Each bacterial gene is denoted by a mnemonic of three lower case letters which indicate the pathway or process in which the gene-product is involved, followed by a capital letter signifying the actual gene. In some cases, the gene letter may be followed by an allele number. All letters and numbers are underlined or italicised.  For example, leuA is one of the genes of the leucine biosynthetic pathway, and leuA273 is a particular allele of this gene.
Where the actual protein coded by the gene is known then it may become part of the basis of the mnemonic, thus:
*rpoA encodes the α-subunit of RNA polymerase
*rpoB encodes the β-subunit of RNA polymerase
*polA encodes DNA polymerase I
*polC encodes DNA polymerase III
*rpsL encodes ribosomal protein, small S12
Some gene designations refer to a known general function:
*dna is involved in DNA replication