• Beta-lactam resistance response triggered by inactivation of a nonessential penicillin-binding protein.

      Moya, Bartolomé; Dötsch, Andreas; Juan, Carlos; Blázquez, Jesús; Zamorano, Laura; Haussler, Susanne; Oliver, Antonio; Servicio de Microbiología and Unidad de Investigación, Hospital Son Dureta, Instituto Universitario de Investigación en Ciencias de la Salud Palma de Mallorca, Spain. (2009-03)
      It has long been recognized that the modification of penicillin-binding proteins (PBPs) to reduce their affinity for beta-lactams is an important mechanism (target modification) by which Gram-positive cocci acquire antibiotic resistance. Among Gram-negative rods (GNR), however, this mechanism has been considered unusual, and restricted to clinically irrelevant laboratory mutants for most species. Using as a model Pseudomonas aeruginosa, high up on the list of pathogens causing life-threatening infections in hospitalized patients worldwide, we show that PBPs may also play a major role in beta-lactam resistance in GNR, but through a totally distinct mechanism. Through a detailed genetic investigation, including whole-genome analysis approaches, we demonstrate that high-level (clinical) beta-lactam resistance in vitro, in vivo, and in the clinical setting is driven by the inactivation of the dacB-encoded nonessential PBP4, which behaves as a trap target for beta-lactams. The inactivation of this PBP is shown to determine a highly efficient and complex beta-lactam resistance response, triggering overproduction of the chromosomal beta-lactamase AmpC and the specific activation of the CreBC (BlrAB) two-component regulator, which in turn plays a major role in resistance. These findings are a major step forward in our understanding of beta-lactam resistance biology, and, more importantly, they open up new perspectives on potential antibiotic targets for the treatment of infectious diseases.
    • Biogeography and Environmental Drivers of Abundance and Genotype Composition Across the West Bank: Relevance of a Genotype-Based Ecology for Understanding Occurrence.

      Zayed, Ashraf R; Butmeh, Suha; Pecellin, Marina; Salah, Alaa; Alalam, Hanna; Steinert, Michael; Höfle, Manfred G; Bitar, Dina M; Brettar, Ingrid; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-12-01)
      The West Bank can be considered as a high-risk area for Legionella prevalence in drinking water due to high ambient temperature, intermittent water supply, frequent pressure loss, and storage of drinking water in roof containers. To assess occurrence of Legionella species, especially L. pneumophila, in the drinking water of the West Bank, the drinking water distribution systems of eight hospitals were sampled over a period of 2.3 years covering the seasonal cycle and the major geographic regions. To gain insight into potential environmental drivers, a set of physico-chemical and microbiological parameters was recorded. Sampling included drinking water and biofilm analyzed by culture and PCR-based methods. Cultivation led to the isolation of 180 strains of L. pneumophila that were genotyped by Multi-Locus Variable Number of Tandem Repeat Analysis (MLVA). Surprisingly, the abundance of culturable L. pneumophila was low in drinking water of the sampling sites, with only three out of eight sites where Legionella was observed at all (range: 30-500 CFU/liter). By contrast, biofilm and PCR-based analyses showed a higher prevalence. Statistical analyses with physico-chemical parameters revealed a decrease of L. pneumophila abundance for water and biofilm with increasing magnesium concentrations (>30 mg/l). MLVA-genotype analysis of the L. pneumophila isolates and their spatial distribution indicated three niches characterized by distinct physico-chemical parameters and inhabited by specific consortia of genotypes. This study provides novel insights into mechanisms shaping L. pneumophila populations and triggering their abundance leading to an understanding of their genotype-specific niches and ecology in support of improved prevention measures.
    • Breaking the vicious cycle of antibiotic killing and regrowth of biofilm-residing .

