Ralf Dieckmann

Bundesinstitut für Risikobewertung | BfR · Department of Biological Safety

Phenotypic susceptibility testing of Escherichia (E.) coli is an essential tool to gain a better understanding of the potential impact of biocide selection pressure on antimicrobial resistance. We, therefore, determined the biocide and antimicrobial susceptibility of 216 extended-spectrum β-lactamase-producing (ESBL) and 177 non-ESBL E. coli isolat...

Disinfection is a key strategy to reduce the burden of infections. The contact of bacteria to biocides—the active substances of disinfectants—has been linked to bacterial adaptation and the development of antimicrobial resistance. Currently, there is no scientific consensus on whether the excessive use of biocides contributes to the emergence and s...

Biocides are essential to prevent foodborne zoonotic diseases. However, concerns have been raised that their use may contribute to the development and spread of antibiotic resistant bacteria along the food production chain and in healthcare settings. In the research project BiozAR, we investigate the susceptibility of the indicator organism E. coli...

Introduction. Biocides have been applied as disinfectants for decades and play a major role in the prevention of zoonotic diseases in healthcare settings and the food production chain. However, concerns have been raised that their use may contribute to the development and spread of antibiotic resistant bacteria. Therefore, we investigated the susce...

Biocides are frequently applied as disinfectants in animal husbandry to prevent the transmission of drug-resistant bacteria and to control zoonotic diseases. Concerns have been raised, that their use may contribute to the selection and persistence of antimicrobial-resistant bacteria. Especially, extended-spectrum β-lactamase- and AmpC β-lactamase-p...

Brucellosis is one of the most common bacterial zoonoses worldwide affecting not only livestock and wildlife but also pets. Canine brucellosis is characterized by reproductive failure in dogs. Human Brucella canis infections are rarely reported but probably underestimated due to insufficient diagnostic surveillance. To improve diagnostics, we inves...

The skin`s microbiome is predominantly commensalic, harbouring a metabolic potential far exceeding that of its host. While there is clear evidence that bacteria-dependent metabolism of pollutants modulates the toxicity for the host there is still a lack of models for investigating causality of microbiome-associated pathophysiology or toxicity. We n...

Brucellosis is still a global health issue, and surveillance and control of this zoonotic disease in livestock remains a challenge. Human outbreaks are mainly linked to the consumption of unpasteurized dairy products. The detection of human pathogenic Brucella species in food of animal origin is time-consuming and laborious. Bacteriophages are broa...

Due to its high case fatality rate, foodborne listeriosis is considered a major public health concern worldwide. We describe one of the largest listeriosis outbreaks in Germany with 83 cases of invasive listeriosis between 2013 and 2018. As part of the outbreak investigation, we identified a highly diverse Listeria monocytogenes population at a sin...

The objective of our study was to investigate the effects of benzalkonium chloride (BC) adaptation of L. monocytogenes on the susceptibility to antimicrobial agents and on the viable but non culturable (VBNC) state of the bacterial cells. We adapted L. monocytogenes SLCC2540 to BC by applying BC below minimum inhibitory concentration (MIC) to above...

Foodborne pathogens such as L. monocytogenes can persist in food production environments for a long time, causing perennial outbreaks. Hence, bacterial pathogens are able to survive cleaning and disinfection procedures. Accordingly, they may be repeatedly exposed to sublethal concentrations of disinfectants, which might result in bacterial adaptati...

We investigated 543 Listeria monocytogenes isolates from food having a temporal and spatial distribution compatible with that of the invasive listeriosis outbreak occurring 2012–2016 in southern Germany. Using forensic microbiology, we identified several products from 1 manufacturer contaminated with the outbreak genotype. Continuous molecular surv...

Maximum parsimony tree of Listeria monocytogenes isolates collected in Bavaria, Baden-Württemberg, and Hesse, Germany, 2012–2016.

