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Biotechnology and Applied Biochemistry (2003) 37, (103–107) (Printed in Great Britain)

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Comparison of cellular stress levels and green-fluorescent-protein expression in several Escherichia coli strains

Jeong Hyun Seo, Dong Gyun Kang and Hyung Joon Cha¹

Department of Chemical Engineering & Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790-784, South Korea

Key words: BL21, HB101, JM105, stress probe, stress response, TOP10.

Abbreviations used: GFP, green fluorescent protein; IPTG, isopropyl b-D-thiogalactoside; SFI, specific fluorescence intensity; SDS/GPAGE, SDS/gelatin PAGE.

¹To whom correspondence should be addressed (e-mail hjcha@postech.ac.kr).

Constructs comprising stress-gene promoter elements from rpoH (Sigma 32), clpB or dnaK linked to a green-fluorescent-protein (GFP) expression vector were previously used as non-invasive 'stress probes' in Escherichia coli. We compared cellular stress responses in four E. coli strains: production hosts JM105 and BL21, and cloning hosts HB101 and TOP10. When GFP was also used as a model for foreign protein production, we generally observed that the level of expression was inversely proportional to the level of cellular stress. JM105 showed the highest cellular stress level and very low GFP expression, while BL21 exhibited the lowest cellular stress level and the highest GFP expression, in both normal and heat-shock stress environments.

Received 16 May 2002/14 October 2002; accepted 16 October 2002

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