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POSTERS: Biological control

Effects of chitin on antibiotic and lytic enzyme gene expression by the biocontrol bacterium Lysobacter enzymogenes
Dongxue Shi - University of Nebraska-Lincoln. Gary Yuen- University of Nebraska-Lincoln

Lysobacter enzymogenes C3 is a biocontrol agent that can inhibit fungal diseases by producing beta-1,3-glucanases, chitinases, and the antibiotic HSAF. Lytic enzyme production by C3 can be enhanced by supplying chitin, but the influence of chitin on HSAF production is unknown. Previously, we used qRT-PCR to demonstrate that the PKS-NRPS gene (PKS) essential for HSAF synthesis and the structural genes for glucanase C (gluC) and chitinase A (chiA) are expressed by C3 in soybean rhizospheres at different levels and times following C3 seed treatment. One objective of this study was to determine the effects of chitin on antibiotic and lytic enzyme gene expression by C3 in vitro. When cultured in a chitin-supplemented mineral salts medium, C3 exhibited peak expression of chiA and gluC after 24 hours, while high PKS gene expression occurred at 12 hours. Another objective was to determine if soil amendment with chitin can affect the expression of antibiotic and lytic enzyme genes by C3 in bulk soil and in soybean roots. C3 in soil expressed PKS, chiA, and gluC when chitin was added but not when chitin was withheld. In contrast, chitin soil amendment caused little or no change in gene expression by C3 in roots compared with no chitin amendment. Our results suggest that in nutrient-deficient environments such as bulk soil, C3 expression of biocontrol genes is highly responsive to the addition of chitin, whereas in the rhizosphere, exogenous chitin has a lesser effect on gene expression by C3.