Proprietà filmogene del fungo Pleurotus ostreatus: produzione, caratterizzazione e risposta a contaminanti ambientali
Author(s)
Pesciaroli, Lorena
Date Issued
June 10, 2013
Type
Doctoral Thesis
Abstract
In nature, microorganisms are seldom found in planktonic form; rather, they tend to interact with solid matrices and other microbes so as to develop complex systems named ‘biofilms’. Although filamentous fungi are ideal biofilm-forming candidates, there is scant information regarding this topic. The biofilm-forming properties of the fungus Pleurotus ostreatus, alone or in association with bacteria has been reported. However, no basic information is currently available on structural and physiological properties of P. ostreatus-based biofilm systems. In fact, the general aim of this thesis was to gain insights into P. ostreatus biofilm production, its biochemical and structural characterization and response to environmental contaminants. In particular, the biofilm-forming properties of P. ostreatus were evaluated using two different methodological approaches that allowed to obtain P. ostreatus biofilms that fully met the structural and phenotypic criteria suggested by Harding et al. (2009) for fungal biofilm. The first approach involved the use of 12-well plates hosting circular membranes made of various materials as the adhesion supports. In this way, it was possible to elucidate the effect of support and growth medium on production, specific metabolic activity and ultrastructure of P. ostreatus biofilm. Hydrophilic and mild hydrophobic supports were more adequate for biofilm production than highly hydrophobic supports, such as Teflon, while the biofilm ultrastructure was more significantly affected by growth media than support type. The main effects of support and growth media variables and their binary interactions on both biofilm production and specific metabolic activity were all highly significant (P< 0.001); thus, the effect of each variable strongly depended on the level of the other one.
The second methodological approach, instead, relied on the use of MBECTM-P&G and MBECTM-HTP systems, that had been extensively used for the study of bacterial and yeast biofilms. With the former configuration, significant biofilm amounts were produced and an even distribution of biofilm was observed regardless of the incubation time. In the MBECTM-HTP, instead, both amounts and spatial uniformity of P. ostreatus biofilms were markedly affected by the incubation conditions. Both chemical analyses and electron microscopy observations showed that biofilm cultures were characterized by higher amounts of ECM than planktonic system.
Cadmium and phenol compounds in olive mill wastewater were chosen as environmental contaminants to evaluate comparatively the response of P. ostreatus biofilm and planktonic cultures.
P. ostreatus biofilms exhibited a significantly higher tolerance to cadmium and a higher efficiency in olive-mill wastewater treatment than coeval planktonic cultures.
In nature, commonly, biofilms are concomitantly composed of bacteria and fungi and this is important in bioremediation processes and in agricultural applications. In fact, another aim of this thesis was study the biofilm formation of P. ostreatus and Pseudomonas alcaliphila. In the mixed biofilm systems, P. alcaliphila predominated over the fungus due to its higher growth rate as assessed by both quantitative PCR and electron microscopy analyses.
Additional information
Dottorato di ricerca in Evoluzione biologica e biochimica
Subjects
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