      Müsken, Mathias; Pawar, Vinay; Schwebs, Timo; Bähre, Heike; Felgner, Sebastian; Weiss, Siegfried; Häussler, Susanne; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (2018-10-08)
      Biofilm-residing bacteria embedded in an extracellular matrix are protected from diverse physico-chemical insults. In addition to the general recalcitrance of biofilm-bacteria, high bacterial loads in biofilm-associated infections significantly diminishes the efficacy of antimicrobials due to a low per-cell antibiotic concentration. Accordingly, present antimicrobial treatment protocols, that have been established to serve the eradication of acute infections, fail to clear biofilm-associated chronic infections. In the present study, we applied automated confocal microscopy on Pseudomonas aeruginosa to monitor dynamic killing of biofilm-grown bacteria by tobramycin and colistin in real-time. We revealed that the time required for surviving bacteria to repopulate the biofilm could be taken as measure for effectiveness of the antimicrobial treatment. It depends on the: i) nature and concentration of the antibiotic, ii) duration of antibiotic treatment; iii) application as mono or combination therapy and iv) time intervals of drug administration. The vicious cycle of killing and repopulation of biofilm bacteria could also be broken in an in vivo model system by applying successive antibiotic dosages with time intervals that do not allow full reconstitution of the biofilm communities. Treatment regimens that consider the important aspects of antimicrobial killing kinetics bear the potential to improve control of biofilm regrowth. This is an important and underestimated factor that is bound to ensure sustainable treatment success of chronic infections.
    • Broad host range vectors for expression of proteins with (Twin-) Strep-tag, His-tag and engineered, export optimized yellow fluorescent protein

      Dammeyer, Thorben; Timmis, Kenneth N; Tinnefeld, Philip (2013-05-20)
      Abstract Background In current protein research, a limitation still is the production of active recombinant proteins or native protein associations to assess their function. Especially the localization and analysis of protein-complexes or the identification of modifications and small molecule interaction partners by co-purification experiments requires a controllable expression of affinity- and/or fluorescence tagged variants of a protein of interest in its native cellular background. Advantages of periplasmic and/or homologous expressions can frequently not be realized due to a lack of suitable tools. Instead, experiments are often limited to the heterologous production in one of the few well established expression strains. Results Here, we introduce a series of new RK2 based broad host range expression plasmids for inducible production of affinity- and fluorescence tagged proteins in the cytoplasm and periplasm of a wide range of Gram negative hosts which are designed to match the recently suggested modular Standard European Vector Architecture and database. The vectors are equipped with a yellow fluorescent protein variant which is engineered to fold and brightly fluoresce in the bacterial periplasm following Sec-mediated export, as shown from fractionation and imaging studies. Expression of Strep-tag®II and Twin-Strep-tag® fusion proteins in Pseudomonas putida KT2440 is demonstrated for various ORFs. Conclusion The broad host range constructs we have produced enable good and controlled expression of affinity tagged protein variants for single-step purification and qualify for complex co-purification experiments. Periplasmic export variants enable production of affinity tagged proteins and generation of fusion proteins with a novel engineered Aequorea-based yellow fluorescent reporter protein variant with activity in the periplasm of the tested Gram-negative model bacteria Pseudomonas putida KT2440 and Escherichia coli K12 for production, localization or co-localization studies. In addition, the new tools facilitate metabolic engineering and yield assessment for cytoplasmic or periplasmic protein production in a number of different expression hosts when yields in one initially selected are insufficient.
    • Broad host range vectors for expression of proteins with (Twin-) Strep-tag, His-tag and engineered, export optimized yellow fluorescent protein.

      Dammeyer, Thorben; Timmis, Kenneth N; Tinnefeld, Philip; Institut für Physikalische und Theoretische Chemie, NanoBioSciences, Technische Universität Braunschweig, Hans Sommer Str, 10, Braunschweig 38106, Germany. T.Dammeyer@tu-braunschweig.de (2013)
      In current protein research, a limitation still is the production of active recombinant proteins or native protein associations to assess their function. Especially the localization and analysis of protein-complexes or the identification of modifications and small molecule interaction partners by co-purification experiments requires a controllable expression of affinity- and/or fluorescence tagged variants of a protein of interest in its native cellular background. Advantages of periplasmic and/or homologous expressions can frequently not be realized due to a lack of suitable tools. Instead, experiments are often limited to the heterologous production in one of the few well established expression strains.
    • Budesonide in Autoimmune Hepatitis: The Right Drug at the Right Time for the Right Patient.

      Manns, Michael P; Jaeckel, Elmar; Taubert, Richard; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-11-08)
    • C-Type Lectin Receptor (CLR)-Fc Fusion Proteins As Tools to Screen for Novel CLR/Bacteria Interactions: An Exemplary Study on Preselected Isolates.

