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Differential regulation of six heavy metal efflux systems in the response of Myxococcus xanthus to copper.

ABSTRACT: Myxococcus xanthus has to cope with changes in its environment during growth and development. Among these factors, the concentration of copper is crucial due to the essential toxic effect of this metal, which forces the cells to maintain a tight homeostasis. The M. xanthus copper response is more complex than that in other bacteria, which is reflected by the different copper sensitivities of growing and developing cells. In the present study, the participation in copper homeostasis of six heavy metal efflux systems encoded in the M. xanthus genome has been examined. Three of these pumps exhibit the signature sequences in transmembrane domain 4 of the Cus systems (Cus1, Cus2, and Cus3), while the other three exhibit the motifs of the Czc systems (Czc1, Czc2, and Czc3). The Cus2 and Cus3 systems are inducible by copper and monovalent metals, functioning as the main copper efflux pumps, while the Cus1 system is implicated in Zn(2+) homeostasis. The Czc systems are also differentially regulated either by divalent metals but not by copper (Czc1), by copper and divalent metals (Czc2), or by starvation (Czc3). The differential regulation of these six efflux systems ensures the proper completion of the M. xanthus life cycle in an environment with fluctuating concentrations of copper and other metals.

SUBMITTER: Moraleda-Munoz A

PROVIDER: S-EPMC2937488 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Differential regulation of six heavy metal efflux systems in the response of Myxococcus xanthus to copper.

Moraleda-Muñoz Aurelio A Pérez Juana J Extremera Antonio Luis AL Muñoz-Dorado José J

Applied and environmental microbiology 20100618 18

Myxococcus xanthus has to cope with changes in its environment during growth and development. Among these factors, the concentration of copper is crucial due to the essential toxic effect of this metal, which forces the cells to maintain a tight homeostasis. The M. xanthus copper response is more complex than that in other bacteria, which is reflected by the different copper sensitivities of growing and developing cells. In the present study, the participation in copper homeostasis of six heavy ...[more]

PMID: 20562277

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Project description:Myxococcus xanthus is a soil myxobacterium that exhibits a complex lifecycle with two multicellular stages: cooperative predation and development. During predation, myxobacterial cells produce a wide variety of secondary metabolites and hydrolytic enzymes to kill and consume the prey. It is known that eukaryotic predators, such as ameba and macrophages, introduce copper and other metals into the phagosomes to kill their prey by oxidative stress. However, the role of metals in bacterial predation has not yet been established. In this work, we have addressed the role of copper during predation of M. xanthus on Sinorhizobium meliloti. The use of biosensors, variable pressure scanning electron microscopy, high-resolution scanning transmission electron microscopy, and energy dispersive X ray analysis has revealed that copper accumulates in the region where predator and prey collide. This accumulation of metal up-regulates the expression of several mechanisms involved in copper detoxification in the predator (the P1 B-ATPase CopA, the multicopper oxidase CuoA and the tripartite pump Cus2), and the production by the prey of copper-inducible melanin, which is a polymer with the ability to protect cells from oxidative stress. We have identified two genes in S. meliloti (encoding a tyrosinase and a multicopper oxidase) that participate in the biosynthesis of melanin. Analysis of prey survivability in the co-culture of M. xanthus and a mutant of S. meliloti in which the two genes involved in melanin biosynthesis have been deleted has revealed that this mutant is more sensitive to predation than the wild-type strain. These results indicate that copper plays a role in bacterial predation and that melanin is used by the prey to defend itself from the predator. Taking into consideration that S. meliloti is a nitrogen-fixing bacterium in symbiosis with legumes that coexists in soils with M. xanthus and that copper is a common metal found in this habitat as a consequence of several human activities, these results provide clear evidence that the accumulation of this metal in the soil may influence the microbial ecosystems by affecting bacterial predatory activities.

Dataset Information

Differential regulation of six heavy metal efflux systems in the response of Myxococcus xanthus to copper.

Publications

Differential regulation of six heavy metal efflux systems in the response of Myxococcus xanthus to copper.

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