Journal: Applied and Environmental Microbiology

Abbreviation

Appl. Environ. Microbiol

Publisher

American Society for Microbiology

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ISSN

0099-2240
1098-5336

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Publications1 - 10 of 162
  • Predominance of nonculturable cells of the biocontrol strain Pseudomonas fluorescens CHA0 in the surface horizon of large outdoor lysimeters
    Item type: Journal Article
    Troxler, Josef; Zala, Marcello; Moënne-Loccoz, Yvan; et al. (1997)
    Applied and Environmental Microbiology
  • Heterologous production of antimicrobial peptides in Propionibacterium freudenreichii
    Item type: Journal Article
    Brede, Dag Anders; Faye, Therese; Stierli, Melanie Patricia; et al. (2005)
    Applied and Environmental Microbiology
    Heterologous bacteriocin production in Propionibacterium freudenreichii is described. We developed an efficient system for DNA shuttling between Escherichia coli and P. freudenreichii using vector pAMT1. It is based on the P. freudenreichii rolling-circle replicating plasmid pLME108 and carries the cml (A)/cmx(A) chloramphenicol resistance marker. Introduction of the propionicin T1 structural gene (pctA) into pAMT1 under the control of the constitutive promoter (P₄) yielded bacteriocin in amounts equal to those of the wild-type producer Propionibacterium thoenii 419. The P. freudenreichii clone showed propionicin T1 activity in coculture, killing 90% of sensitive bacteria within 48 h. The pamA gene from P. thoenii 419 encoding the protease-activated antimicrobial peptide (PAMP) was cloned and expressed in P. freudenreichii , resulting in secretion of the pro-PAMP protein. Like in the wild type, PAMP activation was dependent on externally added protease. Secretion of the antimicrobial peptide was obtained from a clone in which the pamA signal peptide and PAMP were fused in frame. The promoter region of pamA was identified by fusion of putative promoter fragments to the coding sequence of the pctA gene. The P₄ and Pₚₐₘₚ promoters directed constitutive gene expression, and activity of both promoters was enhanced by elements upstream of the promoter core region.
  • Molecular basis for anaerobic growth of Saccharomyces cerevisiae on xylose, investigated by global gene expression and metabolic flux analysis
    Item type: Journal Article
    Sonderegger, Marco; Jeppson, Marie; Hahn-Hägerdal, Bärbel; et al. (2004)
    Applied and Environmental Microbiology
    Yeast xylose metabolism is generally considered to be restricted to respirative conditions because the two-step oxidoreductase reactions from xylose to xylulose impose an anaerobic redox imbalance. We have recently developed, however, a Saccharomyces cerevisiae strain that is at present the only known yeast capable of anaerobic growth on xylose alone. Using transcriptome analysis of aerobic chemostat cultures grown on xylose-glucose mixtures and xylose alone, as well as a combination of global gene expression and metabolic flux analysis of anaerobic chemostat cultures grown on xylose-glucose mixtures, we identified the distinguishing characteristics of this unique phenotype. First, the transcript levels and metabolic fluxes throughout central carbon metabolism were significantly higher than those in the parent strain, and they were most pronounced in the xylose-specific, pentose phosphate, and glycerol pathways. Second, differential expression of many genes involved in redox metabolism indicates that increased cytosolic NADPH formation and NADH consumption enable a higher flux through the two-step oxidoreductase reaction of xylose to xylulose in the mutant. Redox balancing is apparently still a problem in this strain, since anaerobic growth on xylose could be improved further by providing acetoin as an external NADH sink. This improved growth was accompanied by an increased ATP production rate and was not accompanied by higher rates of xylose uptake or cytosolic NADPH production. We concluded that anaerobic growth of the yeast on xylose is ultimately limited by the rate of ATP production and not by the redox balance per se, although the redox imbalance, in turn, limits ATP production.
  • Suitability of Quantitative Real-Time PCR To Estimate the Biomass of Fungal Root Endophytes
    Item type: Journal Article
    Tellenbach, Christoph; Gruenig, Christoph R.; Sieber, Thomas Niklaus (2010)
    Applied and Environmental Microbiology
    A nested single-copy locus-based quantitative PCR (qPCR) assay and a multicopy locus-based qPCR assay were developed to estimate endophytic biomass of fungal root symbionts belonging to the Phialocephala fortinii sensu lato-Acephala applanata species complex (PAC). Both assays were suitable for estimation of endophytic biomass, but the nested assay was more sensitive and specific for PAC. For mycelia grown in liquid cultures, the correlation between dry weight and DNA amount was strong and statistically significant for all three examined strains, allowing accurate prediction of fungal biomass by qPCR. For mycelia colonizing cellophane or Norway spruce roots, correlation between biomass estimated by qPCR and microscopy was strain dependent and was affected by the abundance of microsclerotia. Fungal biomass estimated by qPCR and microscopy correlated well for one strain with poor microsclerotia formation but not for two strains with high microsclerotia formation. The accuracy of qPCR measurement is constrained by the variability of cell volumes, while the accuracy of microscopy can be hampered by overlapping fungal structures and lack of specificity for PAC. Nevertheless, qPCR is preferable because it is highly specific for PAC and less time-consuming than quantification by microscopy. There is currently no better method than qPCR-based quantification using calibration curves obtained from pure mycelia to predict PAC biomass in substrates. In this study, the DNA amount of A. applanata extracted from 15 mm of Norway spruce fine root segments (mean diameter, 610 μm) varied between 0.3 and 45.5 ng, which corresponds to a PAC biomass of 5.1 ± 4.5 μg (estimate ± 95% prediction interval) and 418 ± 264 μg.
