Matthias A Ehrmann

Technische Universität München, München, Bavaria, Germany

Are you Matthias A Ehrmann?

Claim your profile

Publications (65)149.67 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We have performed a transcriptomic in vivo study with Enterococcus faecalis OG1RF in the intestine of living mice to identify novel latent and adaptive fitness determinants within E. faecalis. From 2,658 genes that are present in E. faecalis strain OG1RF, 124 genes were identified as significantly differentially expressed within the intestinal tract of living mice as compared to exponential growth in BHI broth. The groups of significantly up- or down-regulated genes consisted of 94 and 30 genes, respectively, for which 46 and 18 a clear annotation to a functionally described protein was found. These included genes involved in energy metabolism (e.g., dhaK and glpK pathway), transport and binding mechanisms (e.g., phosphoenolpyruvate carbohydrate PTS) as well as fatty acid metabolism (fab genes). The novel putative fitness determinants found in this work may be helpful for future studies of E. faecalis adaptation to the intestinal tract, which is also a prerequisite for infection in a compromised or inflamed host.
    Archives of Microbiology 04/2014; · 1.86 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This study focuses on the impact of actin on adhesion and translocation of Enterococcus (E.) faecalis OG1RF, E. faecalis Symbioflor(®), and E. faecalis V583. Insight into the role of actin aggregation in the mediation of bacterial adhesion and translocation was provided by a two-chamber translocation assay, which employed Ptk6 cells. Determination of translocation rates, cytochalasin D treatment, and laser scanning confocal microscopic observation revealed actin as a predominant brace for enterococci to pass through the epithelial cell layer. As the three enterococci had moderate adhesion ability to actin, actin-binding proteins were isolated and characterized by LC-MS/MS. The isolated proteins were identified as pyruvate formate lyase, enolase, glyceraldehyde-3-phosphate dehydrogenase, and GroEL. All these proteins belong to two major groups of moonlighting proteins, i.e., proteins, which display additional functions other than their described major biochemical catalysis. Both groups of moonlight proteins were determined to be associated with epithelial cell binding.
    Archives of Microbiology 12/2013; · 1.86 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Bacteriophages infection modulates microbial consortia and transduction is one of the most important mechanism involved in the bacterial evolution. However, phage contamination brings food fermentations to a halt causing economic setbacks. The number of phage genome sequences of lactic acid bacteria especially of lactobacilli is still limited. We analysed the genome of a temperate phage active on Lactobacillus sanfranciscensis, the predominant strain in type I sourdough fermentations. Sequencing of the DNA of EV3 phage revealed a genome of 34,834 bp and a G + C content of 36.45%. Of the 43 open reading frames (ORFs) identified, all but eight shared homology with other phages of lactobacilli. A similar genomic organization and mosaic pattern of identities align EV3 with the closely related Lactobacillus vaginalis ATCC 49540 prophage. Four unknown ORFs that had no homologies in the databases or predicted functions were identified. Notably, EV3 encodes a putative dextranase. EV3 is the first L. sanfranciscensis phage that has been completely sequenced so far.
    BMC Research Notes 12/2013; 6(1):514.
  • Jasmin Stadie, Anna Gulitz, Matthias A Ehrmann, Rudi F Vogel
    [Show abstract] [Hide abstract]
    ABSTRACT: Water kefir is a mildly sour and alcoholic drink fermented by a stable microbial multispecies community. With its high sugar content and low amino acid concentration water kefir medium represents a demanding habitat. In this ecological niche only well adapted microorganisms which are fit to the consortium are able to grow and mutually provide essential nutrients. The synergism between main representatives of water kefir yeasts and lactobacilli was studied in a co-culture model system. Co-cultivation of yeasts and lactobacilli in water kefir medium significantly increased cell yield of all interaction partners, delineating the interaction of these water kefir isolates as mutualism. The support of Zygotorulaspora (Z.) florentina was due to the acidification of the medium by the lactobacilli, whereas lactobacilli are improved in growth by the disposal of essential nutrients produced by yeasts. The trophic interaction between Lactobacillus (Lb.) hordei and yeasts is constituted by the release of amino acids and Vitamin B6 from yeasts, whereas Lb. nagelii is supported in growth by their production of amino acids. The interaction of Z. florentina and Lb. nagelii was further examined to reveal that co-cultivation induced the yeast to release arginine, which was essential for Lb. nagelii.