      Mayer, Sabine; Moeller, Rebecca; Monteiro, João T; Ellrott, Kerstin; Josenhans, Christine; Lepenies, Bernd; TWINCORE, Zentrum für experimentelle und klinische Infektionsforschung GmbH,Feodor-Lynen Str. 7, 30625 Hannover, Germany. (2018-01-01)
      C-type lectin receptors (CLRs) are carbohydrate-binding receptors that recognize their ligands often in a Ca2+-dependent manner. Upon ligand binding, myeloid CLRs in innate immunity trigger or inhibit a variety of signaling pathways, thus initiating or modulating effector functions such as cytokine production, phagocytosis, and antigen presentation. CLRs bind to various pathogens, including viruses, fungi, parasites, and bacteria. The bacterium Campylobacter jejuni (C. jejuni) is a very frequent Gram-negative zoonotic pathogen of humans, causing severe intestinal symptoms. Interestingly, C. jejuni expresses several glycosylated surface structures, for example, the capsular polysaccharide (CPS), lipooligosaccharide (LOS), and envelope proteins. This “Methods” paper describes applications of CLR–Fc fusion proteins to screen for yet unknown CLR/bacteria interactions using C. jejuni as an example. ELISA-based detection of CLR/bacteria interactions allows a frst prescreening that is further confrmed by flow cytometry-based binding analysis and visualized using confocal microscopy. By applying these methods, we identifed Dectin-1 as a novel CLR recognizing two selected C. jejuni isolates with different LOS and CPS genotypes. In conclusion, the heredescribed applications of CLR–Fc fusion proteins represent useful methods to screen for and identify novel CLR/bacteria interactions.
    • C-X-C Motif Chemokine Receptor 4 Blockade Promotes Tissue Repair After Myocardial Infarction by Enhancing Regulatory T Cell Mobilization and Immune-Regulatory Function.

      Wang, Yong; Dembowsky, Klaus; Chevalier, Eric; Stüve, Philipp; Korf-Klingebiel, Mortimer; Lochner, Matthias; Napp, L Christian; Frank, Heike; Brinkmann, Eva; Kanwischer, Anna; et al. (Lippinscott, Williams & Wilkins; American Heart Association, 2019-01-30)
      Acute myocardial infarction (MI) elicits an inflammatory response that drives tissue repair and adverse cardiac remodeling. Inflammatory cell trafficking after MI is controlled by C X-C motif chemokine ligand 12 (CXCL12) and its receptor, C-X-C motif chemokine receptor 4 (CXCR4). CXCR4 antagonists mobilize inflammatory cells and promote infarct repair, but the cellular mechanisms are unclear. We investigated the therapeutic potential and mode of action of the peptidic macrocycle CXCR4 antagonist POL5551 in mice with reperfused MI. We applied cell depletion and adoptive transfer strategies using lymphocyte-deficient Rag1 knockout mice; DEREG mice, which express a diphtheria toxin receptor-enhanced green fluorescent protein fusion protein under the control of the promoter/enhancer region of the regulatory T (T Intraperitoneal POL5551 injections in wild-type mice (8 mg/kg at 2, 4, 6, and 8 d) enhanced angiogenesis in the infarct border-zone, reduced scar size, and attenuated left ventricular remodeling and contractile dysfunction at 28 d. Treatment effects were absent in splenectomized wild-type mice, Rag1 knockout mice, and T Our data confirm CXCR4 blockade as a promising treatment strategy after MI. We identify dendritic cell-primed splenic T
    • Carbon source-dependent inhibition of xyl operon expression of the Pseudomonas putida TOL plasmid.

      Holtel, A; Marqués, S; Möhler, I; Jakubzik, U; Timmis, K N (1994-03)
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    • Care of patients with liver disease during the COVID-19 pandemic: EASL-ESCMID position paper.