Despite huge efforts to combat foodborne bacterial pathogens, the number of foodborne infections remains high throughout the world. Culture-dependent gold standard detection methods with their tedious and time-consuming procedures have approached their limits whereas the use of rapid and user-friendly alternative methods is on the rise. Validation...

Background: Tattooing is a globally growing trend. Overall prevalence among adults in industrialized countries is around 10-20%. Given the high and increasing numbers of tattooed people worldwide, medical and public health implications emerging from tattooing trends require greater attention not only by the public, but also by medical professional...

Yersinia enterocolitica, Y. pseudotuberculosis and Y. pestis are pathogens of major medical importance, which are responsible for a considerable number of infections every year. The detection of these species still relies on cultural methods, which are slow, labour intensive and often hampered by the presence of high amounts of accompanying flora....

Vibrio vulnificus is a halophilic bacterium of coastal environments known for sporadically causing severe foodborne or wound infections. Global warming is expected to lead to a rising occurrence of V. vulnificus and an increasing incidence of human infections in Northern Europe. So far, infections in Germany were exclusively documented for the Balt...

Microbiological monitoring of consumer products and the efficiency of early warning systems and outbreak investigations depend on the rapid identification and strain characterisation of pathogens posing risks to the health and safety of consumers. This study evaluated the potential of three rapid analytical techniques for identification and subtypi...

Efficient preparation of food samples, comprising sampling and homogenization, for microbiological testing is an essential, yet largely neglected, component of foodstuff control. Salmonella enterica spiked chicken breasts were used as a surface contamination model whereas salami and meat paste acted as models of inner-matrix contamination. A system...

In 2013, contaminated liquid soap was detected by routine microbiological monitoring of consumer products through state health authorities. Because of its high load of Klebsiella oxytoca, the liquid soap was notified via the European Union Rapid Alert System for Dangerous Non-Food Products (EU-RAPEX) and recalled. Here, we present two draft genome...

The production of bioactive polypeptides (peptaibiotics) in vivo is a sophisticated adaptation strategy of both mycoparasitic and saprotrophic Trichoderma species for colonizing and defending their natural habitats. This feature is of major practical importance, as the detection of peptaibiotics in plant-protective Trichoderma species, which are su...

Vibrio parahaemolyticus is a recognized human enteropathogen. Thermostable direct he- molysin (TDH) and TDH-related hemolysin (TRH) as well as the type III secretion system 2 (T3SS2) are considered as major virulence factors. As tdh positive strains are not detected in coastal waters of Germany, we focused on the characterization of trh positive st...

Foodborne pathogens cause millions of infections every year and are responsible for considerable economic losses worldwide. The current gold standard for the detection of bacterial pathogens in food is still the conventional cultivation following standardized and generally accepted protocols. However, these methods are time-consuming and do not pro...

Vibrio furnissii and Vibrio fluvialis are two closely related species which are regarded as emerging human pathogens. Human infections have been mainly associated with consumption of seafood or drinking of contaminated water. V. furnissii strains can be distinguished from V. fluvialis by their ability to produce gas from fermentation of carbohydrat...

Vibrio cholerae belonging to the non-O1, non-O139 serogroups are present in the coastal waters of Germany and in some German and Austrian lakes. These bacteria can cause gastroenteritis and extraintestinal infections, and are transmitted through contaminated food and water. However, non-O1, non-O139 V. cholerae infections are rare in Germany. We st...

Vibrio parahaemolyticus is a recognized enteropathogen causing diarrhea in humans and is a one of the major causes of seafoodborne gastroenteritis. An important virulence factor is thermostable direct hemolysin (TDH), a pore-forming toxin, which is able to lyse eukaryotic cells. The active toxin is a tetramer of four identical protein subunits, whi...

The genetic diversity of Vibrio vulnificus isolates from clinical and environmental sources originating from the Baltic Sea region was evaluated by Multilocus sequence typing and possible relationships between MLST clusters, potential genotypic and phenotypic traits associated with pathogenicity and source of isolation were investigated. The studie...

