The symbiotic phenotypes of exopolysaccharide-defective mutants of Rhizobium sp. strain TAL1145 do not differ on determinate- and indeterminate-nodulating tree legumes

摘要: Three classes of exopolysaccharide (EPS) defective mutants were isolated by Tn3Hogus-insertion mutagenesis Rhizobium sp. strain TAL1145, which nodulates tree legumes. The class I and III produced 10-22% the EPS TAL1145 appeared partially mucoid while II formed small, opaque non-mucoid colonies. Size-fractionation soluble EPSs made these in culture supernatant indicated that reduced levels both highland low-molecular-mass lacked but a small amount medium-molecular-mass anthrone-reactive EPS. succinyl acetyl substituents observed absent mutants. When examined under UV, grown on Calcofluor-containing YEM agar showed dim blue fluorescence, compared to bright fluorescence wild-type strain, whereas did not fluoresce. While changed yellow-green after 10 d, change prolonged incubation. Unlike EPS-defective other rhizobia, show different symbiotic phenotypes determinate- indeterminate-nodulating ineffective nodules types legumes normal nitrogen-fixing types. genes disrupted form single complementation group those constitute another. All three located within 10.8 kb region complemented two overlapping cosmids.