      Boettler, Tobias; Newsome, Philip N; Mondelli, Mario U; Maticic, Mojca; Cordero, Elisa; Cornberg, Markus; Berg, Thomas; CiiM, Zentrum für individualisierte Infektionsmedizin, Feodor-Lynen-Str.7, 30625 Hannover. (Elsevier, 2020-04-02)
      The coronavirus disease 2019 (COVID-19) pandemic poses an enormous challenge to healthcare systems in affected communities. Older patients and those with pre-existing medical conditions have been identified as populations at risk of a severe disease course. It remains unclear at this point to what extent chronic liver diseases should be considered as risk factors, due to a shortage of appropriate studies. However, patients with advanced liver disease and those after liver transplantation represent vulnerable patient cohorts with an increased risk of infection and/or a severe course of COVID-19. In addition, the current pandemic requires unusual allocation of healthcare resources which may negatively impact the care of patients with chronic liver disease that continue to require medical attention. Thus, the challenge hepatologists are facing is to promote telemedicine in the outpatient setting, prioritise outpatient contacts, avoid nosocomial dissemination of the virus to patients and healthcare providers, and at the same time maintain standard care for patients who require immediate medical attention.
    • Catalytically Active Cas9 Mediates Transcriptional Interference to Facilitate Bacterial Virulence.

      Ratner, Hannah K; Escalera-Maurer, Andrés; Le Rhun, Anaïs; Jaggavarapu, Siddharth; Wozniak, Jessie E; Crispell, Emily K; Charpentier, Emmanuelle; Weiss, David S; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Elsevier; Cell Press, 2019-06-24)
      In addition to defense against foreign DNA, the CRISPR-Cas9 system of Francisella novicida represses expression of an endogenous immunostimulatory lipoprotein. We investigated the specificity and molecular mechanism of this regulation, demonstrating that Cas9 controls a highly specific regulon of four genes that must be repressed for bacterial virulence. Regulation occurs through a protospacer adjacent motif (PAM)-dependent interaction of Cas9 with its endogenous DNA targets, dependent on a non-canonical small RNA (scaRNA) and tracrRNA. The limited complementarity between scaRNA and the endogenous DNA targets precludes cleavage, highlighting the evolution of scaRNA to repress transcription without lethally targeting the chromosome. We show that scaRNA can be reprogrammed to repress other genes, and with engineered, extended complementarity to an exogenous target, the repurposed scaRNA:tracrRNA-FnoCas9 machinery can also direct DNA cleavage. Natural Cas9 transcriptional interference likely represents a broad paradigm of regulatory functionality, which is potentially critical to the physiology of numerous Cas9-encoding pathogenic and commensal organisms.
    • Cell Polarization and Epigenetic Status Shape the Heterogeneous Response to Type III Interferons in Intestinal Epithelial Cells.

      Bhushal, Sudeep; Wolfsmüller, Markus; Selvakumar, Tharini A; Kemper, Lucas; Wirth, Dagmar; Hornef, Mathias W; Hauser, Hansjörg; Köster, Mario; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017)
      Type I and type III interferons (IFNs) are crucial components of the first-line antiviral host response. While specific receptors for both IFN types exist, intracellular signaling shares the same Jak-STAT pathway. Due to its receptor expression, IFN-λ responsiveness is restricted mainly to epithelial cells. Here, we display IFN-stimulated gene induction at the single cell level to comparatively analyze the activities of both IFN types in intestinal epithelial cells and mini-gut organoids. Initially, we noticed that the response to both types of IFNs at low concentrations is based on a single cell decision-making determining the total cell intrinsic antiviral activity. We identified histone deacetylase (HDAC) activity as a crucial restriction factor controlling the cell frequency of IFN-stimulated gene (ISG) induction upon IFN-λ but not IFN-β stimulation. Consistently, HDAC blockade confers antiviral activity to an elsewise non-responding subpopulation. Second, in contrast to the type I IFN system, polarization of intestinal epithelial cells strongly enhances their ability to respond to IFN-λ signaling and raises the kinetics of gene induction. Finally, we show that ISG induction in mini-gut organoids by low amounts of IFN is characterized by a scattered heterogeneous responsiveness of the epithelial cells and HDAC activity fine-tunes exclusively IFN-λ activity. This study provides a comprehensive description of the differential response to type I and type III IFNs and demonstrates that cell polarization in gut epithelial cells specifically increases IFN-λ activity.
    • Cell therapy products: focus on issues with manufacturing and quality control of chimeric antigen receptor T-cell therapies

