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Applied and Environmental Microbiology, April 1999, p. 1662-1669, Vol. 65, No. 4
Environmental Molecular Biology Group, Life
Sciences Division, Los Alamos National Laboratory, Los Alamos, New
Mexico 87545
Received 4 September 1998/Accepted 4 January 1999
Techniques based on amplification of 16S rRNA genes for comparing
bacterial communities are now widely used in microbial ecology, but
calibration of these techniques with traditional tools, such as
cultivation, has been conspicuously absent. In this study, we compared
levels of bacterial community diversity in two pinyon rhizosphere soil
samples and two between-tree (interspace) soil samples by analyzing 179 cultivated bacterial isolates and 801 16S rRNA genes amplified from
extracted soil DNA. Phylotypes were defined by performing a restriction
fragment length polymorphism analysis of 16S rRNA gene sequences with
the enzymes RsaI and BstUI. The average level
of 16S rRNA gene sequence similarity of members of a phylotype was
86.6% based on an analysis of partial sequences. A total of 498 phylotypes were identified among the 16S ribosomal DNA (rDNA) clones,
while 34 phylotypes occurred among the cultivated isolates. Analysis of
sequences from a subset of the phylotypes showed that at least seven
bacterial divisions were represented in the clone libraries, whereas
the isolates represented only three. The phylotype richness, frequency
distribution (evenness), and composition of the four culture
collections and the four clone libraries were investigated by using a
variety of diversity indices. Although cultivation and 16S rRNA cloning analyses gave contradictory descriptions of the relative phylotype richness for one of the four environments, the two methods identified qualitatively consistent relationships when levels of evenness were
compared. The levels of phylotype similarity between communities were
uniformly low (15 to 31%). Both methods consistently indicated that
one environment was distinct from the other three. Our data illustrate
that while 16S rDNA cloning and cultivation generally describe similar
relationships between soil microbial communities, significant
discrepancies can occur.
0099-2240/99/$04.00+0
Levels of Bacterial Community Diversity in Four
Arid Soils Compared by Cultivation and 16S rRNA Gene Cloning
*
Corresponding author. Mailing address: Environmental
Molecular Biology Group, M888, Life Sciences Division, Los Alamos
National Laboratory, Los Alamos, NM 87545. Phone: (505) 665-4800. Fax: (505) 665-3024. E-mail: kuske{at}lanl.gov.
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