Shiga toxin 2 (Stx2)-producing Escherichia coli (STEC) O104:H4 caused one of the world's largest outbreaks of hemorrhagic colitis and hemolytic uremic syndrome in Germany in 2011. These strains have evolved from enteroaggregative E. coli (EAEC) by the acquisition of the Stx2 genes and have been designated enteroaggregative hemorrhagic E. coli. Nucl...

The most common sequences of peptaibiotics are 11-residue peptaibols found widely distributed in the genus Trichoderma/Hypocrea. Frequently associated are 14-residue peptaibols sharing partial sequence identity. Genome sequencing projects of three Trichoderma strains of the major clades reveal the presence of up to three types of nonribosomal pepti...

Vibrio is a genus of bacteria present in surface and coastal waters as well as in marine organisms worldwide. In many countries, pathogenic Vibrio species are a main cause of bacterial diarrhea, which may result from comsumption of contaminated seafood and fish products or from drinking contaminated water. Vibrio infections may also gain in importa...

Vibrionen sind salzliebende Bakterien, die in Oberflächen- und Küstengewässern sowie Meerestieren weltweit verbreitet sind. In vielen Ländern stellen pathogene Vibrio-Spezies eine der Hauptursachen von bakteriell verursachten Durchfallerkrankungen dar, die durch den Verzehr von kontaminierten Meeresfrüchten und Fischprodukten und durch verseuchtes...

The chromosomal ail gene (attachment and invasion locus) is commonly used as target gene for the detection of pathogenic Y. enterocolitica strains in food testing. The ail PCR does not detect strains of biotype 1A (BT1A), which are regarded as non-pathogenic because BT1A strains lack the virulence plasmid and chromosomally encoded virulence genes....

Currently, 2,610 different Salmonella serovars have been described according to the White-Kauffmann-Le Minor scheme. They are routinely differentiated by serotyping, which is based on the antigenic variability at lipopolysaccharide moieties (O antigens), flagellar proteins (H1 and H2 antigens), and capsular polysaccharides (Vi antigens). The aim of...

Yersinia are Gram-negative, rod-shaped facultative anaerobes, and some of them, Yersinia enterocolitica, Yersinia pseudotuberculosis, and Yersinia pestis, are pathogenic in humans. Rapid and accurate identification of Yersinia strains is essential for appropriate therapeutic management and timely intervention for infection control. In the past deca...

Vibrio identification by means of traditional microbiological methods is time consuming because of the many biochemical tests that have to be performed to distinguish closely related species. This work aimed at evaluating the use of MALDI-TOF mass spectrometry for the rapid identification of Vibrio (V.) spp. as an advantageous application to rapidl...

Hydrophobins are small extracellular proteins, unique to and ubiquitous in filamentous fungi, which mediate interactions between the fungus and environment. The mycoparasitic fungus Hypocrea atroviridis has recently been shown to possess 10 different class II hydrophobin genes, which is a much higher number than that of any other ascomycete investi...

Variations in the mass spectral profiles of multiple housekeeping proteins of 126 strains representing Salmonella enterica subsp. enterica (subspecies I), S. enterica subsp. salamae (subspecies II), S. enterica subsp. arizonae (subspecies IIIa), S. enterica subsp. diarizonae (subspecies IIIb), S. enterica subsp. houtenae (subspecies IV), and S. ent...

The bacterial strain Gp_4_7.1T, isolated from the marine sponge Isops phlegraei collected at the Sula Ridge off the Norwegian coast, was characterized. The isolate was a motile spirillum that was monopolarly and monotrichously flagellated. It was aerobic, Gram-negative, oxidase-positive and catalase-negative. Optimal growth occurred between 20 and...

The Brevicompactum clade is recognized as a separate lineage in Trichoderma/Hypocrea. This includes T. brevicompactum and the new species T. arundinaceum, T. turrialbense, T. protrudens and Hypocrea rodmanii. The closest relative of the Brevicompactum clade is the Lutea clade. With the exception of H. rodmanii, all members of this clade produce the...