    Food Microbiology 09/2013; 35(2):92-8. · 3.37 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: AIMS: The aim of this study was to analyse the bacterial microbiota of water kefir using culture-independent methods. METHODS AND RESULTS: We compared four water kefirs of different origins using 16S rDNA amplicon sequencing and ARDRA. The microbiota consisted of different proportions of the genera Lactobacillus (Lb.), Leuconostoc (Lc.), Acetobacter (Ac.) and Gluconobacter. Surprisingly, varying but consistently high numbers of sequences representing members of the genus Bifidobacterium (B.) were found in all kefirs. Whereas part of the bifidobacterial sequences could be assigned to B. psychraerophilum, a majority of sequences identical to each other could not be assigned to any known species. A nearly full-length sequence of the latter exhibited a beyond-species similarity (96.4%) with the sequence from the closest relative species B. psychraerophilum. A Bifidobacterium-specific ARDRA analysis reflected the abundance of the novel Bifidobacterium species by revealing its unique MboI restriction profile. Attempts to isolate the bifidobacteria were successful for B. psychraerophilum only. CONCLUSIONS: The complexity of the water kefir microbiota has been underestimated in previously studies. The occurrence of Bifidobacteria as part of the consortium is novel. SIGNIFICANCE AND IMPACT OF STUDY: These data give new insights in the understanding of the complexity of food fermentations and underlines the need for approaches detecting non-cultivable organisms. © 2013 The Authors Journal of Applied Microbiology © 2013 The Society for Applied Microbiology.
    Journal of Applied Microbiology 01/2013; · 2.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Enterococcus (E.) faecalis is found as commensal in healthy humans, in a variety of fermented foods. It can serve as probiotic but also as pathogen causing endocarditis, bacteremia and urinary tract infections. We have employed a proteomic study with E. faecalis strain OG1RF under different growth conditions and in contact to mouse intestinal cells to identify novel latent and adaptive fitness determinants. These relate to changes in catabolic pathways (BudA), protein biosynthesis (AsnS), cellular surface biosynthesis (RmlA) and regulatory mechanisms (OmpR). This knowledge can be used to derive novel evidence-based targets, which can be used to further elucidate gene expression changes enhancing pathogenicity or fitness in a commensal strain and possibly delineate this species into groups of higher and lower risk for applications in a food or a medical context versus improved treatment strategies of the so far hard to cure diseases.
    Archives of Microbiology 12/2012; · 1.86 Impact Factor
  • Simone Freiding, Matthias A Ehrmann, Rudi F Vogel
    [Show abstract] [Hide abstract]
    ABSTRACT: Branched chain aminotransferases (IlvE/BcaT), specific for leucine, isoleucine, and valine initialize the formation of methyl-branched volatiles, which are strongly linked to the typical aroma of cured meat products. Lactobacillus sakei, one of the dominating lactic acid bacteria species for meat fermentations and commonly used as starter lacks this enzyme, whereas the presence of IlvE has been reported for Lactobacillus paracasei, a non-starter lactic acid bacterium occurring in meat products and with probiotic properties, in Staphylococcus carnosus, a catalase positive cocci also used as starter for meat products, and in Enterococcus faecalis belonging to the natural microbiota of meat and that may impact on the aroma of fermented meat products. The genes for branched-chain aminotransferases of these three bacterial species were used to complement the IlvE negative strain L. sakei TMW1.1322. For that purpose, ilvE genes were heterologously expressed in L. sakei TMW1.1322 under the control of the constitutive L. sakei promotor pldhL via replicative plasmids and chromosomal integration. To examine effective expression the constructs were transcriptionally coupled to mCherry, a red fluorescent protein. Aminotransferase activities and formation of volatile compounds were compared. Activities of L. sakei ArcT and AspD purified enzymes were also measured. Conversion of branched chain amino acids to the corresponding α-keto-acids was significantly increased in all transformants expressing the ilvE genes. The activity of IlvE obtained from L. paracasei was highest. Substrate specificities of IlvEs towards leucine, isoleucine and valine were similar. However, enhanced transaminase activities did not increase formation of the respective methyl-branched volatiles by recombinant L. sakei strains. This indicates that presence of ilvE cannot be the only bottleneck in aroma formation from amino acids. Amino acid or peptide uptake into the cell via specific transport systems and the conversion of α-keto acids to the corresponding aldehydes, alcohols and carboxylic acids must be considered as further limiting steps.
