Papers by Kjeld Ingvorsen
Applied and Environmental Microbiology, May 1, 1998
Applied Microbiology and Biotechnology, Nov 3, 1999
An extremely halotolerant mannan-degrading bacterium (strain NN) was isolated from the Great Salt... more An extremely halotolerant mannan-degrading bacterium (strain NN) was isolated from the Great Salt Lake, Utah, USA. Strain NN grew at salinities from 0 to 20% NaCl with optimal growth at 0% NaCl. When grown on 0.2% (w/v) locust bean gum as the carbon source at 10% NaCl, both b-mannanase and b-mannosidase activities were produced. b-Mannosidase activity was shown to be cell-associated, while at least 23% of the total b-mannanase activity was extracellular. The optimum temperature and pH for b-mannanase activity were 70°C and 7.6, and for b-mannosidase 25°C and 7.0. The b-mannanase system retained full activity after 24 h of incubation at 60°C and 10% NaCl. b-Mannanase activity was maximal at 1% NaCl and b-mannosidase activity at 0.5% NaCl. Despite these low salinity optima, 50% and 100% respectively of the initial b-mannanase and b-mannosidase activities remained after 48 h of incubation at 20% NaCl, indicating a high degree of halostability. Sodium dodecyl sulphate/polyacrylamide gel electrophoresis revealed the presence of at least eight dierent mannan-degrading proteins in the cell-free culture supernatant of cultures grown on locust bean gum.
FEMS Microbiology Ecology, Jan 17, 2006
Limnology and Oceanography, Mar 1, 1979
A method is described for chemical determination of oxygen and sulfide in the same water sample. ... more A method is described for chemical determination of oxygen and sulfide in the same water sample. Sulfide is first separated by precipitation with zinc hydroxide, oxygen then determined by the Winkler technique in the clear supernatant. The mutual interference between the oxygen and the sulfide determinations is <l-2%. The method has proven useful for field applications: as an example, the diurnal variation in oxygen and sulfide of a shallow lagoon is presented.
Applied and Environmental Microbiology, Nov 15, 2009
Novartis Foundation Symposium, Sep 28, 2007
Nitrile-hydrating enzymes produced by bacteria and fungi catalyse the conversion of a large numbe... more Nitrile-hydrating enzymes produced by bacteria and fungi catalyse the conversion of a large number of chemically diverse nitriles, including many economically important compounds used industrially for chemical synthesis of amides and acids. This paper presents data on two new, highly different nitrile-hydrolysing enzymes which were isolated in connection with our studies on enzymic nitrile transformations. Particular attention was paid to the enzymes&#39; substrate specificities and sensitivity to substrate/product inhibition. One of our microbial isolates was a Rhodococcus sp. (strain CH5). This strain produces a constitutive hydratase that has a broad substrate spectrum, including aliphatic and aromatic nitriles, mononitriles and dinitriles, hydroxynitriles and amino-nitriles. It also produces a constitutive amidase of equally low substrate specificity. The hydratase/amidase system catalysed the hydrolysis of D,L-aminonitriles into racemic mixtures of amino acids. Strain CH5 is able to produce high concentrations of malonic acid monoamide from malononitrile and malonamide. The other isolate, Alcaligenes sp. (strain I4), can convert high concentrations of cyanoacetate into malonic acid, presumably by means of an aliphatic nitrilase that is specific for cyanoacetate. Enzyme kinetic experiments have shown that this enzyme is very resistant to both substrate and product inhibition.
