Affiliation:
1. Department of Chemical Engineering, University of California, Berkeley, California 94720-1462
Abstract
ABSTRACT
The thiosulfate reductase gene (
phsABC
) from
Salmonella enterica
serovar Typhimurium was expressed in
Escherichia coli
to overproduce hydrogen sulfide from thiosulfate for heavy metal removal (or precipitation). A 5.1-kb DNA fragment containing
phsABC
was inserted into the pMB1-based, high-copy, isopropyl-β-
d
-thiogalactopyranoside-inducible expression vector pTrc99A and the RK2-based, medium-copy,
m
-toluate-inducible expression vector pJB866, resulting in plasmids pSB74 and pSB77. A 3.7-kb DNA fragment, excluding putative promoter and regulatory regions, was inserted into the same vectors, making plasmids pSB103 and pSB107.
E. coli
DH5α strains harboring the
phsABC
constructs showed higher thiosulfate reductase activity and produced significantly more sulfide than the control strains under both aerobic and anaerobic conditions. Among the four
phsABC
constructs,
E. coli
DH5α (pSB74) produced thiosulfate reductase at the highest level and removed the most cadmium from solution under anaerobic conditions: 98% of all concentrations up to 150 μM and 91% of 200 μM. In contrast, a negative control did not produce any measurable sulfide and removed very little cadmium from solution. Energy-dispersive X-ray spectroscopy revealed that the metal removed from solution precipitated as a complex of cadmium and sulfur, most likely cadmium sulfide.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
51 articles.
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