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Appl. Environ. Microbiol., Apr 1997, 1199-1207, Vol 63, No. 4
U Bosse and P Frenzel
The activity and distribution of CH(inf4)-oxidizing bacteria (MOB) in
flooded rice (Oryza sativa) soil microcosms was investigated. CH(inf4)
oxidation was shown to occur in undisturbed microcosms by using
(sup14)CH(inf4), and model calculations indicated that almost 90% of the
oxidation measured had taken place at a depth where only roots could
provide the O(inf2) necessary. Slurry from soil planted with rice had an
apparent K(infm) for CH(inf4) of 4 (mu)M and a V(infmax) of 0.1 (mu)mol g
(dry weight)(sup-1) h(sup-1). At a depth of 1 to 2 cm, there was no
significant difference (P > 0.05) in numbers of MOB between soil from
planted and nonplanted microcosms (mean, 7.7 x 10(sup5) g [fresh
weight](sup-1)). Thus, the densely rooted soil at 1 to 2 cm deep did not
represent rhizospheric soil with respect to the number of MOB. A
significantly increased number of MOB was found only in soil immediately
around the roots (1.2 x 10(sup6) g [fresh weight](sup-1)), corresponding to
a layer of 0.1 to 0.2 mm. Plant-associated CH(inf4) oxidation was shown in
a double chamber with carefully washed intact rice plants. Up to 90% of the
CH(inf4) supplied to the root compartment was oxidized in the plants.
CH(inf4) oxidation on isolated roots was higher and had a larger
variability than that in soil slurries. Roots had an apparent K(infm) for
CH(inf4) of 6 (mu)M and a V(infmax) of 5 (mu)mol g (dry weight)(sup-1)
h(sup-1). The average number of MOB in homogenized roots was larger than on
the rhizoplane and increased with plant age. MOB also were found in
surface-sterilized roots and basal culms, indicating the ability of these
bacteria to colonize the interior of roots and culms.
Copyright © 1997, American Society for Microbiology
Activity and Distribution of Methane-Oxidizing Bacteria in Flooded Rice Soil Microcosms and in Rice Plants (Oryza sativa)
Max-Planck-Institut fur Terrestrische Mikrobiologie, D-35043 Marburg, Germany
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