Microsatellite polymorphism across the M. tuberculosis and M. bovis genomes: implications on genome evolution and plasticity.
BACKGROUND
Microsatellites are the tandem repeats of nucleotide motifs of size 1-6 bp observed in all known genomes. These repeats show length polymorphism characterized by either insertion or deletion (indels) of the repeat units, which in and around the coding regions affect transcription and translation of genes.


RESULTS
Systematic comparison of all the equivalent microsatellites in the coding regions of the three mycobacterial genomes, viz. Mycobacterium tuberculosis H37Rv, Mycobacterium tuberculosis CDC1551 and Mycobacterium bovis, revealed for the first time the presence of several polymorphic microsatellites. The coding regions affected by frame-shifts owing to microsatellite indels have undergone changes indicative of gene fission/fusion, premature termination and length variation. Interestingly, the genes affected by frame-shift mutations code for membrane proteins, transporters, PPE, PE_PGRS, cell-wall synthesis proteins and hypothetical proteins.


CONCLUSIONS
This study has revealed the role of microsatellite indel mutations in imparting novel functions and a certain degree of plasticity to the mycobacterial genomes. There seems to be some correlation between microsatellite polymorphism and the variations in virulence, host-pathogen interactions mediated by surface antigen variations, and adaptation of the pathogens. Several of the polymorphic microsatellites reported in this study can be tested for their polymorphic nature by screening clinical isolates and various mycobacterial strains, for establishing correlations between microsatellite polymorphism and the phenotypic variations among these pathogens.
Sreenu
Vattipally B
VB
Laboratory of Computational Biology, Centre for DNA Fingerprinting and Diagnostics, ECIL Road, Nacharam, Hyderabad-76, A,P., India. sreenu@cdfd.org.in
Kumar
Pankaj
P
Nagaraju
Javaregowda
J
Nagarajaram
Hampapathalu A
HA
D001426:Bacterial Proteins / Q000235:genetics; D019143:Evolution, Molecular; D016368:Frameshift Mutation; D016680:Genome, Bacterial; D018895:Microsatellite Repeats; D009163:Mycobacterium bovis / Q000235:genetics*; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D016366:Open Reading Frames; D011110:Polymorphism, Genetic
D001426:Bacterial Proteins