Abstract
Exopolymeric substances (EPS) can determine plant-microorganism interactions and have great potential as bioactive compounds. The different amounts of EPS obtained from cultures of three endophytic Fusarium culmorum strains with different aggressiveness—growth promoting (PGPF), deleterious (DRMO), and pathogenic towards cereal plants—depended on growth conditions. The EPS concentrations (under optimized culture conditions) were the lowest (0.2 g/L) in the PGPF, about three times higher in the DRMO, and five times higher in the pathogen culture. The EPS of these strains differed in the content of proteins, phenolic components, total sugars, glycosidic linkages, and sugar composition (glucose, mannose, galactose, and smaller quantities of arabinose, galactosamine, and glucosamine). The pathogen EPS exhibited the highest total sugar and mannose concentration. FTIR analysis confirmed the β configuration of the sugars. The EPS differed in the number and weight of polysaccharidic subfractions. The EPS of PGPF and DRMO had two subfractions and the pathogen EPS exhibited a subfraction with the lowest weight (5 kDa). The three EPS preparations (ethanol-precipitated EP, crude C, and proteolysed P) had antioxidant activity (particularly high for the EP-EPS soluble in high concentrations). The EP-EPS of the PGPF strain had the highest antioxidant activity, most likely associated with the highest content of phenolic compounds in this EPS.
Highlights
Microbial polymeric substances (PS) have been studied for decades due to their interesting properties and novel functionality, which is not found in polymers produced by other organismsMolecules 2020, 25, 616; doi:10.3390/molecules25030616 www.mdpi.com/journal/moleculesMolecules 2020, 25, 616 like algae or plants [1,2,3,4,5,6]
The aim of the study was to compare production of exopolymers by three Fusarium culmorum The aim of the study was to compare production of exopolymers by three Fusarium culmorum strains exerting different effects on plants —a deleterious rhizosphere microorganisms (DRMO), a plant growth promoting fungi (PGPF) and a pathogenic one—and to strains exerting different effects on plants —a DRMO, a PGPF and a pathogenic one—and to determine determine the differences between the Exopolymeric substances (EPS) obtained from culture of these strains, with particular the differences between the EPS obtained from culture of these strains, with particular emphasis on emphasis on their biochemical properties, composition, and dissolution and antioxidant ability
The monosaccharide composition of F. culmorum EPS was studied in the present work for EPS obtained in cultures of three strains of F. culmorum on a medium with a C:N ratio of 6
Summary
Microbial polymeric substances (PS) have been studied for decades due to their interesting properties and novel functionality, which is not found in polymers produced by other organismsMolecules 2020, 25, 616; doi:10.3390/molecules25030616 www.mdpi.com/journal/moleculesMolecules 2020, 25, 616 like algae or plants [1,2,3,4,5,6]. Polymers of microbial origin are commonly found in various natural environments (soils, waters, and air) [2,7,8]. These polymers, which are usually the main constituent of biofilms, enable microorganisms to colonize, adapt, and thrive in new ecological niches and under extreme physical, chemical, and biological (antagonistic micro- and macroorganisms and defense responses of plant or animal hosts) conditions [9,10,11]. While information on lighting conditions appears in studies on the production of EPS in algal cultures [12,13] and in few reports on bacteria of the genus.
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