The Bacterial Chromosomal Sequence and Related Issues

There has been a rapid increasing in the number of bacterial genomes that are completely sequenced recently. However, nucleotide arrangement in bacterial chromosome is still not clear, though it is known that the chromosomal strand is symmetric as a whole but asymmetric locally. The unequal distribution of adenine and thymine as well as cytosine and guanine in the local genomic sequences has been suggested to be associated with transcription and replication. In the bacterial chromosome, distribution of nucleotides in the leading and lagging strands, which interact with the structurally asymmetric DNA polymerase during replication process, has also been reported to be biased. Recent studies on changing the nucleotide sequence of bacterial chromosomes have revealed the importance of nucleotide arrangement in chromosome, which exerts influences on success of the chromosome engineering experiments. This review highlights common properties of bacterial chromosomal sequences with related issues involved in the nucleotide arrangement in chromosome, emphasizing that arrangement of nucleotides in chromosome regarding local strand asymmetry and chromosomal strand symmetry needs to be made clear so as to help in experimental design for effectiveness in changing chromosomal sequences or creating artificial chromosomes.