    Food Microbiology 04/2012; 29(2):205-14. · 3.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The microbial diversity of water kefir, made from a mixture of water, dried figs, a slice of lemon and sucrose was studied. The microbial consortia residing in the granules of three water kefirs of different origins were analyzed. A collection of 453 bacterial isolates was obtained on different selective/differential media. Bacterial isolates were grouped with randomly amplified polymorphic DNA (RAPD)-PCR analyses. One representative of each RAPD genotype was identified by comparative 16S rDNA gene sequencing. The predominant genus in water kefirs I and II was Lactobacillus, which accounted for 82.1% in water kefir I and 72.1% in water kefir II of the bacterial isolates. The most abundant species in water kefirs I and II were Lactobacillus hordei and Lb. nagelii followed by considerably lower numbers of Lb. casei. Other lactic acid bacteria (LAB) were identified as Leuconostoc mesenteroides and Lc. citreum in all three water kefirs. The most abundant species in water kefir III was Lc. mesenteroides (28%) and Lc. citreum (24.3%). A total of 57 LAB belonging to the species of Lb. casei, Lb. hordei, Lb. nagelii, Lb. hilgardii and Lc. mesenteroides were able to produce exopolysacchrides from sucrose. Non LABs were identified as Acetobacter fabarum and Ac. orientalis. The Acetobacter species were more prevalent in consortium III. Cluster analyses of RAPD-PCR patterns revealed an interspecies diversity among the Lactobacillus and Acetobacter strains. Aditionally, Saccharomyces cerevisiae, Lachancea fermentati, Hanseniaospora valbyensis and Zygotorulaspora florentina were isolated and identified by comparison of partial 26S rDNA sequences and FTIR spectroscopy.
    International journal of food microbiology 12/2011; 151(3):284-8. · 3.01 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Enterococcus faecalis and Enterococcus faecium are human commensals frequently found in fermented foods or used as probiotics, but also recognized as opportunistic pathogens. We investigated 62 Enterococcus strains isolated from clinical, food and environmental origins towards a rationale for safety evaluation of strains in food or probiotic applications. All isolates were characterised with respect to the presence of the virulence determinants fsrB, sprE, gelE, ace, efaAfs/fm, as, esp, cob and the cytolysin operon. In addition RAPD-PCR was used to obtain genomic fingerprints that were clustered and compared to phenotypic profiles generated by MALDI-TOF-MS. The gelatinase phenotype (GelE) and the haemolytic activity (β-haemolysis) were analysed. E. faecium strains contained esp and efaAfm only, and none of them contained any CRISPR elements. The amenability of E. faecalis strains to acquisition of virulence factors was investigated along the occurrence of CRISPR associated (cas) genes. While distribution of most virulence factors, and RAPD versus MALDI-TOF-MS typing patterns were unrelated, 2 out of 5 RAPD clusters almost exclusively contained clinical E. faecalis isolates, and an occurrence of CRISPR elements versus reduced number of virulence factors was observed. The presence of the cytolysin operon, cob and as encoding pheromone and aggregation substance, respectively, significantly corresponded to absence of cas. As their production promote genetic exchange, their absence limits further gene acquisition and distribution. Thus, absence of the cytolysin operon, cob and as in a cas positive environment suggests itself as promising candidate for E. faecalis evaluation towards their occurrence in food fermentation or use as probiotics.
    Systematic and Applied Microbiology 09/2011; 34(8):553-60. · 3.31 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sourdough has played a significant role in human nutrition and culture for thousands of years and is still of eminent importance for human diet and the bakery industry. Lactobacillus sanfranciscensis is the predominant key bacterium in traditionally fermented sourdoughs.The genome of L. sanfranciscensis TMW 1.1304 isolated from an industrial sourdough fermentation was sequenced with a combined Sanger/454-pyrosequencing approach followed by gap closing by walking on fosmids. The sequencing data revealed a circular chromosomal sequence of 1,298,316 bp and two additional plasmids, pLS1 and pLS2, with sizes of 58,739 bp and 18,715 bp, which are predicted to encode 1,437, 63 and 19 orfs, respectively. The overall GC content of the chromosome is 34.71%. Several specific features appear to contribute to the ability of L. sanfranciscensis to outcompete other bacteria in the fermentation. L. sanfranciscensis contains the smallest genome within the lactobacilli and the highest density of ribosomal RNA operons per Mbp genome among all known genomes of free-living bacteria, which is important for the rapid growth characteristics of the organism. A high frequency of gene inactivation and elimination indicates a process of reductive evolution. The biosynthetic capacity for amino acids scarcely availably in cereals and exopolysaccharides reveal the molecular basis for an autochtonous sourdough organism with potential for further exploitation in functional foods. The presence of two CRISPR/cas loci versus a high number of transposable elements suggests recalcitrance to gene intrusion and high intrinsic genome plasticity.
