Nickel is an essential element for growth of many microorganisms, as this element is a component of enzymes involved in ureolysis, H2 metabolism, methane production and carbon monoxide utilization. Among the bacteria that utilize nickel for one of these processes, many are bacteria that contain human pathogenic representatives within the genus. Nickel metabolism in general is also of health concern due to its toxic effects on humans. Nevertheless, our knowledge of nickel metabolism is poor. For example, no intracellular Ni-metabolism steps have been identified, even though it is likely that sequential enzymatic nickel-metabolizing processes occur. This proposal is aimed at elucidating the routes of nickel binding, internalization, metabolism, and incorporation into a bacterial enzyme (hydrogenase) in the bacterium Bradyrhizobium japonicum.
The specific aims are to: 1. Purify and characterize a putative nickel storage protein; 2. Determine the number and nature of extracellular and intracellular nickel binding/metabolizing proteins; 3. Determine if nickel can transcriptionally regulate the synthesis of a nickel-containing enzyme; 4. Isolate and characterize mutants in specific nickel-metabolism genes; 5. Isolate genes involved in nickel metabolism and nickel storage to determine their organization, and determine the occurence of these genes in other nickel-utilizing bacteria. The approach included bacterial physiology and biochemistry to determine the pathways of nickel sequestering, storage, processing and eventual insertion into the nickel-containing metalloenzyme hydrogenase. Mutants in nickel metabolism will be isolated to aid in identifying Ni-metabolism enzymes, and molecular genetic techniques will be used to isolate the genes involved. The long-term goal is to help in understanding biochemically and genetically, the number, mature, function, and ubiquity of the components (proteins, genes, other factors) involved in bacterial nickel metabolism.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM040079-04
Application #
3297395
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Project Start
1988-04-01
Project End
1992-09-30
Budget Start
1991-04-01
Budget End
1992-09-30
Support Year
4
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Type
Schools of Arts and Sciences
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Ferber, D M; Maier, R J (1993) Hydrogen-ubiquinone oxidoreductase activity by the Bradyrhizobium japonicum membrane-bound hydrogenase. FEMS Microbiol Lett 110:257-64
Fu, C; Maier, R J (1993) A genetic region downstream of the hydrogenase structural genes of Bradyrhizobium japonicum that is required for hydrogenase processing. J Bacteriol 175:295-8
Kim, H; Gabel, C; Maier, R J (1993) Expression of hydrogenase in Hupc strains of Bradyrhizobium japonicum. Arch Microbiol 160:43-50
Fu, C; Maier, R J (1993) Rapid and efficient selection of recombinant site-directed mutants of Bradyrhizobium japonicum by colony hybridization. FEMS Microbiol Lett 109:33-8
Fu, C; Maier, R J (1992) Nickel-dependent reconstitution of hydrogenase apoprotein in Bradyrhizobium japonicum Hupc mutants and direct evidence for a nickel metabolism locus involved in nickel incorporation into the enzyme. Arch Microbiol 157:493-8
Ferber, D M; Maier, R J (1992) Incorporation of a bacterial membrane-bound hydrogenase into proteoliposomes. Anal Biochem 203:235-44
Fu, C L; Maier, R J (1991) Competitive inhibition of an energy-dependent nickel transport system by divalent cations in Bradyrhizobium japonicum JH. Appl Environ Microbiol 57:3511-6
Moshiri, F; Chawla, A; Maier, R J (1991) Cloning, characterization, and expression in Escherichia coli of the genes encoding the cytochrome d oxidase complex from Azotobacter vinelandii. J Bacteriol 173:6230-41
Fu, C L; Maier, R J (1991) Identification of a locus within the hydrogenase gene cluster involved in intracellular nickel metabolism in Bradyrhizobium japonicum. Appl Environ Microbiol 57:3502-10
Moshiri, F; Smith, E G; Taormino, J P et al. (1991) Transcriptional regulation of cytochrome d in nitrogen-fixing Azotobacter vinelandii. Evidence that up-regulation during N2 fixation is independent of nifA but dependent on ntrA. J Biol Chem 266:23169-74

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