Abstract:
:Escherichia coli has been used as a platform host for studying the production of free fatty acids (FFA) and other energy-dense compounds useful in biofuel applications. Most of the FFA produced by E. coli are found extracellularly. This finding suggests that a mechanism for transport across the cell envelope exists, yet knowledge of proteins that may be responsible for export remains incomplete. Production of FFA has been shown to cause cell lysis, induce stress responses, and impair basic physiological processes. These phenotypes could potentially be diminished if efflux rates were increased. Here, a total of 15 genes and operons were deleted and screened for their impact on cell viability and titer in FFA-producing E. coli. Deletions of acrAB and rob and, to a lower degree of statistical confidence, emrAB, mdtEF, and mdtABCD reduced multiple measures of viability, while deletion of tolC nearly abolished FFA production. An acrAB emrAB deletion strain exhibited greatly reduced FFA titers approaching the tolC deletion phenotype. Expression of efflux pumps on multicopy plasmids did not improve endogenous FFA production in an acrAB(+) strain, but plasmid-based expression of acrAB, mdtEF, and an mdtEF-tolC artificial operon improved the MIC of exogenously added decanoate for an acrAB mutant strain. The findings suggest that AcrAB-TolC is responsible for most of the FFA efflux in E. coli, with residual activity provided by other resistance-nodulation-cell division superfamily-type efflux pumps, including EmrAB-TolC and MdtEF-TolC. While the expression of these proteins on multicopy plasmids did not improve production over the basal level, their identification enables future engineering efforts.
journal_name
J Bacterioljournal_title
Journal of bacteriologyauthors
Lennen RM,Politz MG,Kruziki MA,Pfleger BFdoi
10.1128/JB.01477-12subject
Has Abstractpub_date
2013-01-01 00:00:00pages
135-44issue
1eissn
0021-9193issn
1098-5530pii
JB.01477-12journal_volume
195pub_type
杂志文章abstract::To examine the role of the amino acid residues (between positions 258 and 275 and positions 297 and 298) of the alpha-subunit of RNA polymerase in TyrR-mediated activation of the mtr promoter, we have carried out in vitro transcription experiments using a set of mutant RNA polymerases with a supercoiled mtr template. ...
journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.179.19.6187-6191.1997
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pub_type: 杂志文章
doi:10.1128/JB.181.20.6396-6402.1999
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journal_title:Journal of bacteriology
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pub_type: 杂志文章
doi:10.1128/jb.170.3.1319-1324.1988
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journal_title:Journal of bacteriology
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pub_type: 杂志文章
doi:10.1128/JB.109.2.773-779.1972
更新日期:1972-02-01 00:00:00
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更新日期:1982-08-01 00:00:00
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更新日期:2002-08-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.137.3.1386-1394.1979
更新日期:1979-03-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
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更新日期:1970-02-01 00:00:00
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pub_type: 杂志文章
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pub_type: 杂志文章
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更新日期:1994-06-01 00:00:00