A beta subtype methylase that recognizes the double-stranded sequence 5'-GANTC-3' and methylates A-2 on both strands (Probable) (PubMed:12654995). Overexpression leads to many branched and bloated cells, two to three times the size of wild-type cells, and cells that have 1-3 times the normal amount of DNA. Contributes to the accurate cell-cycle control of DNA replication and cellular morphology. Can fully replace its ortholog in C.crescentus (PubMed:9294447). a 2'-deoxyadenosine in DNA + S-adenosyl-L-methionine = an N(6)-methyl-2'-deoxyadenosine in DNA + H(+) + S-adenosyl-L-homocysteine Essential, it cannot be disrupted. Belongs to the N(4)/N(6)-methyltransferase family.