Arsenic and chromium resistance mechanisms in the Micrococcus luteus group |
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| Authors: | Ivan ARROYO-HERRERA Brenda ROM&#;N-PONCE Rafael BUSTAMANTE-BRITO Joseph GUEVARA-LUNA Erika Yanet TAPIA-GARC&#;A Violeta LARIOS-SERRATO Nannan ZHANG Paulina ESTRADA-DE LOS SANTOS En Tao WANG and Mar&#;a Soledad V&#;SQUEZ-MURRIETA |
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| Institution: | 1 Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México 11340(Mexico)
2 Universidad Politécnica del Estado de Morelos, Jiutepec 62550(Mexico)
3 Centro de Ciencias Genómicas, Universidad Autónoma de México, Cuernavaca 62210(Mexico)
4 CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilisation&Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041(China) |
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| Abstract: | High arsenic (As) and chromium (Cr) concentrations are currently receiving attention because of their negative effects on the environment and human health. Microorganisms inhabiting contaminated environments have developed resistance mechanisms against the toxicity of these pollutants. Indeed, members of the bacterial genus Micrococcus have been isolated from different toxic metal-contaminated environments; however, knowledge concerning its resistance mechanisms to As and Cr toxicity remains limited. Micrococcus luteus strains (An24, Mh, NE2TL6, and NE2TTS4) were isolated from the endosphere and soil of two heavy metal-contaminated sites in Mexico to identify differences in the resistance mechanisms by the M. luteus group. The strains were resistant to As (As3+ and As5+), chromate, dichromate, cobalt, copper, nickel, and zinc. Genome analysis indicated that the heavy metal-resistant strains (An24, Mh, NE2TL6, and NE2TTS4) could be assigned to the M. luteus group and had more heavy metal-resistant genes (transporters, chaperones, and enzymes) compared to reference strains of the M. luteus group, M. luteus NCTC 2665T and Micrococcus endophyticus JCM 16951T. The resistant bacteria were able to biotransform As3+ and As5+ through a carbon source-dependent mechanism. The biotransformation of As5+ was potentially carried out in the cytoplasm through a thioredoxin-dependent pathway, which may be coupled with biosorption. A qualitative analysis of organic acids (OAs) identified a change in the OA profile of the metal-resistant strains that was As- or Cr-dependent. Our genomic and phenotypic findings suggest that the four M. luteus group strains evaluated in the current study have developed resistance mechanisms that may enable their survival in contaminated sites. |
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| Keywords: | arsenophore biosorption genome analysis heavy metal-resistant strain immobilization organic acid pollutant |
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