    Microbial Cell Factories 08/2011; 10 Suppl 1:S6. · 4.25 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A total of 51 Lactobacillus sakei and 28 Lactobacillus curvatus strains from different origins were screened for their potential to produce biogenic amines (BAs), and for their diversity of peptidolytic systems and specific aminotransferases (AraT, BcaT) that initiate amino acid conversion to volatiles relevant for aroma formation in meat products. The profiles of volatiles formed (volatilomes) were analysed in the headspace of fermentations by solid phase microextraction followed by GC-MS analysis. Tyramine-forming potential was detected only within L. curvatus and was strain-dependent. Histamine decarboxylase (HDC) activity could only be detected in one L. sakei strain, previously described as histidine decarboxylase positive (HDC(+)). Peptide transporters and peptidases were nearly ubiquitous in L. sakei and only a few strains lacked single peptidases. In L. curvatus, differences were detected in the occurrence of peptidase genes detected with PCR primers derived from L. sakei. All strains lacked known aminotransferases specific for branched-chain amino acids (BCAAs) and aromatic amino acids (ACAAs). Although L. sakei is suggested as a genetically very heterogenous species, and relatedness between L. curvatus and L. sakei at the genomic level is rather low, they appeared to be nearly uniform in the genes forming the peptidolytic system. The volatilomes of L. sakei and L. curvatus strains were qualitatively nearly identical. However, slight differences in the formation of single volatile compounds and the interaction with staphylococci may impact upon sausage fermentation which occurs over a period of many weeks. Among the compounds expected to contribute to the aroma were dimethyldisulphide, 3-methyl-1-butanol, acetic acid, 1-butanol and butanoic acid.
    Systematic and Applied Microbiology 07/2011; 34(5):311-20. · 3.31 Impact Factor
  • Rudi F. Vogel, Matthias A. Ehrmann
    [Show abstract] [Hide abstract]
    ABSTRACT: Zusammenfassung Hoher Druck beeinflusst die Wechselwirkung von Makromolekülen, die an lebenswichtigen Funktionen von Mikroorganismen beteiligt sind. Er ist ein wertvolles thermodynamisches Werkzeug zur Untersuchung zellulärer Prozesse und eröffnet neue Wege zur Gestaltung hygienisch sicherer, naturbelassener Lebensmittel.
    BioSpektrum 05/2011; 17(3).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Lactobacillus sanfranciscensis LSCE1 was selected as a target organism originating from recurrently refreshed sourdough to study the metabolic rerouting associated with the acid stress exposure during sourdough fermentation. In particular, the acid stress induced a metabolic shift toward overproduction of 3-methylbutanoic and 2-methylbutanoic acids accompanied by reduced sugar consumption and primary carbohydrate metabolite production. The fate of labeled leucine, the role of different nutrients and precursors, and the expression of the genes involved in branched-chain amino acid (BCAA) catabolism were evaluated at pH 3.6 and 5.8. The novel application of the program XCMS to the solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) data allowed accurate separation and quantification of 2-methylbutanoic and 3-methylbutanoic acids, generally reported as a cumulative datum. The metabolites coming from BCAA catabolism increased up to seven times under acid stress. The gene expression analysis confirmed that some genes associated with BCAA catabolism were overexpressed under acid conditions. The experiment with labeled leucine showed that 2-methylbutanoic acid originated also from leucine. While the overproduction of 3-methylbutanoic acid under acid stress can be attributed to the need to maintain redox balance, the rationale for the production of 2-methylbutanoic acid from leucine can be found in a newly proposed biosynthesis pathway leading to 2-methylbutanoic acid and 3 mol of ATP per mol of leucine. Leucine catabolism to 3-methylbutanoic and 2-methylbutanoic acids suggests that the switch from sugar to amino acid catabolism supports growth in L. sanfranciscensis in restricted environments such as sourdough characterized by acid stress and recurrent carbon starvation.