The polymerase chain reaction (PCR) is one of the most important rapid methods for the sensitive and specific detection of pathogenic and spoilage microorganisms. The method is increasingly applied in surveillance and monitoring programs to detect pathogens, especially for ensuring the safety and quality of food. The food-borne pathogen Salmonella...

Strain HAL40b(T) was isolated from the marine sponge Haliclona sp. 1 collected at the Sula Ridge off the Norwegian coast and characterized by physiological, biochemical and phylogenetic analyses. The isolate was a small rod with a polar flagellum. It was aerobic, Gram-negative and oxidase- and catalase-positive. Optimal growth was observed at 20-30...

Species of the mycoparasitic fungal genus Hypocrea/Trichoderma are prominent producers of peptaibols, a class of small linear peptides of fungal origin. Some of these peptaibols have been shown to act synergistically with cell-wall-degrading enzymes in the inhibition of the growth of other fungi in vitro and in vivo. Here we present the structure o...

Peptaibols are characteristic linear alpha-aminoisobutyrate-containing peptides produced by certain Ascomycetes, especially of the genus Hypocrea/Trichoderma [Hypocrea and Trichoderma are the names for the teleo- and anamorph forms of the same taxon; where known to occur in nature, the teleomorph is used to name the species. To aid the inexperience...

Fungi of the genus Sepedonium (anamorphic ascomycetes) are known to infect fruiting bodies of Basidiomycetes of the order Boletales. We have characterized twelve Sepedonium isolates by intact-cell mass spectrometry (IC-MS) with the help of respective biomarkers and their metabolite spectra focusing on peptaibol production. A strain of mycoparasitic...

Intact-cell MS (ICMS) was applied for the direct detection of hydrophobins in various species and strains of Hypocrea/Trichoderma. In both mycelia and spores, dominating peaks were identified as hydrophobins by detecting mass shifts of 8 Da of reduced and unreduced forms, the analysis of knockout mutants, and comparison with protein databases. Stra...

A nonribosomal peptide synthetase (NRPS) in Schizosaccharomyces pombe, which possesses an unusual structure incorporating three adenylation domains, six thiolation domains and six condensation domains, has been shown to produce the cyclohexapeptide siderophore ferrichrome. One of the adenylation domains is truncated and contains a distorted key mot...

Tyrocidine synthetase 1 (TY1), the initial monomodular constituent of the tyrocidine biosynthetic system, exhibits relaxed substrate specificity, however an efficient editing of the mis-activated amino acid provides for fidelity of product formation. We chose to analyse the consequence of single amino acid substitutions, in the amino acid activatio...

Despite their great variability, particularly of color, Mediterranean specimens of the genus Cystodytes are usually attributed to the cosmopolitan species Cystodytes dellechiajei. In this study, we used MALDI-TOF and HPLC techniques to assess alkaloid distribution in the four most abundant color morphs of Cystodytes in the western Mediterranean (gr...

Rapid grouping of bacterial isolates is critical in comprehensive microbial studies of environmental samples or screening programmes e.g. in unknown marine environments where large numbers of strains have to be isolated on different growth media. Sets of bacteria have been cultured from the marine sponges Isops phlegraei, Haliclona sp. 1, Phakellia...

Hassallidin A (1), a new antifungal glycosylated lipopeptide, was isolated from an epilithic cyanobacterium collected in Bellano, Italy, identified as Tolypothrix (basionym Hassallia) species. Chemical, mass spectrometric, and spectroscopic analyses, including one- and two-dimensional NMR, were performed to determine an esterified eight-residue cyc...

Alkaline phosphatase (AP) displays significant structural changes during metal-ion binding, supporting cooperative interactions between the subunits of the dimeric enzyme. Here, we present data on the dynamic properties of AP from E. coli, and characterize the structural changes that accompany variations in metal-ion content, combining limited prot...

