Darwin and microbial evolution

In the 200th year of Charles Darwin’s birth anniversary and 150th year of the publication of the ‘Origin of Species’, biologists are trying to re-evaluate the concept of the evolution as propounded by Darwin in the light of the knowledge gathered through recent developments in genomics and proteomics. Since no technique existed for the isolation of bacteria and the tremendous diversity of the microbial world was still largely unknown, at the time Darwin wrote his masterpiece, concept of microbial evolution was not widely discussed. This was further compounded by the lack of a theoretical basis of the concept of species in prokaryotes as microbial lineages show substantial variation in population structure, ranging from essentially clonal to nearly sexual. Comparative genomic studies have revealed that prokaryotic genetic material are under continuous selective pressure that have profoundly influenced its organization indicating that the gene pool available in the microbial world is far larger than previously thought. As per established knowledge of microbial genetics, local DNA sequence changes, segment-wise rearrangement of genomic DNA sequences by recombinational reshuffling and horizontal gene transfer are the evolutionary processes shaping the genome of the prokaryotes. Modern knowledge of the molecular biology of the genes and their expression has provided a strong input in understanding the genome-wide map of selection, linking gene variation to phenotype and ecology.