scholarly journals Inactivation of ompX Causes Increased Interactions of Type 1 Fimbriated Escherichia coli with Abiotic Surfaces

2004 ◽  
Vol 186 (1) ◽  
pp. 226-234 ◽  
Author(s):  
Karen Otto ◽  
Malte Hermansson
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Cell Surface ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Phenotypic Characterization ◽  
Phenotypic Changes ◽  
Mutant Strains ◽  
Surface Contact

ABSTRACT During the initial steps of biofilm formation, bacteria have to adapt to a major change in their environment. The adhesion-induced phenotypic changes in a type 1 fimbriated Escherichia coli strain included reductions in the levels of several outer membrane proteins, one of which was identified as OmpX. Here, the phenotypes of mutant strains that differ at the ompX locus were studied with regard to adhesion, cell surface properties, and resistance to stress and antimicrobial compounds. The kinetics of adhesion were measured online by an extended quartz crystal microbalance technique for wild-type and mutant strains with a fimbriated or nonfimbriated background. Deletion of ompX led to significantly increased cell-surface contact in fimbriated strains but to decreased cell-surface contact in a nonfimbriated strain. Phenotypic characterization of the ompX mutant demonstrated that ompX interferes with proper regulation of cell surface structures that play a key role in mediating firm contact of the cell with a surface (i.e., type 1 fimbriae, flagellae, and exopolysaccharides). These phenotypic changes were accompanied by increased tolerance to several antibiotic compounds and sodium dodecyl sulfate. Based on these results, we propose that changes in the composition of outer membrane proteins during fimbria-mediated adhesion may be part of a coordinated adaptive response to the attached mode of growth.

scholarly journals Adhesion of Type 1-Fimbriated Escherichia coli to Abiotic Surfaces Leads to Altered Composition of Outer Membrane Proteins

2001 ◽  
Vol 183 (8) ◽  
pp. 2445-2453 ◽  
Author(s):  
Karen Otto ◽  
Joakim Norbeck ◽  
Thomas Larsson ◽  
Karl-Anders Karlsson ◽  
Malte Hermansson
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Cell Envelope ◽  
Outer Membrane Proteins ◽  
Polyacrylamide Gel Electrophoresis ◽  
Surface Characteristics ◽  
Abiotic Surfaces

ABSTRACT Phenotypic differences between planktonic bacteria and those attached to abiotic surfaces exist, but the mechanisms involved in the adhesion response of bacteria are not well understood. By the use of two-dimensional (2D) polyacrylamide gel electrophoresis, we have demonstrated that attachment of Escherichia coli to abiotic surfaces leads to alteration in the composition of outer membrane proteins. A major decrease in the abundance of resolved proteins was observed during adhesion of type 1-fimbriated E. colistrains, which was at least partly caused by proteolysis. Moreover, a study of fimbriated and nonfimbriated mutants revealed that these changes were due mainly to type 1 fimbria-mediated surface contact and that only a few changes occurred in the outer membranes of nonfimbriated mutant strains. Protein synthesis and proteolytic degradation were involved to different extents in adhesion of fimbriated and nonfimbriated cells. While protein synthesis appeared to affect adhesion of only the nonfimbriated strain, proteolytic activity mostly seemed to contribute to adhesion of the fimbriated strain. Using matrix-assisted laser desorption ionization–time of flight mass spectrometry, six of the proteins resolved by 2D analysis were identified as BtuB, EF-Tu, OmpA, OmpX, Slp, and TolC. While the first two proteins were unaffected by adhesion, the levels of the last four were moderately to strongly reduced. Based on the present results, it may be suggested that physical interactions between type 1 fimbriae and the surface are part of a surface-sensing mechanism in which protein turnover may contribute to the observed change in composition of outer membrane proteins. This change alters the surface characteristics of the cell envelope and may thus influence adhesion.

scholarly journals Regulated Delayed Expression of rfaH in an Attenuated Salmonellaenterica Serovar Typhimurium Vaccine Enhances Immunogenicity of Outer Membrane Proteins and a Heterologous Antigen

2009 ◽  
Vol 77 (12) ◽  
pp. 5572-5582 ◽  
Author(s):  
Qingke Kong ◽  
Qing Liu ◽  
Kenneth L. Roland ◽  
Roy Curtiss
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Lethal Dose ◽  
Enteric Bacteria ◽  
Lymphoid Tissues ◽  
Heterologous Antigen ◽  
O Antigen ◽  
Mutant Strains ◽  
Serovar Typhimurium

ABSTRACT RfaH is a transcriptional antiterminator that reduces the polarity of long operons encoding secreted and surface-associated cell components of Salmonella enterica serovar Typhimurium, including O antigen and lipopolysaccharide core sugars. A ΔrfaH mutant strain is attenuated in mice (50% lethal dose [LD50], >108 CFU). To examine the potential for using rfaH in conjunction with other attenuating mutations, we designed a series of strains in which we replaced the native rfaH promoter with the tightly regulated arabinose-dependent araC PBAD promoter so that rfaH expression was dependent on exogenously supplied arabinose provided during in vitro growth. Following colonization of host lymphoid tissues, where arabinose was not available, the PBAD promoter was no longer active and rfaH was not expressed. In the absence of RfaH, O antigen and core sugars were not synthesized. We constructed three mutant strains that expressed different levels of RfaH by altering the ribosome-binding sequence and start codon. One mutation, ΔPrfaH178, was introduced into the attenuated vaccine strain χ9241 (ΔpabA ΔpabB ΔasdA) expressing the pneumococcal surface protein PspA from an Asd+ balanced-lethal plasmid. Mice immunized with this strain and boosted 4 weeks later induced higher levels of serum immunoglobulin G specific for PspA and for outer membrane proteins from other enteric bacteria than either an isogenic ΔrfaH derivative or the isogenic RfaH+ parent. Eight weeks after primary oral immunization, mice were challenged with 200 LD50 of virulent S treptococcus pneumoniae WU2. Immunization with ΔPrfaH178 mutant strains led to increased levels of protection compared to that of the parent χ9241 and of a ΔrfaH derivative of χ9241.

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