A cobalt-resistant wall-less mutant (slime) of Neurospora crassa was obtained by repeated sub-culturing of the sensitive wall-less mutant (W-sl) on agar medium containing toxic concentrations of cobalt. Resistance was stable on culturing Cor-sl on cobalt-free medium up to 15 weekly subcultures. Cor-sl is 10-fold more resistant to cobalt when compared to W-sl. It is also cross-resistant to Cu (10-fold) and Ni (3-fold). Cobalt accumulated by Cor-sl during growth and in short-term uptake experiments was lower when compared to W-sl. Cells previously loaded with cobalt was released into medium in both mutants, while in case of Cor-sl most of cobalt taken up (> 80%), was released back into the medium when compared to W-sl. Metabolic inhibitor (Sodium azide) and magnesium ions inhibited cobalt uptake in both the mutants. Fractionation of cell-free extracts showed that most of the cobalt (70%) taken up by Cor-sl was bound to an inducible protein fraction which bound to DEAE-Cellulose, while in W-sl only 20% of cobalt was associated with this fraction. Subcellular localization of cobalt in W-sl indicated most of it to be cytoplasmic (70%) while nuclei and mitochondria had 10% and 5% respectively. In case of Cor-sl, mitochondrial cobalt accounted for only 2% while no significant differences were noted for other fractions. Our data implicate both transport block and intracellular sequestration of cobalt to play a major role in resistance.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
Ashida J. 1965 Adaptation of fungi to metal toxicants. Ann Rev Phytopathol 3, 153–174.
Gadd GM. 1993 Interactions of fungi with toxic metals. New Phytol 124, 25–60.
Healy HB, Cheng S, McElroy WD. 1955 Metal toxicity and iron deficiency effects on enzymes in Neurospora crassa. Arch Biochem Biophys 54, 206–214.
Kobayashi M and Shimizu S. 1999 Cobalt proteins. Eur J Biochem 261, 1–9.
Lowry OH, Rosenbrough NJ, Farr AL, Randall RJ. 1951 Protein measurement with the folin phenol reagent. J Biol Chem 193, 265–275.
Maruthi Mohan P & Sivarama Sastry K. 1983 Interrelationships in trace element metabolism in metal toxicities in three nickelresistant strains of Neurospora crassa. Biochem J 212, 205–210.
Maruthi Mohan P, Pratap Rudra MP & Sivarama Sastry K. 1984 Nickel transport in nickel-resistant strains of Neurospora crassa. Curr Microbiol 10, 125–128.
Mehra RK & Winge DR. 1991 Metal ion resistance in fungi molecular mechanisms and their regulatory expression. J Cell Biochem 45, 1–11.
RamaRao VSKV, Wilson CH, & Maruthi Mohan P. 1997 Zinc-resistance in Neurospora crassa. Biometals 10, 147–156.
Sajani LS & Maruthi Mohan P. 1997 Characterization of a cobalt-resistant mutant of Neurospora with transport block. BioMetals 10, 175–183.
Sajani LS & Maruthi Mohan P. 1998 Cobalt resistance in Neurospora crassa: Overproduction of a cobaltoprotein in resistant strain. BioMetals 11, 33–40.
Subramanyam C, Venkateswerlu G, Rao SLN. 1983 Cell wall composition of N. crassa under conditions of copper toxicity. Appl Environ Microbiol 46, 585–590.
Venkateswerlu G & Sivarama Sastry K. 1970 The mechanism of uptake of cobalt ions by Neurospora crassa. Biochem J 118, 497–503.
Venkateswerlu G & Sivarama Sastry K. 1973 Interrelationships in trace element metabolism in metal toxicities in a cobalt-resistant strain of Neurospora crassa. Biochem J 132, 673–677.
Venkateswerlu G & Sivarama Sastry K. 1979 Cobalt transport in a cobalt-resistant strain of Neurospora crassa. J Biosci 1, 433–438.
Vogel J. 1956 A convenient growth medium for Neurospora (medium N). Microb Genet Bull 13, 42–43.
About this article
Cite this article
Rajyalaxmi, R., Latha, J.N.L., Rashmi, K. et al. Cobalt-resistance in wall-less mutant (fz; sg; os-1) of Neurospora crassa . Biometals 16, 529–537 (2003). https://doi.org/10.1023/A:1023456118855
- cobalt resistance
- metal transport
- Neurospora crassa
- wall-less mutant