    Applied and Environmental Microbiology 02/2011; 77(8):2656-66. · 3.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Lactic acid bacteria (LAB) are generally accepted as beneficial to the host and their presence is directly influenced by ingestion of fermented food or probiotics. While the intestinal lactic microbiota is well-described knowledge on its routes of inoculation and competitiveness towards selective pressure shaping the intestinal microbiota is limited. In this study, LAB were isolated from faecal samples of breast feeding mothers living in Syria, from faeces of their infants, from breast milk as well as from fermented food, typically consumed in Syria. A total of 700 isolates were characterized by genetic fingerprinting with random amplified polymorphic DNA (RAPD) and identified by comparative 16S rDNA sequencing and Matrix Assisted Laser Desorption Ionization-Time-Of-Flight Mass Spectrometry (MALDI-TOF-MS) analyses. Thirty six different species of Lactobacillus, Enterococcus, Streptococcus, Weissella and Pediococcus were identified. RAPD and MALDI-TOF-MS patterns allowed comparison of the lactic microbiota on species and strain level. Whereas some species were unique for one source, Lactobacillus plantarum, Lactobacillus fermentum, Pediococcus pentosaceus and Lactobacillus brevis were found in all sources. Interestingly, identical RAPD genotypes of L. plantarum, L. fermentum, L. brevis, Enterococcus faecium, Enterococcus faecalis and P. pentosaceus were found in the faeces of mothers, her milk and in faeces of her babies. Diversity of RAPD types found in food versus human samples suggests the importance of host factors in colonization and individual host specificity, and support the hypothesis that there is a vertical transfer of intestinal LAB from the mother's gut to her milk and through the milk to the infant's gut.
    Systematic and Applied Microbiology 02/2011; 34(2):148-55. · 3.31 Impact Factor
  • Matthias A. Ehrmann, Melanie Pavlovic
    Molekularbiologische Methoden in der Lebensmittelanalytik, Edited by Ulrich Busch, 01/2010: chapter 13: pages 221ff; Springer-Verlag., ISBN: 978-3642107153
  • [Show abstract] [Hide abstract]
    ABSTRACT: A Gram-stain-positive, catalase-negative and rod-shaped bacterium was isolated from a brewery environment. Its phylogenetic affiliation was determined by using 16S rRNA gene sequence analysis. It was found that strain TMW 1.1424(T) belongs to the genus Lactobacillus, with the three nearest neighbours Lactobacillus parabrevis LMG 11984(T) (97 %), Lactobacillus brevis DSM 20054(T) (95.9 %) and Lactobacillus hammesii DSM 16381(T) (96.2 %). Comparative sequencing of additional phylogenetic marker genes tuf and pheS confirmed the 16S rRNA gene sequence tree topology. The DNA G+C content of strain TMW 1.1424(T) is 46.6 mol%. Genomic DNA-DNA relatedness values with L. brevis DSM 20054(T), L. parabrevis LMG 11984(T) and L. hammesii DSM 16381(T) do not exceed 52.8 %, revealing that the novel isolate represents a separate genomic species. The strain can be distinguished from other related species of the genus Lactobacillus by physiological and biochemical tests. Based on biochemical, physiological and phylogenetic data, it is proposed that the new isolate be classified as a novel species of the genus Lactobacillus, Lactobacillus paucivorans sp. nov. The type strain is TMW 1.1424(T) (=DSM 22467(T) =LMG 25291(T)).
    International Journal of Systematic and Evolutionary Microbiology 11/2009; 60(Pt 10):2353-7. · 2.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: High hydrostatic pressure (HHP) is suggested to influence bacterial physiology by changing the structure and function of membranes and/or integral membrane proteins. In this work, the HHP-modulated dimerization behavior of the transmembrane regulatory protein ToxR from Photobacterium profundum SS9 was investigated, in response to changes in membrane organization induced by temperature and addition of phenethyl alcohol, in a background of different organisms (Escherichia coli and P. profundum) and mutants deficient in unsaturated fatty acid synthesis. Reporter strains were constructed by chromosomal integration of an ompL-promoter lacZ fusion cassette. Arabinose-controlled ToxR expression was achieved by plasmid pBADK-ToxR-his. The results demonstrate that changes in the lipid environment have a marginal effect on the function of ToxR; instead, ToxR activity appears to be largely determined by the properties of the protein itself.
