Abstract—Cadmium is a natural heavy-metal element. It is highly toxic and a vital industrial pollutant to the environment. In order to survive in heavy-metal polluted environments, some bacteria can withstand high concentrations of heavy metals in environment due to their specific mechanisms, including the transport of heavy metal ions out of the cell. Three kinds of membrane-bound-proteins are known to participate in this transport. The objective of this study was to determine the cadmium-resistant properties and possible mechanism among strains of Cupriavidus metallidurans (= Ralstonia eutropha), C. taiwanensis (=R. taiwanensis) and Ralstonia solanacearum isolated from soil and plants in Taiwan. Strains tested include six strains, rcd 6, 8, 19 (C. metallidurans) and rcd 12, 14, 21 (C. taiwanensis), from cadmium-polluted soil, seventeen strains, nod 1 to nod 5 and nod s1 to s12 (C. taiwanensis) from root nodules of two Mimosa species (M. pudica and M. diplotricha), and ten strains of R. solanacearum isolated from different diseased plants. Sequence analysis of 16S-23S rDNA ITS and nifH gene regions were used to confirm the taxonomic classification of these bacteria. However, the 624-bp PCR product of nifH gene was only amplified from strains nod 1 to nod 3 and nod s1 to s12, but not from other tested strains of Cupriavidus and Ralstonia spp. These tested strains could tolerate cadmium within the range from 0.67 to 6.70 mM. The gene, czcC, thought to encode the outer membrane factor (OMF) of czc efflux system, was found in fifteen tested strains (rcd 6, 8, 12, 14, 19, 21; nod s1 to s6, s9, s11; PSS161) by PCR. Especially, strains rcd 12, 14, and 21 which could tolerate higher cadmium concentration (6.70 mM) harbored the entire czc operon. In addition, the PCR products revealed that cadmium-tolerant strains contained at least a portion of the czc operon and efflux mechanism was confirmed by cadmium uptake test. The results here indicated that cadmium resistant capability in Cupriavidus spp. and R. solanacearum was related to the presence of czcC or czc operon.
Keywords—cadmium-resistant genes (czc operon), Cupriavidus spp., efflux system, Ralstonia solanacearum.
Click here to Download Full Paper
AD Publications is a rapidly growing academic publisher in the fields of Engineering, Medical-Health, Environmental Science and Agriculture Research. AD Publications is a registered organization broad-based open access and publishes most exciting researches with respect to the subjects of our journals. The Journals is being indexed and abstracted by all major global current awareness and alerting services.
The organization aims at undertaking, co- coordinating and promoting research and development. It provides professional and academic guidance in the field of basic education, Higher Education as well in the Technical Education. Our Aims is to Promote and support, High Quality basic, Scientific Research and development in fields of Engineering, Medical-Health, Environmental Science and Agriculture Research and to Generate Public awareness, provide advice to scholar’s researchers and communicate research outcomes.
Some Important Links About Research Journal
International Journal
Agriculture Journal
Medical Journal
Environmental Journal
Engineering Journal