International Journal of Systematic and Evolutionary Microbiology, Sep 1, 2006
A novel moderately halophilic, sulfate-reducing bacterium, strain EtOH3 T , was isolated from ano... more A novel moderately halophilic, sulfate-reducing bacterium, strain EtOH3 T , was isolated from anoxic hypersaline (270 g NaCl l "1) sediment of the northern arm of the Great Salt Lake, Utah, USA. Cells of strain EtOH3 T were oval to rod-shaped, non-motile, non-sporulating and stained Gram-negative. The strain required sodium and magnesium ions for growth and grew at salinities of up to 240 g NaCl l "1 and 121 g MgCl 2 .6H 2 O l "1. The optimum NaCl concentration was 80-100 g l "1. Strain EtOH3 T grew at temperatures ranging from 15 to 44 6C (optimum 37 6C). The pH range for growth was 6?5-8?3 (optimum around pH 6?8). Only sulfate and thiosulfate served as electron acceptors for a broad range of electron donors including various short-chain fatty acids and primary (C 1-5) alcohols, amino acids, H 2 /acetate and H 2 /yeast extract. The G+C content of the genomic DNA was 51?4 mol%. Phylogenetic analysis of dsrAB [genes encoding the major subunits of dissimilatory (bi)sulfite reductase] and 16S rRNA gene sequence data placed strain EtOH3 T within the deltaproteobacterial family Desulfohalobiaceae. Strain EtOH3 T shared 76 and 91 % dsrAB and 16S rRNA gene sequence similarity, respectively, with the type strain of the phylogenetically most closely related species with a validly published name, Desulfohalobium retbaense DSM 5692 T. High 16S rRNA gene sequence similarity (~97 %) was shared with the recently described strain 'Desulfovermiculus halophilus' VKM B-2364. Strain EtOH3 T , however, clearly differed from this strain in both genomic G+C content and in several of its phenotypic properties. On the basis of phenotypic and genotypic characteristics, the novel species Desulfohalobium utahense sp. nov. is proposed, with strain EtOH3 T (=VKM B-2384 T =DSM 17720 T) as the type strain. Abbreviation: SRB, sulfate-reducing bacteria. The GenBank/EMBL/DDBJ accession number for the dsrAB and the 16S rRNA gene sequences of strain EtOH3 T are DQ386236 and DQ067421, respectively. A transmission electron micrograph of a cell of strain EtOH3 T is available as supplementary material in IJSEM Online.
Bergey's Manual of Systematics of Archaea and Bacteria, Sep 14, 2015
Archives of Microbiology, May 6, 2016
International Journal of Systematic and Evolutionary Microbiology, May 1, 2006
A novel alkalitolerant, sulphate-reducing bacterium (strain RT2 T) was isolated from alkaline dis... more A novel alkalitolerant, sulphate-reducing bacterium (strain RT2 T) was isolated from alkaline district heating water. Strain RT2 T was a motile vibrio (0?5-0?8 mm wide and 1?4-1?9 mm long) and grew at pH 6?9-9?9 (optimum at pH 9?0-9?4) and at 16-47 6C (optimum at 43 6C). The genomic DNA G+C content was 64?7 mol%. A limited number of compounds were used as electron donors with sulphate as electron acceptor, including lactate, pyruvate, formate and hydrogen/acetate. Sulphite and thiosulphate also served as electron acceptors. Based on physiological and genotypic properties, the isolate was considered to represent a novel species of the genus Desulfovibrio, for which the name Desulfovibrio alkalitolerans sp. nov. is proposed. The type strain is RT2 T (=DSM 16529 T =JCM 12612 T). The strain is the first alkali-tolerant member of the genus Desulfovibrio to be described.
Anaerobe, Dec 1, 2005
A new mesophilic sulphate-reducing bacterium, designated strain DvO5 T (T ¼ type strain), was iso... more A new mesophilic sulphate-reducing bacterium, designated strain DvO5 T (T ¼ type strain), was isolated from the outermost sulphate reduction-positive most-probable-number tube (10 À6 dilution) of an activated sludge sample, which had been oxygenated at 100% air saturation for 120 h. The motile, Gram-negative, curved 1 by 2-5 mm and non-spore-forming cells of strain DvO5 T existed singly or in chains. Strain DvO5 T grew optimally at 29 1C, pH 6.9 and 0.05% (w/v) NaCl in a medium containing lactate, sulphate and yeast extract. Sulphite, thiosulphate and elemental sulphur also served as electron acceptors whereas nitrate, nitrite or ferric iron were not reduced. Lactate, pyruvate, H 2 (with acetate as carbon source), ethanol and glycerol efficiently supported growth as electron donors. Pyruvate and malate were fermented. Strain DvO5 T reduced oxygen by oxidising endogenous polyglucose at rates ranging from 0.4 to 6.0 nmol O 2 /mg protein min depending on the oxygen concentration, the highest rates being observed at atmospheric oxygen saturation. The G+C content of the DNA was 57.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain DvO5 T was a member of the genus Desulfovibrio with D. magneticus (98.2% 16S rRNA gene sequence similarity) and D. burkinensis (97.5% 16S rRNA gene sequence similarity) being its closest relatives among validly described species. A similar phylogenetic affiliation was obtained by sequence analyses of the genes encoding the alpha and the beta subunit of dissimilatory sulphite reductase (dsrAB) as well as the alpha subunit of adenosine-5 0-phosphosulphate reductase (apsA) of strain DvO5 T. On the basis of genotypic and phenotypic characteristics, strain DvO5 T (DSM 16695 T , JCM 12613 T) is proposed as the type strain of a new species, Desulfovibrio aerotolerans sp. nov.