      Eyles, Jim E; Vessillier, Sandrine; Jones, Anika; Stacey, Glyn; Schneider, Christian K; Price, Jack; TWINCORE, Zentrum für experimentelle und klinische Infektionsforschung GmbH,Feodor-Lynen Str. 7, 30625 Hannover, Germany.
      Recent accelerated approvals of Chimeric Antigen Receptor T‐cell (CAR‐T) therapies targeting refractory haematological malignancies underscore the potential for this novel technology platform to provide new therapeutic options for oncology areas with high unmet medical needs. However, these powerful ‘living drugs’ are markedly different to conventional small molecule and biologic therapies on several levels. The highly complex nature and varied composition of CAR‐T based products still requires considerable investigation to resolve the best approaches to ensure reproducible and cost‐effective manufacture, clinical development, and application. This review will focus on key issues for manufacturing and quality control of these exciting new therapeutic modalities, preceded by a brief description of CAR principals and clinical development considerations. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
    • Cell therapy products: focus on issues with manufacturing and quality control of chimeric antigen receptor T-cell therapies

      Eyles, Jim E; Vessillier, Sandrine; Jones, Anika; Stacey, Glyn; Schneider, Christian K; Price, Jack; TWINCORE, Zentrum für experimentelle und klinische Infektionsforschung GmbH,Feodor-Lynen Str. 7, 30625 Hannover, Germany. (2018-12-17)
    • Challenges in warranting access to prophylaxis and therapy for hepatitis B virus infection.

      Debarry, Jennifer; Cornberg, Markus; Manns, Michael P; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-01)
      Despite an available vaccine and efficient treatment for hepatitis B virus (HBV) infection, chronic HBV infection still remains a major global threat, and one of the top 20 causes of human mortality worldwide. One of the major challenges in controlling HBV infection is the high number of undiagnosed chronic carriers and the lack of access to prophylaxis and treatment in several parts of the world. We discuss relevant barriers that need to be overcome to achieve global control of HBV infection and make eradication possible. Most important, vaccination must be scaled-up to lower the risk of vertical transmission and decrease the number of new infections, and comprehensive screening programs must be linked to care to obtain a better rate of diagnosis and treatment. This can probably only be achieved if sustainable funding is available. We therefore emphasize the importance of making the management of viral hepatitis a global health priority.
    • Characterization and role of a metalloprotease induced by chitin in Serratia sp. KCK.

      Kim, Hyun-Soo; Golyshin, Peter N; Timmis, Kenneth N; Department of Environmental Microbiology, The Helmholtz Center for Infection Research, Braunschweig, Germany. hyun1006@korea.ac.kr (2007-11)
      A metalloprotease induced by chitin in a new chitinolytic bacterium Serratia sp. Strain KCK was purified and characterized. Compared with other Serratia enzymes, it exhibited a rather broad pH activity range (pH 5.0-8.0), and thermostability. The cognate ORF, mpr, was cloned and expressed. Its deduced amino acid sequence showed high similarity to those of bacterial zinc-binding metalloproteases and a well-conserved serralysin family motif. Pretreatment of chitin with the Mpr protein promoted chitin degradation by chitinase A, which suggests that Mpr participates in, and facilitates, chitin degradation by this microorganism.
    • Characterization of Populations by Multilocus Variable Number of Tandem Repeats (MLVA) Genotyping from Drinking Water and Biofilm in Hospitals from Different Regions of the West Bank.

      Zayed, Ashraf R; Pecellin, Marina; Salah, Alaa; Alalam, Hanna; Butmeh, Suha; Steinert, Michael; Lesnik, Rene; Brettar, Ingrid; Höfle, Manfred G; Bitar, Dina M; et al. (MDPI, 2020-10-22)
      The West Bank can be considered a high-risk area for Legionnaires' disease (LD) due to its hot climate, intermittent water supply and roof storage of drinking water. Legionella, mostly L. pneumophila, are responsible for LD, a severe, community-acquired and nosocomial pneumonia. To date, no extensive assessment of Legionella spp and L. pneumophila using cultivation in combination with molecular approaches in the West Bank has been published. Two years of environmental surveillance of Legionella in water and biofilms in the drinking water distribution systems (DWDS) of eight hospitals was carried out; 180 L. pneumophila strains were isolated, mostly from biofilms in DWDS. Most of the isolates were identified as serogroup (Sg) 1 (60%) and 6 (30%), while a minor fraction comprised Sg 8 and 10. Multilocus Variable number of tandem repeats Analysis using 13 loci (MLVA-8(12)) was applied as a high-resolution genotyping method and compared to the standard Sequence Based Typing (SBT). The isolates were genotyped in 27 MLVA-8(12) genotypes (Gt), comprising four MLVA clonal complexes (VACC 1; 2; 5; 11). The major fraction of isolates constituted Sequence Type (ST)1 and ST461. Most of the MLVA-genotypes were highly diverse and often unique. The MLVA-genotype composition showed substantial regional variability. In general, the applied MLVA-method made it possible to reproducibly genotype the isolates, and was consistent with SBT but showed a higher resolution. The advantage of the higher resolution was most evident for the subdivision of the large strain sets of ST1 and ST461; these STs were shown to be highly pneumonia-relevant in a former study. This shows that the resolution by MLVA is advantageous for back-tracking risk sites and for the avoidance of outbreaks of L. pneumophila. Overall, our results provide important insights into the detailed population structure of L. pneumophila, allowing for better risk assessment for DWDS.
    • Characterization of a transcriptional TPP riboswitch in the human pathogen Neisseriameningitidis.

