In this study, a series of laboratory experiments were designed to characterize the importance of mycoparasitism, exoenzymes, and volatile organic compounds (VOCs) by Trichoderma harzianum T-E5 for the control of Fusarium oxysporum f. sp. cucumerinum (FOC). We further tested whether these mechanisms were inducible and upregulated in presence Seliciclib of FOC. The results were as follows: T-E5 heavily parasitized FOC by coiling and twisting the entire mycelium of the pathogen in dual cultures. T-E5 growing medium conditioned with deactivated FOC (T2) showed more proteins and higher cell wall-degrading enzyme activities than T1, suggesting that FOC could induce the upregulation
of exoenzymes. The presence of deactivated FOC (T2′) also resulted in the upregulation of VOCs that five and eight different types T-E5-derived VOCs were identified from T1′ and T2′, respectively. Further, the excreted VOCs in T2′ showed significantly higher antifungal activities against FOC than T1′. In conclusion, mycoparasitism of T-E5 against FOC involved mycelium contact and the production of complex extracellular substances. Together, these data provide clues to help further clarify the interactions between these fungi. “
“The study of exopolysaccharide production by heterofermentative sourdough lactic acid bacteria has shown that Weissella strains isolated from
sourdoughs produce linear dextrans containing α-(16) glucose
residues with few Thymidylate synthase α-(13) linkages from sucrose. In this study, several dextran-producing strains, Weissella cibaria and Weissella confusa, isolated from sourdough, were click here characterized according to carbohydrate fermentation, repetitive element-PCR fingerprinting using (GTG)5 primers and glucansucrase activity (soluble or cell-associated). This study reports, for the first time, the characterization of dextransucrase from Weissella strains using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and in situ polymer production (after incubation with sucrose) from enzymatic fractions harvested from both sucrose and glucose culture media. Results demonstrate that dextransucrase activity was mainly soluble and associated with a constitutive 180-kDa protein. In addition, microsequencing of the active dextransucrase from W. cibaria LBAE-K39 allowed the design of specific primers that could detect the presence of glucansucrase encoding genes similar to GTFKg3 of Lactobacillus fermentum Kg3 and to DSRWC of W. cibaria CMU. This study hence indicates that sourdough Weissella strains synthesize original dextransucrase. Oligo- and homopolysaccharides produced from sucrose by lactic acid bacteria (LAB) have received increasing attention mainly because of their potential toward industrial applications such as texturizing agents and prebiotics (Naessens et al., 2005).