Prof. Mahmoud Abd El Mohsen Swelim :: Publications:

Intraspecific variation in the 16s rRNA genes of three Escherichia coli isolated from three water sites was investigated to determine the degree of sequence variation in these isolates and to determine whether the polymorphisms in the 16s rRNA genes could be used for the construction of an evolutionary tree. A study was performed to evaluate E.coli species identification obtained by partial 16s rRNA sequencing by the MicroSeq 500 system with an expanded database. A high degree of variation was found between E.coli-EG2 and the other two isolates whilst E.coli-EG1 and E.coli-EG3 showed no distinct polymorphism. Differences within sequences included both polymorphic positions and sequence length of the partially sequenced 16s rRNA genes was done. The phylogenetic tree constructed revealed 97% sequence homology between E.coli-EG1 and E.coli-EG3 to constitute a cluster and 93% homology between these two isolates and E.coli-EG2 that is included in a separate cluster. Two types of polymorphic fragments (null alleles and length mutations) from predicted restriction pattern were observed. The generation of all that variability was attributed to both mutation and horizontal gene transfer (HGT) phenomena accomplished in their original ecological niches.