Cyanide degradation by Bacillus pumilus C1 : cellular and molecular characterization

A cyanide-degrading, Gram-positive, aerobic, endospore-forming bacterium was isolated from a cyanide wastewater dam by an enrichment technique and was identified as a strain of Bacillus pumilus. The bacterium was routinely cultured in Oxoid nutrient broth and rapidly degraded 100 mg/1 of free cyanide in the absence of added inorganic and organic substances. The ability to degrade cyanide was linked to the growth phase and was not exhibited before late-exponential/ early-stationary phase. Cyanide-degrading activity could not be induced in early exponential phase by the addition of cyanide or acetonitrile to 20 mg/1. Production of the cyanide-degrading activity required at least 0.01 mg Mn2+ /1 in the growth medium (lower concentrations prevented the development of strong cyanide-degrading activity and also resulted in poor growth of the organism). No induction of cyanide-degrading activity occurred when Mn2+ ions were added to late-exponential-phase cells (or a cell-free extract from these cells) which had been grown with a low endogenous concentration of Mn2+. However, Mn2+ ions could be added to cultures growing in low-Mn2+ broth as late as the mid-exponential phase of growth with no apparent reduction of the cyanidedegrading activity exhibited in stationary phase. Culturing the organism in Difeo nutrient broth resulted in poor growth and very low levels of cyanide-degrading activity; addition of Mn2+ to this medium did not significantly increase the levels of activity. Production of the cyanide-degrading activity required de novo transcription and translation. Cyanide-degrading activity was located intracellularly and cell-free extracts rapidly degraded cyanide (0.27 ± 0.08 μmole cyanide/min/mg protein at 30 °C in pH 7.4 phosphate buffer). Eight strains of cyanide-utilizing fluorescent pseudomonads were also isolated from activated sewage sludge by an enrichment technique and tentatively identified as strains of P. fluorescens and P. putida. These isolates could not degrade cyanide rapidly.

Grantor dc:publisher.institution

Department of Molecular and Cell Biology

Year dc:date.issued

1993

Author dc:creator

• Meyers, Paul Robert

Advisors dc:contributor.advisor

• Woods, David R
• Rawlings , Douglas E

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/21775

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/21775