Suppressive subtractive hybridization (SSH) is a technique
that can identify DNA segments, which are present
in one bacterial genome but absent from another
closely related genome or a group (Peng et al. 2011).
SSH is utilized to compare the genomic content of
closely related bacterial species. Strain-specific DNA
fragments can be isolated by this method and compared
to sequences of known genes or proteins, thus linking
functional data to unique DNA fragments within the
compared genomes. Galbraith et al. (2004) performed
SSH using total genomic DNA isolated from rumen
fluid samples of two hay-fed steers, arbitrarily designated
as tester or driver. A total of 96 subtraction DNA
fragments from the tester metagenome were amplified
and cloned, and the DNA sequences were determined.
Tester-specific SSH fragments were found in 95 of 96
randomly selected clones. DNA sequences analysis of
subtraction fragments revealed that large differences
exists in archaeal community structure between the rumen
of two steers fed identical diets and housed together.
In another study, Peng et al. (2011) developed and
validated a qPCR method based on a strain-specific
DNA fragment identified by SSH that has applications
in sensitive monitoring of Propionibacterium acidipropionici
P169 in both animal feed and rumen fluid.
Authors claimed that SSH-generated sequence can be
employed as a strain-specific molecular marker.