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Appl. Environ. Microbiol., Feb 1996, 316-322, Vol 62, No. 2
J Zhou, MA Bruns and JM Tiedje
A simple, rapid method for bacterial lysis and direct extraction of DNA
from soils with minimal shearing was developed to address the risk of
chimera formation from small template DNA during subsequent PCR. The method
was based on lysis with a high-salt extraction buffer (1.5 M NaCl) and
extended heating (2 to 3 h) of the soil suspension in the presence of
sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide, and
proteinase K. The extraction method required 6 h and was tested on eight
soils differing in organic carbon, clay content, and pH, including ones
from which DNA extraction is difficult. The DNA fragment size in crude
extracts from all soils was > 23 kb. Preliminary trials indicated that
DNA recovery from two soils seeded with gram- negative bacteria was 92 to
99%. When the method was tested on all eight unseeded soils, microscopic
examination of indigenous bacteria in soil pellets before and after
extraction showed variable cell lysis efficiency (26 to 92%). Crude DNA
yields from the eight soils ranged from 2.5 to 26.9 micrograms of DNA g-1,
and these were positively correlated with the organic carbon content in the
soil (r = 0.73). DNA yields from gram-positive bacteria from pure cultures
were two to six times higher when the high-salt-SDS-heat method was
combined with mortar-and-pestle grinding and freeze-thawing, and most DNA
recovered was of high molecular weight. Four methods for purifying crude
DNA were also evaluated for percent recovery, fragment size, speed, enzyme
restriction, PCR amplification, and DNA-DNA hybridization. In general, all
methods produced DNA pure enough for PCR amplification. Since soil type and
microbial community characteristics will influence DNA recovery, this study
provides guidance for choosing appropriate extraction and purification
methods on the basis of experimental goals.
Copyright © 1996, American Society for Microbiology
DNA recovery from soils of diverse composition
Center for Microbial Ecologia, Michigan State University, East Lansing, 48824-1325, USA.
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