D. Guntli et al., Calystegine degradation capacities of microbial rhizosphere communities ofZea mays (calystegine-negative) and Calystegia sepium (calystegine-positive), FEMS MIC EC, 28(1), 1999, pp. 75-84
Calystegines are tropane alkaloids produced by the roots of a few plant spe
cies, A bioassay was developed to identify roots with a microbial rhizosphe
re community capable of calystegine degradation (i.e. MCD roots). In a fiel
d survey, the proportion of MCD roots of Zea mays (calystegine-negative) va
ried from 20 to 80%. In field experiments, the proportions of MCD roots of
Z. mays and Calystegia sepium (calystegine-positive) grown in a particular
plot were similar to each other but varied with time and, overall, were hig
her than those of Z. mays roots from adjacent plots free of C. sepium. In a
utoclaved soil, no root of C. sepium or Z. mays plants propagated as seeds
was MCD, indicating that calystegine-degrading microorganisms were not seed
-borne. However, MCD roots were found as early as I day after planting of r
hizomes of C. sepium in autoclaved soil or planting of axenic seedlings of
either plant in natural soil microcosms. In total, microorganisms capable o
f degrading calystegines were harboured not only in the rhizosphere of the
calystegine-producing plant but also in that of the calystegine-negative pl
ant and probably in bulk soil. (C) 1999 Federation of European Microbiologi
cal Societies. Published by Elsevier Science B.V. All rights reserved.