggested that the polysaccharide composition of A. versicolor differs considerably from that of A. nidulans ; consequently, considerable difference in the cell wall elasticity is observed. On xanthate functionalization, the cell wall rigidity and elasticity increased significantly ( p < 0.1) to 0.88 ± 0.05 N/m and 92.6 ± 10.2 MPa, respectively, from 0.65 ± 0.05 N/m and 32.8 ± 4.5 MPa of the corresponding pristine mycelia.…”