Extremophiles, Apr 1, 2003
The extremely halophilic archaeon, Halorhabdus utahensis, isolated from the Great Salt Lake, Utah... more The extremely halophilic archaeon, Halorhabdus utahensis, isolated from the Great Salt Lake, Utah, produced beta-xylanase and beta-xylosidase activities. Both enzymes were active over a broad NaCl range from near zero to 30% NaCl when tested with culture broth. A broad NaCl optimum was observed for beta-xylanase activity between 5% and 15% NaCl, while beta-xylosidase activity was highest at 5% NaCl. Almost half of the maximum activities remained at 27%-30% NaCl for both enzyme activities. When dialyzed culture supernatant and culture broth were employed for determination of beta-xylanase and beta-xylosidase stabilities, approximately 55% and 83% of the initial beta-xylanase and beta-xylosidase activities, respectively, remained after 24 h incubation at 20% NaCl. The enzymes were also shown to be slightly thermophilic; beta-xylanase activity exhibiting two optima at 55 degrees and 70 degrees C, while beta-xylosidase activity was optimal at 65 degrees C. SDS-PAGE and zymogram techniques revealed the presence of two xylan-degrading proteins of approximately 45 and 67 kDa in culture supernatants. To our knowledge, this paper is the first report on hemicellulose-degrading enzymes produced by an extremely halophilic archaeon.
Applied and Environmental Microbiology, Dec 1, 1981
Bacterial sulfate reduction in the surface sediment and the water column of Lake Mendota, Madison... more Bacterial sulfate reduction in the surface sediment and the water column of Lake Mendota, Madison, Wis., was studied by using radioactive sulfate ('SO42-). High rates of sulfate reduction were observed at the sediment surface, where the sulfate pool (0.2 mM S042-) had a turnover time of 10 to 24 h. Daily sulfate reduction rates in Lake Mendota sediment varied from 50 to 600 nmol of S042cm-3, depending on temperature and sampling date. Rates of sulfate reduction in the water column were 103 times lower than that for the surface sediment and, on an areal basis, accounted for less than 18% of the total sulfate reduction in the hypolimnion during summer stratification. Rates of bacterial sulfate reduction in the sediment were not sulfate limited at sulfate concentrations greater than 0.1 mM in short-term experiments. Although sulfate reduction seemed to be sulfate limited below 0.1 mM, Michaelis-Menten kinetics were not observed. The optimum temperature (36 to 3700) for sulfate reduction in the sediment was considerably higher than in situ temperatures (1 to 1300). The response of sulfate reduction to the addition of various electron donors metabolized by sulfatereducing bacteria in pure culture was investigated. The degree of stimulation was in this order: H2 > n-butanol > n-propanol > ethanol > glucose. Acetate and lactate caused no stimulation.