The biosynthesis of algicides produced by a novelFischerellastrain was investigated. Two allelochemicals were identified, the aminoacylpolyketide fischerellin A (FsA) and the alkaloid 12-epi-hapalindole F (HapF). Based on the structure of FsA, genes that could be involved in its biosynthesis, including those encoding nonribosomal peptide synthetase...

applications of MALDI-TOF mass spectrometry in the analysis of sponge and bacterial metabolites and the dereplication of bacterial isolates from boreal sponges

Adenylation domains of non-ribosomal peptide synthetases (NRPS) catalyse the formation of aminoacyl adenylates, and in addition synthesize mono- and dinucleoside polyphosphates. Here, we show that NRPS systems furthermore contain an ATPase activity in the range of up to 2 P(i)/min. The hydrolysis rate by apo-tyrocidine synthetase 1 (apo-TY1) is enh...

potential drugs of marine origin marine symbionts as drug producers a north atlantic sponge community new efficient screenng methods sponge associated bacteria bacteria from marine sediments

This study represents the microbiological part of the BOSMAN project (Boreal Sponges; Sources of Marine Natural Products) and investigates the diversity of bacteria associated with sponges from boreal deep water regions. A variety of sponges were collected from the Sula Ridge and the shelf off the Norwegian coast with the aim to identify and charac...

delta-(L-alpha-Aminoadipyl)-L-cysteinyl-D-valine synthetase (ACVS) catalyses, via the protein thiotemplate mechanism, the nonribosomal biosynthesis of the penicillin and cephalosporin precursor tripeptide delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV). The complete and fully saturated biosynthetic system approaches maximum rate of product g...

Introduction Historical Outline Erythromycin Biosynthesis The Erythromycin Gene Cluster The DEBS‐Proteins The Biosynthetic Gene Cluster for Rapamycin Other Modular Polyketide Synthases NRPS/PKS Hybrids Generation of Novel Polyketides via Genetic Engineering Relocation of the Thioesterase Domain Domain Swapping Recombination of Modules O...

A new indole derivative representing a condensation product of 6-bromotryptophan and arginine is the major diketopiperazine produced by the sponge Geodia baretti. Strong evidence is provided that this compound represents the correct structure of barettin, which had been described earlier.

A deletion mutant of tyrocidine synthetase 1 (DeltaDeltaTY1), comprising the adenylation domain of TY1 as an independent functional adenylate-forming unit, was used to investigate the ability of the adenylation domain in non-ribosomal peptide synthetases to catalyse peptide bond formation from the aminoacyl adenylate intermediate. The results demon...

In response to nutritional stress conditions, Bacillus brevis produces the cyclodecapeptide antibiotic tyrocidine via tyrocidine synthetase, a multifunctional non-ribosomal peptide synthetase. The apo-form of tyrocidine synthetase 1 forms adenosine (5′)tetraphospho(5′)adenosine, when incubated with MgATP2−, amino acid and inorganic pyrophosphatase....

Background and purpose: Peptide synthetases are multifunctional enzyme complexes catalysing the non-ribosomal biosynthesis of a variety of bioactive peptide products. The activation reaction is generally monitored using the isotope exchange assay which suffers several disadvantages such as discontinuous monitoring and the use of radioactive reagent...

How genes are expressed and translated into proteins (using mRNA, codons and tRNAs as adaptor molecules) forms the basis of the 'genetic code'. Many peptides are synthesized nonribosomally, however, by large protein complexes that also serve as templates. Recent advances have shed light on what the nonribosomal code is and how it can be read.

Non-ribosomally formed peptides display both highly conserved and variable amino acid positions, the variations leading to a wide range of peptide families. Activation of the amino acid substrate proceeds in analogy to the ribosomal biosynthetic mechanism generating aminoacyl adenylate and acyl intermediates. To approach the mechanism of fidelity o...

The boundaries of the structural domains in peptide synthetases and the conformational changes related to catalysis were investigated by limited proteolysis of tyrocidine synthetase 1 (TY1). Four regions sensitive to proteolysis were detected (cleavage site at Arg13, Arg424, Arg509 and Arg602) that, in addition to an N-terminal extension, accuratel...