Affiliation:
1. Departments of Chemical Engineering and Molecular & Cell Biology, University of Connecticut, 191 Auditorium Rd., Storrs, Connecticut 06269-3222
2. Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Center for Biosystems Research, UMBI, College Park, Maryland 20742
Abstract
ABSTRACT
The cross-species bacterial communication signal autoinducer 2 (AI-2), produced by the purified enzymes Pfs (nucleosidase) and LuxS (terminal synthase) from
S-
adenosylhomocysteine, directly increased
Escherichia coli
biofilm mass 30-fold. Continuous-flow cells coupled with confocal microscopy corroborated these results by showing the addition of AI-2 significantly increased both biofilm mass and thickness and reduced the interstitial space between microcolonies. As expected, the addition of AI-2 to cells which lack the ability to transport AI-2 (
lsr
null mutant) failed to stimulate biofilm formation. Since the addition of AI-2 increased cell motility through enhanced transcription of five motility genes, we propose that AI-2 stimulates biofilm formation and alters its architecture by stimulating flagellar motion and motility. It was also found that the uncharacterized protein B3022 regulates this AI-2-mediated motility and biofilm phenotype through the two-component motility regulatory system QseBC. Deletion of b3022 abolished motility, which was restored by expressing b3022 in
trans
. Deletion of b3022 also decreased biofilm formation significantly, relative to the wild-type strain in three media (46 to 74%) in 96-well plates, as well as decreased biomass (8-fold) and substratum coverage (19-fold) in continuous-flow cells with minimal medium (growth rate not altered and biofilm restored by expressing b3022 in
trans
). Deleting b3022 changed the wild-type biofilm architecture from a thick (54-μm) complex structure to one that contained only a few microcolonies. B3022 positively regulates expression of
qseBC
,
flhD
,
fliA
, and
motA
, since deleting b3022 decreased their transcription by 61-, 25-, 2.4-, and 18-fold, respectively. Transcriptome analysis also revealed that B3022 induces
crl
(26-fold) and
flhCD
(8- to 27-fold). Adding AI-2 (6.4 μM) increased biofilm formation of wild-type K-12 MG1655 but not that of the isogenic b3022,
qseBC
,
fliA
, and
motA
mutants. Adding AI-2 also increased
motA
transcription for the wild-type strain but did not stimulate
motA
transcription for the b3022 and
qseB
mutants. Together, these results indicate AI-2 induces biofilm formation in
E. coli
through B3022, which then regulates QseBC and motility; hence, b3022 has been renamed the motility quorum-sensing regulator gene (the
mqsR
gene).
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
463 articles.
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