Most of the nucleic acid methods use molecular
hybridization properties, which involve the complementary
sequence recognition between a nucleic probe and a nucleic target. A hybridization reaction
can be realized between a nucleic DNA probe and a
chromosomic DNA sequence (DNA–DNA hybridization)
or an rRNA or tRNA sequence (DNA–RNA
hybridization). Specificity, here, depends on the phylogenetic
degree of conservation of the target within
the taxonomic target group. These methods offer
taxonomic information at different levels, such as
classes, genera, species or subspecies. Some of them
can be performed without the need for a complex
cultivation step, thereby permitting the detection of
specific bacteria within hours, instead of few days
required with the cultivation-based methods. The
more frequently used nucleic-acid-based methods are
the polymerase chain reaction (PCR) and the in situ
hybridization (ISH) methods. Assessment of their
performance in the detection of coliforms in drinking
water samples is discussed below.
Most of the nucleic acid methods use molecularhybridization properties, which involve the complementarysequence recognition between a nucleic probe and a nucleic target. A hybridization reactioncan be realized between a nucleic DNA probe and achromosomic DNA sequence (DNA–DNA hybridization)or an rRNA or tRNA sequence (DNA–RNAhybridization). Specificity, here, depends on the phylogeneticdegree of conservation of the target withinthe taxonomic target group. These methods offertaxonomic information at different levels, such asclasses, genera, species or subspecies. Some of themcan be performed without the need for a complexcultivation step, thereby permitting the detection ofspecific bacteria within hours, instead of few daysrequired with the cultivation-based methods. Themore frequently used nucleic-acid-based methods arethe polymerase chain reaction (PCR) and the in situhybridization (ISH) methods. Assessment of theirperformance in the detection of coliforms in drinkingwater samples is discussed below.
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