Großkopf, Regine;
Janssen, Peter H.;
Liesack, Werner
Diversity and Structure of the Methanogenic Community in Anoxic Rice Paddy Soil Microcosms as Examined by Cultivation and Direct 16S rRNA Gene Sequence Retrieval
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Medientyp:
E-Artikel
Titel:
Diversity and Structure of the Methanogenic Community in Anoxic Rice Paddy Soil Microcosms as Examined by Cultivation and Direct 16S rRNA Gene Sequence Retrieval
Beteiligte:
Großkopf, Regine;
Janssen, Peter H.;
Liesack, Werner
Erschienen:
American Society for Microbiology, 1998
Erschienen in:Applied and Environmental Microbiology
Beschreibung:
<jats:title>ABSTRACT</jats:title>
<jats:p>
A dual approach consisting of cultivation and molecular retrieval of partial archaeal 16S rRNA genes was carried out to characterize the diversity and structure of the methanogenic community inhabiting the anoxic bulk soil of flooded rice microcosms. The molecular approach identified four groups of known methanogens. Three environmental sequences clustered with
<jats:italic>Methanobacterium bryantii</jats:italic>
and
<jats:italic>Methanobacterium formicicum</jats:italic>
, six were closely related but not identical to those of strains of
<jats:italic>Methanosaeta concilii</jats:italic>
, two grouped with members of the genus
<jats:italic>Methanosarcina</jats:italic>
, and two were related to the methanogenic endosymbiont of
<jats:italic>Plagiopyla nasuta</jats:italic>
. The cultivation approach via most-probable-number counts with a subsample of the same soil as an inoculum yielded cell numbers of up to 10
<jats:sup>7</jats:sup>
per g of dry soil for the H
<jats:sub>2</jats:sub>
-CO
<jats:sub>2</jats:sub>
-utilizing methanogens and of up to 10
<jats:sup>6</jats:sup>
for the acetate-utilizing methanogens. Strain VeH52, isolated from the terminal positive dilution on H
<jats:sub>2</jats:sub>
-CO
<jats:sub>2</jats:sub>
, grouped within the phylogenetic radiation characterized by
<jats:italic>M. bryantii</jats:italic>
and
<jats:italic>M. formicicum</jats:italic>
and the environmental sequences of the
<jats:italic>Methanobacterium</jats:italic>
-like group. A consortium of two distinct methanogens grew in the terminal positive culture on acetate. These two organisms showed absolute 16S rRNA gene identities with environmental sequences of the novel
<jats:italic>Methanosaeta</jats:italic>
-like group and the
<jats:italic>Methanobacterium</jats:italic>
-like group.
<jats:italic>Methanosarcina</jats:italic>
spp. were identified only in the less-dilute levels of the same dilution series on acetate. These data correlate well with acetate concentrations of about 11 μM in the pore water of this rice paddy soil. These concentrations are too low for the growth of known
<jats:italic>Methanosarcina</jats:italic>
spp. but are at the acetate utilization threshold of
<jats:italic>Methanosaeta</jats:italic>
spp. Thus, our data indicated
<jats:italic>Methanosaeta</jats:italic>
spp. and
<jats:italic>Methanobacterium</jats:italic>
spp. to be the dominant methanogenic groups in the anoxic rice soil, whereas
<jats:italic>Methanosarcina</jats:italic>
spp. appeared to be less abundant.
</jats:p>