EFFECTS OF NON-LETHAL CONCENTRATIONS OF BIOACTIVE COMPOUNDS ON PLANT-RELATED BIOFILMS
Tesi di Dottorato
Data di Pubblicazione:
2018
Citazione:
EFFECTS OF NON-LETHAL CONCENTRATIONS OF BIOACTIVE COMPOUNDS ON PLANT-RELATED BIOFILMS / L. De Vincenti ; tutors: Cappitelli F., Forlani F. ; coordinatore: Bonomi F., Pagliarini E. ; tutors esterni: De La Fuente L., Papenbrock J.. DIPARTIMENTO DI SCIENZE PER GLI ALIMENTI, LA NUTRIZIONE E L'AMBIENTE, 2018 Dec 18. 31. ciclo, Anno Accademico 2018. [10.13130/de-vincenti-luca_phd2018-12-18].
Abstract:
It has been estimated that at least 99 % of the world’s microbial biomass exists in form of biofilm, a complex differentiated surface-associated community embedded in a self-produced polymeric matrix enabling microorganisms to develop coordinated and efficient survival strategies. Biofilm formation is a dynamic and cyclical process involving attachment, maturation and a final dispersal phase, and these steps are initiated by a variety of signals. Despite their positive effects in some cases, biofilms can be detrimental in different environmental domains since microorganisms are able to colonize almost all types of surfaces both abiotic and biotic, leading to consequences in terms of social and economic impact. These include human tissues, implantable medical devices, natural aquatic systems, plants, food and industrial lines. Once biofilm is formed, its eradication becomes difficult because its resilience to environmental stresses, disinfectants, and antimicrobial treatments.
Plants support a diverse array of microorganisms that exist in form of biofilms. Even if in some cases the association with plants leads to beneficial interactions promoting plant growth, inducing plant defense mechanisms and preventing the deleterious effects of pathogenic microorganisms, in other cases they have a significant negative impact. For instance, in agriculture, plant colonization of fungi and bacteria in form of biofilm is a cause of plant diseases, affecting crop quality and productivity. Indeed, despite the planktonic growth, biofilm lifestyle improves microbial resistance to antimicrobials up to several orders of magnitude, often reducing the possibility of treating biofilm effectively. In addition, due to the worrisome consequences related to the use of these substances on human health and on their persistence in the environment, increasingly regulations are arising to limit antimicrobial application. Furthermore, in addition to the principles of integrated pest management (IPM) embraced by the worldwide legislation aims to recommend alternative approaches to the application of pesticides, an innovative approach could be the use of biocide-free bioactive compounds characterized by novel targets, unique modes of action and properties that are separate from those currently highlighted in the use of antimicrobials. Indeed, the application of non-lethal doses of bio-inspired molecules able to interfere with specific key-steps involved in the biofilm formation process has been suggested as a complementary/alternative strategy to hinder biofilm formation. In addition, this approach also lead to deprive microorganisms of their virulence factors without affecting their viability and decreasing the selection pressure for biocides resistance. In this PhD thesis, the in vitro effects of non-lethal concentrations of several bioactive compounds were evaluated on the biofilm formation of different plant-associated microorganisms. Specifically, the aim of this work was to provide new effective preventive or integrated solutions against bacterial and fungal biofilm formation.
In chapter III, the methanol extracts obtained by different plant portions of three seagrass species collected in Vietnam and in India (Enhalus acoroides, Halophila ovalis and Halodule pinifolia) were investigated for their effects in mediating non-lethal interactions on sessile Escherichia coli and Candida albicans cultures taken as models of bacterial and fungal biofilms respectively. The study was focused on anti-biofilm activities of seagrass extracts, without killing cells. Seagrass extracts appeared to be more effective in deterring microbial adhesion on hydrophobic surfaces than on hydrophilic. Results revealed that E. acoroides leaf extract proved to be the most promising ex
Tipologia IRIS:
Tesi di dottorato
Keywords:
Plant-associated biofilm; bio-inspired compounds; non-lethal concentrations; anti-biofilm strategies
Elenco autori:
L. DE VINCENTI
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