  • Association of biodiversity with the rates of micropollutant biotransformations among full-scale wastewater treatment plant communities
    Item type: Journal Article
    Johnson, David R.; Helbling, Damian E.; Lee, Tae K.; et al. (2015)
    Applied and Environmental Microbiology
    Biodiversities can differ substantially among different wastewater treatment plant (WWTP) communities. Whether differences in biodiversity translate into differences in the provision of particular ecosystem services, however, is under active debate. Theoretical considerations predict that WWTP communities with more biodiversity are more likely to contain strains that have positive effects on the rates of particular ecosystem functions, thus resulting in positive associations between those two variables. However, if WWTP communities were sufficiently biodiverse to nearly saturate the set of possible positive effects, then positive associations would not occur between biodiversity and the rates of particular ecosystem functions. To test these expectations, we measured the taxonomic biodiversity, functional biodiversity, and rates of 10 different micropollutant biotransformations for 10 full-scale WWTP communities. We have demonstrated that biodiversity is positively associated with the rates of specific, but not all, micropollutant biotransformations. Thus, one cannot assume whether or how biodiversity will associate with the rate of any particular micropollutant biotransformation. We have further demonstrated that the strongest positive association is between biodiversity and the collective rate of multiple micropollutant biotransformations. Thus, more biodiversity is likely required to maximize the collective rates of multiple micropollutant biotransformations than is required to maximize the rate of any individual micropollutant biotransformation. We finally provide evidence that the positive associations are stronger for rare micropollutant biotransformations than for common micropollutant biotransformations. Together, our results are consistent with the hypothesis that differences in biodiversity can indeed translate into differences in the provision of particular ecosystem services by full-scale WWTP communities.
  • Comparison of ATPase-encoding type III secretion system hrcN genes in biocontrol fluorescent pseudomonads and in phytopathogenic proteobacteria
    Item type: Journal Article
    Rezzonico, Fabio; Défago, Geneviève; Moënne-Loccoz, Yvan (2004)
    Applied and Environmental Microbiology
  • Field-Scale Transplantation Experiment To Investigate Structures of Soil Bacterial Communities at Pioneering Sites
    Item type: Journal Article
    Lazzaro, Anna; Gauer, Andreas; Zeyer, Josef (2011)
    Applied and Environmental Microbiology
  • Widespread Distribution of Poribacteria in Demospongiae
    Item type: Journal Article
    Lafi, Feras F.; Fuerst, John A.; Fieseler, Lars; et al. (2009)
    Applied and Environmental Microbiology
    Poribacteria were found in nine sponge species belonging to six orders of Porifera from three oceans. Phylogenetic analysis revealed four distinct poribacterial clades, which contained organisms obtained from several different geographic regions, indicating that the distribution of poribacteria is cosmopolitan. Members of divergent poribacterial clades were also found in the same sponge species in three different sponge genera.
  • Effects of Root-Colonizing Fluorescent Pseudomonas Strains on Arabidopsis Resistance to a Pathogen and an Herbivore
    Item type: Journal Article
    Löser, Tobias B.; Mescher, Mark C.; De Moraes, Consuelo M.; et al. (2021)
    Applied and Environmental Microbiology
    Rhizobacteria in the genus Pseudomonas can enhance plant resistance to a range of pathogens and herbivores. However, resistance to these different classes of plant antagonists is mediated by different molecular mechanisms, and the extent to which induced systemic resistance by Pseudomonas can simultaneously protect plants against both pathogens and herbivores remains unclear. We screened 12 root-colonizing Pseudomonas strains to assess their ability to induce resistance in Arabidopsis thaliana against a foliar pathogen (Pseudomonas syringae DC3000) and a chewing herbivore (Spodoptera littoralis). None of our 12 strains increased plant resistance against herbivory; however, four strains enhanced pathogen resistance, and one of these (Pseudomonas strain P97-38) also made plants more susceptible to herbivory. Phytohormone analyses revealed stronger salicylic acid induction in plants colonized by P97-38 (versus controls) following subsequent pathogen infection but weaker induction of jasmonic acid (JA)-mediated defenses following herbivory. We found no effects of P97-38 inoculation on herbivore-relevant nutrients such as sugars and protein, suggesting that the observed enhancement of susceptibility to S. littoralis is due to effects on plant defense chemistry rather than nutrition. These findings suggest that Pseudomonas strains that enhance plant resistance to pathogens may have neutral or negative effects on resistance to herbivores and provide insight into potential mechanisms associated with effects on different classes of plant antagonists. Improved understanding of these effects has potentially important implications for the use of rhizobacteria inoculation in agriculture.
  • Benthic bacterial and fungal productivity and carbon turnover in a freshwater marsh
    Item type: Journal Article
    Buesing, Nanna; Gessner, Mark O. (2006)
    Applied and Environmental Microbiology
Publications1 - 10 of 162