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  • 1
    Electronic Resource
    Electronic Resource
    Monitoring trichloroethylene mineralization by Pseudomonas cepacia G4 PR1 (1995)
    Springer
    Applied microbiology and biotechnology 44 (1995), S. 259-264 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract To analyze the extent of mineralization of trichloroethylene (TCE) without disturbing an actively growing biofilm, a minimal growth medium was formulated that reduces the concentration of chloride ions to the extent that the chloride ions generated from TCE mineralization may be detected with a chloride-ion-specific electrode. By substituting chloride salts with phosphates and nitrates, a chloride-free minimal medium was produced that yields a specific growth rate for Pseudomonas cepacia G4 PR1 which was 93% of that in chloride-ion-containing minimal medium. Furthermore, TCE degradation by resting cell suspensions was similar in both media (85% of 75 μM TCE degraded in 6 h), and complete mineralization of TCE was slightly superior in the chloride-free minimal medium (77% compared to 60% of 75 μM TCE mineralized in 6 h). In addition, indole-containing, minimal-medium agar plates were developed to indicate the presence of the TCE-degrading enzyme toluene ortho-monooxygenase (fire-engine-red colonies) as well as to distinguish this enzyme from other TCE-degrading enzymes (toluene dioxygenase and toluene para-monooxygenase).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164512
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  • 2
    Electronic Resource
    Electronic Resource
    Corrosion inhibition by aerobic biofilms on SAE 1018 steel (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 62-68 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Carbon steel (SAE 1018) samples were exposed to complex liquid media containing either the aerobic bacterium Pseudomonas fragi or the facultative anaerobe Escherichia coli DH5α. Compared to sterile controls, mass loss was consistently 2- to 10-fold lower in the presence of these bacteria which produce a protective biofilm. Increasing the temperature from 23 °C to 30 °C resulted in a 2- to 5-fold decrease in corrosion inhibition with P. fragi whereas the same shift in temperature resulted in a 2-fold increase in corrosion inhibition with E. coli DH5α. Corrosion observed with non-biofilm-forming Streptomyces lividans TK24 was similar to that observed in sterile media. A dead biofilm, generated in situ by adding kanamycin to an established biofilm, did not protect the metal (corrosion rates were comparable to those in the sterile control), and mass loss in cell-free, spent Luria-Bertani (LB) medium was similar to that in sterile medium. Confocal laser scanning microscopy analysis confirmed the presence of a biofilm consisting of live and dead cells embedded in a sparse glycocalyx matrix. Mass-loss measurements were consistent with microscopic observations of the metal surface after 2 weeks of exposure, indicating that uniform corrosion occurred. The biofilm was also able to withstand mild agitation (60 rpm), provided that sufficient time was given for its development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050889
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  • 3
    Electronic Resource
    Electronic Resource
    Degradation of 2,4,5-trichlorophenol and 2,3,5,6-tetrachlorophenol by combining pulse electric discharge with bioremediation (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 261-266 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Degradation of 2,4,5-trichlorophenol (2,4,5-TCP) and 2,3,5,6-tetrachlorophenol (TeCP) was studied using a two-stage approach that utilized efficient pulse electric discharge (PED) followed by biological degradation with a consortium from acclimated return activated sludge. The chlorinated phenols were treated in the PED reactor as an aerosol at a voltage of 55–60 kV, a frequency of 385 Hz, a current of 50–60, and with a 200-ns pulse. As determined by gas chromatography and mass spectrometry (GC/MS), the first stage converted 500 ppm 2,4,5-TCP to 163 ppm 2,4,5-TCP and dimethyldecene, dichloronaphthalenol, octyl acetate, and silyl esters. The total carbon content of 2,4,5-TCP after PED treatment was determined to be 228 ± 35 ppm. The remaining 2,4,5-TCP and the products formed were then mineralized by the acclimated activated sludge in shake flasks; the initial rate of degradation of 2,4,5-TCP was calculated to be 5 nmol min−1 mg protein−1 at 163 ppm initial concentration (three orders of magnitude higher than the only rate found in the literature). By combining the two techniques, a synergistic effect (2.3-fold increase in the concentration of 2,4,5-TCP degraded and 3.3-fold increase in total carbon degraded) was observed, in that bacteria without any treatment degraded a maximum of 70 ppm 2,4,5-TCP but after PED treatment 163 ppm 2,4,5-TCP was degraded. TeCP was also mineralized by the acclimated activated sludge after treatment with PED. This two-stage approach was also evaluated using a continuous 1-l fluidized-bed reactor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051519
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  • 4
    Electronic Resource
    Electronic Resource
