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J. Bacteriol. doi:10.1128/JB.00309-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Differential expression of the three multicopper oxidases from Myxococcus xanthus

Departamento de Microbiología. Instituto de Biotecnología. Facultad de Ciencias. Universidad de Granada. Avda. Fuentenueva s/n. E-18071 Granada. Spain; Instituto de Tecnologia Química e Biológica (ITQB). Universidade Nova de Lisboa. Avda República. 2785-901 Oeiras. Portugal

^* To whom correspondence should be addressed. Email: jdorado{at}ugr.es.

	Abstract

Myxococcus xanthus is a soil bacterium that undergoes a unique life cycle among the prokaryotes upon starvation, which includes the formation of macroscopic structures, the fruiting bodies, and the differentiation of vegetative rods into coccoid myxospores. This peculiarity offers the opportunity to study the copper response in this bacterium in two different stages. In fact, M. xanthus vegetative rods exhibit 15-fold higher resistance against copper than developing cells. However, cells preadapted to this metal reach the same levels of resistance during both stages. Analysis of the M. xanthus genome reveals that many of the genes involved in copper resistance are redundant, three of which encode proteins of the multicopper oxidase family (MCO). Each MCO gene exhibits a different expression profile in response to external copper addition. Promoters of cuoA and cuoB respond to Cu(II) ions during growth and development; however, they showed 10-fold increased copper sensitivity during development. Promoter of cuoC shows copper-independent induction upon starvation, but it is copper up-regulated during growth. Phenotypic analyses of deletion mutants have revealed that CuoB is involved in the primary copper adaptive response; CuoA and CuoC are necessary for the maintenance of the copper tolerance; and CuoC is required for normal development. These roles seem to be carried out through cuprous oxidase activity.