FEMS Microbiology Ecology, Jul 1, 2005
The present study addresses the effects of oxygen exposure on the aerobic and anaerobic respirato... more The present study addresses the effects of oxygen exposure on the aerobic and anaerobic respiratory activity of Desulfovibrio desulfuricans strain DvO1. This strain was isolated from the highest sulfate-reduction positive most-probable-number dilution (10 6) of an activated sludge sample, which had been subjected to 120 h of continuous aeration. Washed cell suspensions of strain DvO1 were aerated at 50% atmospheric oxygen saturation in sulfide-free media for a period of 33 h in the presence or absence of an external electron donor (10 mM lactate). During the aeration periods, samples were removed at intervals for determination of anaerobic INT [2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride]-reducing activity, anaerobic sulfate-reducing activity, and oxygen-reducing activity. The cell suspension aerated in the absence of lactate showed negligible endogenous oxygen reduction rates and therefore did not consume oxygen during the aeration period. In contrast, the cell suspension aerated in the presence of lactate sustained significant rates of oxygen reduction during the entire 33 h aeration period. Despite this, no explicit differences in the potential INT-, oxygen-, or sulfate-reducing activities were evident between the two cell suspensions during the aeration periods. Strain DvO1 remained viable throughout the 33 h aeration periods irrespective of the presence or absence of lactate, however, the oxygen exposure resulted in a dose-dependent reversible metabolic inactivation. Notably, lactate-dependent anaerobic sulfate-reducing activity recovered quickly upon anaerobiosis, and was more oxygen tolerant than lactate-dependent oxygen-reducing activity.
International Journal of Systematic and Evolutionary Microbiology, May 1, 2010
A novel halophilic Gram-negative sulfate-reducing bacterium affiliated with the deltaproteobacter... more A novel halophilic Gram-negative sulfate-reducing bacterium affiliated with the deltaproteobacterial family Desulfobacteraceae, strain PropA T , was isolated from the extreme hypersaline sediment of the northern arm of Great Salt Lake, Utah, USA. Comparative 16S rRNA gene sequence analysis showed that strain PropA T is the first cultured representative of a clade of phylotypes that have been retrieved from a range of geographically and ecologically distinct hypersaline environments. Strain PropA T shared ¡90 % 16S rRNA gene sequence identity with cultured strains within the family Desulfobacteraceae. Cells of strain PropA T were rod-shaped and sometimes motile. The strain required NaCl for growth and grew at salinities up to 200 g NaCl l "1 (optimum 60 g l "1). Growth was observed at 15-40 6C, optimum growth occurred at about 40 6C, while growth was absent at 10 and 45 6C. The pH range for growth was pH 6.0-8.3. Yeast extract (0.1 g l "1) was required for growth. C 2-4 alcohols, C 3-4 carboxylic acids, yeast extract and H 2 /acetate supported growth with sulfate as electron acceptor. Sulfate, thiosulfate and sulfite served as electron acceptors, but not elemental sulfur, nitrate or fumarate. The DNA G+C content of strain PropA T was 54.1 mol%. Based on the genotypic and physiological properties, we propose that strain PropA T represents a novel species within a novel genus, Desulfosalsimonas propionicica gen. nov., sp. nov. The type strain of Desulfosalsimonas propionicica is PropA T (5DSM 17721 T 5VKM B-2385 T).
Environmental Science & Technology, Mar 3, 2004
The oxygen tolerance of sulfate-reducing bacteria (SRB) present in activated sludge was studied i... more The oxygen tolerance of sulfate-reducing bacteria (SRB) present in activated sludge was studied in batch incubations using radiolabeled [ 35 S]sulfate and a most probable number (MPN) technique employing activated sludge medium. Sulfate reduction (SR) could not be detected in activated sludge during oxic incubation or in the presence of nitrate. However, upon anoxic incubation of both freshly sampled activated sludge and activated sludge preaerated for 40 min, SR resumed immediately at an initial rate of 2 µM h-1. During long-term aeration of activated sludge, the number of viable and culturable SRB remained constant at around 10 6 SRB mL-1 throughout a 121 h aeration period. During the first 9 h of the 121 h aeration period, the anaerobic SR activity was unaffected, as compared to that of an unaerated control sample, and recommenced instantaneously upon anoxic incubation. Even after 121 h of continuous aeration, SR took place within 1.5 h after anoxic incubation albeit at a rate less than 20% that of the unaerated control. As suggested by MPN estimates and the observed kinetics of SR, oxygen exposure resulted in temporary metabolic inactivation of SRB but did not cause cell death. Consequently, SRB have the potential for quick proliferation during anoxic storage of activated sludge.
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Papers by Kjeld Ingvorsen