    Axenic aerobic biofilms inhibit corrosion of copper and aluminum (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 787-790 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The corrosion behavior of unalloyed copper and aluminum alloy 2024 in modified Baar's medium has been studied with continuous reactors using electrochemical impedance spectroscopy. An axenic aerobic biofilm of either Pseudomonas fragi K or Bacillus brevis 18 was able to lessen corrosion as evidenced by a consistent 20-fold increase in the low-frequency impedance value of copper as well as by a consistent four- to seven-fold increase in the polarization resistance of aluminum 2024 after six days exposure compared to sterile controls. This is the first report of axenic aerobic biofilms inhibiting generalized corrosion of copper and aluminum. Addition of the representative sulfate-reducing bacterium (SRB) Desulfovibrio vulgaris (to simulate consortia corrosion behavior) to either the P. fragi K or B. brevis 18 protective biofilm on copper increased the corrosion to that of the sterile control unless antibiotic (ampicillin) was added to inhibit the growth of SRB in the biofilm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051592
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  • 5
    Electronic Resource
    Electronic Resource
    Trichloroethylene degradation and mineralization by pseudomonads and Methylosinus trichosporium OB3b (1996)
    Springer
    Applied microbiology and biotechnology 45 (1996), S. 248-256 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  To examine the trichloroethylene (C2HCl3)-degrading capability of five microorganisms, the maximum rate, extent, and degree of C2HCl3 mineralization were evaluated for Pseudomonas cepacia G4, Pseudomonas cepacia G4 PR1, Pseudomonas mendocina KR1, Pseudomonas putida F1, and Methylosinus trichosporium OB3b using growth conditions commonly reported in the literature for expression of oxygenases responsible for C2HCl3 degradation. By varying the C2HCl3 concentration from 5 μM to 75 μM, V max and K m values for C2HCl3 degradation were calculated as 9 nmol/(min mg protein) and 4 μM for P. cepacia G4, 18 nmol/(min mg protein) and 29 μM for P. cepacia G4 PR1, 20 nmol/(min mg protein) and 10 μM for P. mendocina KR1, and 8 nmol/(min mg protein) and 5 μM for P. putida F1. This is the first report of these Michaelis-Menten parameters for P. mendocina KR1, P. putida F1, and P. cepacia G4 PR1. At 75 μM, the extent of C2HCl3 that was degraded after 6 h of incubation with resting cells was 61%–98%; the highest degradation being achieved by toluene-induced P. mendocina KR1. The extent of C2HCl3 mineralization in 6 h (as indicated by concentration of chloride ion) was also measured and varied from 36% for toluene-induced P. putida F1 to 102% for M. trichosporium OB3b. Since C2HCl3 degradation requires new bio-mass, the specific growth rate (μmax) of each of the C2HCl3-degradation microorganisms was determined and varied from 0.080/h (M. trichosporium OB3b) to 0.864/h (P. cepacia G4 PR1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050679
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  • 6
    Electronic Resource
    Electronic Resource
    Metal ions and chloramphenicol inhibition of soluble methane monooxygenase from Methylosinus trichosporium OB3b (1996)
    Springer
    Applied microbiology and biotechnology 45 (1996), S. 744-749 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Transcription of soluble methane monooxygenase (sMMO) of methanotrophs is tightly regulated by low concentrations of copper ions [Cu(II); e.g., transcription is completely repressed at copper concentrations higher than 0.86 μmol/g dry cell weight]. In addition to this genetic-level regulation, copper ions have been shown to inhibit the in vitro activity of sMMO from the type X methanotroph Methylococcus capsulatus (Bath) by inactivating only the reductase component of this enzyme (Green et al. 1985). In this study, in vitro sMMO inhibition by 12 metal ions and 10 medium ingredients was investigated for the first time using sMMO purified from the type II methanotroph Methylosinus trichosporium OB3b. Cu(I) and Cu(II) decreased sMMO activity of Methylosinus trichosporium OB3b by inhibiting not only the reductase but the hydroxylase component as well. Ni(II) also inhibited both enzyme components, but the inhibition was weaker than with copper ions. Zn(II) inhibited sMMO by lowering the activity of the hydroxylase only. Other transition metals such as Co(II), Mn(II), Fe(II) and Fe(III) did not show considerable impact on sMMO activity. The inhibition mechanisms were not determined, but Ni(II) and Zn(II) aggregated the reductase component of sMMO, and Zn(II) also precipitated the hydroxylase component. Cu(II) caused the reductase to precipitate, but Cu(I) did not aggregate either sMMO component. The aggregated proteins could not be dissolved in the solution of ethylenediaminetetraacetic acid disodium salt. Little or no sMMO inhibition was observed with various medium components examined including glucose, methanol, ethanol, dimethyl sulfone, ammonium chloride, methylamine (at a 500 molar ratio of medium component to the hydroxylase), kanamycin, and isopropylthiogalactopyranoside (at a molar ratio of 50); however, chloramphenicol inhibited sMMO at a molar ratio of 50.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050757
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  • 7
    Electronic Resource
    Electronic Resource