    High Pressure Research 09/2009; 29(3):431-442. · 0.93 Impact Factor
  • Matthias A Ehrmann, Simone Freiding, Rudi F Vogel
    [Show abstract] [Hide abstract]
    ABSTRACT: A novel lactic acid bacterium, strain TMW 2.694(T), was isolated among other lactic acid bacteria from palm wine, an alcoholic beverage produced from the sap of various palm tree species. Strain TMW 2.694(T) is a Gram-positive, facultatively anaerobic, catalase-negative, non-spore-forming coccus, occurring in long chains. Phylogenetic analysis based on 16S rRNA gene sequencing positioned strain TMW 2.694(T) in a distinct line of descent within the genus Leuconostoc, with the closest neighbours being Leuconostoc lactis JCM 6123(T) (98.7 % sequence similarity) and Leuconostoc citreum DSM 5577(T) (98.8 % sequence similarity). Comparative sequencing of the additional phylogenetic markers dnaK and recA confirmed the 16S rRNA gene tree topology. Genomic DNA-DNA similarities of strain TMW 2.694(T) to L. lactis DSM 20202(T) and L. citreum DSM 5577(T) were 45.1 and 17.7 %, respectively. The DNA G+C content is 36.4 mol%. Thus, we propose a novel species within the genus Leuconostoc, with the name Leuconostoc palmae sp. nov. and the type strain TMW 2.694(T) (=DSM 21144(T) =LMG 24510(T)).
    International Journal of Systematic and Evolutionary Microbiology 06/2009; 59(Pt 5):943-7. · 2.80 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: High hydrostatic pressure (HHP) is suggested to influence the structure and function of membranes and/or integrated proteins. We demonstrate for the first time HHP-induced dimer dissociation of membrane proteins in vivo with Vibrio cholerae ToxR variants in Escherichia coli reporter strains carrying ctx::lacZ fusions. Dimerization ceased at 20 to 50 MPa depending on the nature of the transmembrane segments rather than on changes in the ToxR lipid bilayer environment.
    Applied and Environmental Microbiology 11/2008; 74(24):7821-3. · 3.95 Impact Factor
  • R F Vogel, K Linke, H Teichert, M A Ehrmann
    [Show abstract] [Hide abstract]
    ABSTRACT: Cellular membranes serve in the separation of compartments, recognition of the environment, selective transport and signal transduction. Membrane lipids and membrane proteins play distinct roles in these processes, which are affected by environmental chemical (e. g. pH) or physical (e. g. pressure and temperature) changes. High hydrostatic pressure (HHP) affects fluidity and integrity of bacterial membranes instantly during the ramp, resulting in a loss of membrane potential and vital membrane protein functions. We have used the multiple drug transporter LmrA from Lactococcus lactis and ToxR, a membrane protein sensor from Photobacterium profundum, a deep-sea bacterium, and Vibrio cholerae to study membrane protein interaction and functionality in proteolioposomes and by the use of in vivo reporter systems, respectively. Both proteins require dimerization in the phospholipid bilayer for their functionality, which was favoured in the liquid crystalline lipid phase with ToxR and LmrA. Whereas LmrA, which resides in liposomes consisting of DMPC, DMPC/cholesterol or natural lipids, lost its ATPase activity above 20 or 40 MPa, it maintained its active dimeric structure in DOPC/DPPC/cholesterol liposomes up to 120 MPa. By using a specific indicator strain in which the dimerisation of ToxR initiates the transcription of lacZ it was demonstrated, that the amino acid sequence of the transmembrane domain influences HHP stability of ToxR dimerization in vivo. Thus, both the lipid structure and the nature of the protein affect membrane protein interaction. It is suggested that the protein structure determines basic functionality, e.g. principle ability or kinetics to dimerize to a functional complex, while the lipid environment modulates this property.
    Journal of Physics Conference Series 07/2008; 121(11):112005.

Publication Stats

1k Citations
149.67 Total Impact Points


  • 1996–2013
    • Technische Universität München
      • • Chair of Technical Microbiology
      • • Department of Microbiology
      München, Bavaria, Germany
  • 2008
    • Technische Universität Dortmund
      Dortmund, North Rhine-Westphalia, Germany
  • 2006
    • Technische Universität Berlin
      Berlín, Berlin, Germany
  • 2005
    • University of Alberta
      • Department of Agricultural, Food, and Nutritional Science
      Edmonton, Alberta, Canada