      Righetti, Francesco; Materne, Solange Lise; Boss, John; Eichner, Hannes; Charpentier, Emmanuelle; Loh, Edmund; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Taylor & Francis, 2020-02-20)
      Increasing evidence has demonstrated that regulatory RNA elements such as riboswitches (RS) play a pivotal role in the fine-tuning of bacterial gene expression. In this study, we investigated and characterized a novel transcriptional thiamine pyrophosphate (TPP) RS in the obligate human pathogen N. meningitidis MC58 (serogroup B). This RS is located in the 5´ untranslated region upstream of thiC gene, encoding a protein involved in TPP biosynthesis, an essential cofactor for all living beings. Primer extension revealed the transcriptional start site of thiC. Northern blot analysis of thiC mRNA and reporter gene studies confirmed the presence of an active TPP-sensing RS. Expression patterns of the wild-type RS and site-specific mutants showed that it is an OFF switch that controls transcription elongation of thiC mRNA. Interestingly, the regulatory mechanism of the meningococcal thiC RS resembles the Gram-positive Bacillus subtilis thiC RS rather than the Gram-negative Escherichia coli thiC RS. Therefore, the meningococcal thiC RS represents a rare example of transcriptional RS in a Gram-negative bacterium. We further observed that the RS is actively involved in modulating gene expression in response to different growth media and to supplemented bacterial and eukaryotic cell lysates as possible sources of nutrients in the nasopharynx. Our results suggest that RS-mediated gene regulation could influence meningococcal fitness, through the fine-tuning of biosynthesis and scavenging of nutrients and cofactors, such as thiamine.
    • Characterization of marine isoprene-degrading communities.

      Alvarez, Laura Acuña; Exton, Daniel A; Timmis, Kenneth N; Suggett, David J; McGenity, Terry J; Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK. (2009-12)
      Isoprene is a volatile and climate-altering hydrocarbon with an atmospheric concentration similar to that of methane. It is well established that marine algae produce isoprene; however, until now there was no specific information about marine isoprene sinks. Here we demonstrate isoprene consumption in samples from temperate and tropical marine and coastal environments, and furthermore show that the most rapid degradation of isoprene coincides with the highest rates of isoprene production in estuarine sediments. Isoprene-degrading enrichment cultures, analysed by denaturing gradient gel electrophoresis and 454 pyrosequencing of the 16S rRNA gene and by culturing, were generally dominated by Actinobacteria, but included other groups such as Alphaproteobacteria and Bacteroidetes, previously not known to degrade isoprene. In contrast to specialist methane-oxidizing bacteria, cultivated isoprene degraders were nutritionally versatile, and nearly all of them were able to use n-alkanes as a source of carbon and energy. We therefore tested and showed that the ubiquitous marine hydrocarbon-degrader, Alcanivorax borkumensis, could also degrade isoprene. A mixture of the isolates consumed isoprene emitted from algal cultures, confirming that isoprene can be metabolized at low, environmentally relevant concentrations, and suggesting that, in the absence of spilled petroleum hydrocarbons, algal production of isoprene could maintain viable populations of hydrocarbon-degrading microbes. This discovery of a missing marine sink for isoprene is the first step in obtaining more robust predictions of its flux, and suggests that algal-derived isoprene provides an additional source of carbon for diverse microbes in the oceans.