ActivityAffected in Melanization and Laccase Isolation of Azospirillum lipoferum 4T Tn5

werealso colorless.TheTn5localization onthe chromosomeoronthe cryptic 300-MDaplasmidofA. lipoferum 4Twasprovenbyhybridization for all class 1 mutants orfor mostclass 2 mutants, respectively.Laccases can oxidize, demethylate, polymerize, or depoly-merize phenolic compounds. Laccases have been associatedwith lignification in plants (3) and with different biologicalmechanismsin fungi, such as phytopathogenicity or resistanceto environmental or microbial stress (4). Thelaccases oxidizep- and o-diphenols, whereas tyrosinases oxidize o-diphenolsandmonophenols. Laccasesandtyrosinases arebothclassifiedin the polyphenoloxidase (PPO) group. PPOsare widespreadin nature; laccases are present primarily in various fungi andhigherplants, while the occurrenceoftyrosinases in organismsis almost universal (20). In bacteria, tyrosinase is the bestknownPPO-typeenzymeandwasfirst described in Streptomy-