    Axenic aerobic biofilms inhibit corrosion of SAE 1018 steel through oxygen depletion (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 11-17 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Corrosion inhibition of SAE 1018 steel by pure-culture biofilms of Pseudomonas fragi and Escheri-chia coli DH5α has been evaluated in complex Luria-Bertani medium, seawater-mimicking medium, and modified Baar's medium at 30 °C. In batch cultures, both bacteria inhibited corrosion three to six fold compared to sterile controls, and the corrosion was comparable to that observed in anaerobic sterile media. To corroborate this result, a continuous reactor and electrochemical impedance spectroscopy were used to show that both P. fragi K and E. coli DH5α decreased the corrosion rate by 4- to 40-fold as compared to sterile controls; this matched the decrease in corrosion found with sterile medium in the absence of oxygen and with E. coli DH5α grown anaerobically. In addition, the requirement for live respiring cells was demonstrated by the increase in the corrosion rate that was observed upon killing the P. fragi K biofilm in continuous cultures, and it was shown that fermentation products do not cause an increase in corrosion. Hence, pure-culture biofilms inhibit corrosion of SAE 1018 steel by depleting oxygen at the metal surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051007
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  • 8
    Electronic Resource
    Electronic Resource
    Creating auxotrophic mutants in Methylophilus methylotrophus AS1 by combining electroporation and chemical mutagenesis (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 105-108 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Stable auxotrophic mutants of the methylotroph Methylophilus methylotrophus AS1 were obtained by a novel mutagenesis technique in which electroporation is used to transport the chemical mutagen N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) across the cell membrane. By combining chemical mutagenesis with electroporation and screening single colonies for auxotrophy in 36 different amino acids and growth factors, 3 auxotrophs per 156 colonies screened were obtained, whereas no auxotrophs were found with chemical mutagenesis alone. MNNG mutagen toxicity was also increased in the methylotroph with this novel mutagenesis technique (death rate 96% compared to 79%). This technique did not increase the mutation rate for strain Escherichia coli BK6 which responds well to simple exposure to the mutagen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051023
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  • 9
    Electronic Resource
    Electronic Resource
    Inhibiting sulfate-reducing bacteria in biofilms on steel with antimicrobial peptides generated in situ (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 267-275 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In batch and continuous fermentations, the reduction in corrosion of SAE 1018 mild steel and 304 stainless steel caused by inhibition of the reference sulfate-reducing bacterium (SRB) Desulfovibrio vulgaris by a protective, antimicrobial-producing Bacillus brevis biofilm was investigated. The presence of D. vulgaris produced a thick black precipitate on mild steel and a higher corrosion rate in batch cultures than that seen in a mono-culture of non-antimicrobial-producing Pseudomonas fragi K upon the addition of SRB to the aerobic P. fragi K biofilm. In continuous reactors, the polarization resistance R p decreased for stainless steel and increased for mild steel upon the addition of SRB to a P. fragi K biofilm. Addition of either 200 μg/ml ampicillin, chloramphenicol, or ammonium molybdate to batch and continuous reactors after SRB had colonized the metal was ineffective in killing SRB, as inferred from the lack of change in both R p and the impedance spectra. However, when ampicillin was added prior to SRB colonization, the growth of SRB was completely inhibited on stainless steel in continuous reactors. Prior addition of ampicillin was only able to delay the growth of SRB on mild steel in continuous reactors. External addition of the purified peptide antimicrobial agent gramicidin S prior to the addition of SRB also inhibited the growth of SRB on stainless steel in continuous reactors, and the SRB were also inhibited on stainless steel in both batch and continuous reactors by producing gramicidin S in situ in a protective biofilm when the gramicidin-S-overproducing strain Bacillus brevis 18 was used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051520
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  • 10
    Electronic Resource
    Electronic Resource
    Monitoring trichloroethylene mineralization by Pseudomonas cepacia G4 PR1 (1995)
    Springer
    Applied microbiology and biotechnology 44 (1995), S. 259-264 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract To analyze the extent of mineralization of trichloroethylene (TCE) without disturbing an actively growing biofilm, a minimal growth medium was formulated that reduces the concentration of chloride ions to the extent that the chloride ions generated from TCE mineralization may be detected with a chloride-ion-specific electrode. By substituting chloride salts with phosphates and nitrates, a chloride-free minimal medium was produced that yields a specific growth rate for Pseudomonas cepacia G4 PR1 which was 93% of that in chloride-ion-containing minimal medium. Furthermore, TCE degradation by resting cell suspensions was similar in both media (85% of 75 μM TCE degraded in 6 h), and complete mineralization of TCE was slightly superior in the chloride-free minimal medium (77% compared to 60% of 75 μM TCE mineralized in 6 h). In addition, indole-containing, minimal-medium agar plates were developed to indicate the presence of the TCE-degrading enzyme toluene ortho-monooxygenase (fire-engine-red colonies) as well as to distinguish this enzyme from other TCE-degrading enzymes (toluene dioxygenase and toluene para-monooxygenase).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050551
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