Morten Miller - Academia.edu (original) (raw)

Papers by Morten Miller

Applied and Environmental Microbiology, 2003

Two mold species, Stachybotrys chartarum and Aspergillus versicolor, were inoculated onto agar ov... more Two mold species, Stachybotrys chartarum and Aspergillus versicolor, were inoculated onto agar overlaid with cellophane, allowing determination of a direct measurement of biomass density by weighing. Biomass density, ergosterol content, and beta-N-acetylhexosaminidase (3.2.1.52) activity were monitored from inoculation to stationary phase. Regression analysis showed a good linear correlation to biomass density for both ergosterol content and beta-N-acetylhexosaminidase activity. The same two mold species were inoculated onto wallpapered gypsum board, from which a direct biomass measurement was not possible. Growth was measured as an increase in ergosterol content and beta-N-acetylhexosaminidase activity. A good linear correlation was seen between ergosterol content and beta-N-acetylhexosaminidase activity. From the experiments performed on agar medium, conversion factors (CFs) for estimating biomass density from ergosterol content and beta-Nacetylhexosaminidase activity were determined. The CFs were used to estimate the biomass density of the molds grown on gypsum board. The biomass densities estimated from ergosterol content and beta-N-acetylhexosaminidase activity data gave similar results, showing significantly slower growth and lower stationaryphase biomass density on gypsum board than on agar.

Soil Biology and Biochemistry, 1999

Fungal±bacterial interaction on decomposing beech leaves was investigated in a microcosm experime... more Fungal±bacterial interaction on decomposing beech leaves was investigated in a microcosm experiment. Sterilised 1 yr old leaves were inoculated with microbial populations isolated from beech forest soil: bacteria (inoculum B), fungi and bacteria (inoculum F + B), a cellulolytic Humicola sp. (inoculum H) and this fungus together with bacteria (inoculum H + B), respectively. The data for mineralization rates and fungal activities, the latter determined by a new enzymatic tool, suggested antagonistic interaction between fungi and bacteria. Carbon transformation in the microcosms, estimated as C mineralized plus net dissolved organic carbon (DOC) formation, was consistently higher when fungi were present in the inoculum as compared to a diverse community of bacteria acting alone. DOC quality was determined as the ability of the carbon to support denitri®cation with excess nitrate. The DOC quality was dependent on the inoculum type: B and F + B treatments resulted in similar DOC quality, but when the Humicola sp. was present (H and H + B treatment) the quality was low. Thus, in spite of the higher fungal carbon transformation a fungal-mediated¯ush of DOC made available to heterotrophic bacteria was not observed. Taking all data into account, the antagonistic interaction between fungi and bacteria was most likely explained by competition for C substrate. #

NAGase activity was expressed only in a limited number of bacteria and on media supplemented with... more NAGase activity was expressed only in a limited number of bacteria and on media supplemented with chitin. The CELase activity was observed only in a limited number of fungi and bacteria. Bacterial CELase activity was expressed on agar media containing a cellulose-derived substrate. In soil samples, NAGase activity was significantly correlated with estimates of fungal biomass, based on the content of two fungus-specific indicator molecules, 18:26 phospholipid fatty acid (PLFA) and ergosterol. CELase activity was significantly correlated with the PLFA-based estimate of fungal biomass in the soil, but no correlation was found with ergosterol-based estimates of fungal biomass.

Journal of Microbiological Methods, 1999

Plots of an alpine grassland in the Swiss Alps were treated with elevated (680 ml l ) and ambient... more Plots of an alpine grassland in the Swiss Alps were treated with elevated (680 ml l ) and ambient CO (355 ml l ) in 2 open top chambers (OTC). Several plots were also treated with NPK-fertilizer. Community level physiological profiles (CLPPs) of the soil bacteria were examined by Biolog GN microplates and enzyme activities were determined through the release of methylumbelliferyl (MUF) and methylcoumarin (MC) from MUF-or MC-labelled substrates. A canonical discriminant analysis (CDA) followed by multivariate analysis of variance showed a significant effect of elevated CO on the CLPPs both under fertilized and unfertilized conditions. Further, the installation of the OTCs caused 2 significant shifts in the CLPPs (chamber effect). Of the four enzyme activities tested, the b-D-cellobiohydrolase (CELase) and N-acetyl-b-D-glucosaminidase (NAGase) activity were enhanced under elevated CO . L-Leucin-7-aminopeptidase 2 (APEase) activity decreased, when the plots received fertilizer. b-D-Glucosidase (GLUase) remained unaffected.

Soil Biology & Biochemistry - SOIL BIOL BIOCHEM, 1995

Soil samples were collected to a depth of 10 cm in 1991 and 1993 from a vegetable crop rotation e... more Soil samples were collected to a depth of 10 cm in 1991 and 1993 from a vegetable crop rotation experiment initiated in 1989. The two cropping treatments, with either 0 or 280 kg N ha−1, represented the traditional vegetable rotation (TVR) and an alternative legume vegetable rotation (LVR) when a vegetable crop alternated with a red clover (Trifolium pratense L.) seed-crop that was incorporated as green manure in the following spring. The enzyme activities of L-asparaginase, amidase and β-glucosidase were determined on whole soil and five soil aggregate size fractions: 1.00–2.00, 0.50–1.00, 0.25–0.50, 0.10–0.25 and <0.1 mm. Thermal stability of the enzymes was determined by conditioning soil samples at 85°C for 2 h or by exposing soil samples to five successive freeze-thaw cycles prior to enzyme assays. Enzyme activities for LVR were significantly greater (P < 0.05) than TVR for β-glucosidase and amidase at both N-rates in 1991. This difference in activity for these enzymes was sustained only at the high N-rate in 1993. The activity of L-asparaginase was significantly higher (P < 0.01) in the LVR in 1993. Sixty to seventy percent of the soil enzyme activity (on a mass basis) was associated with macroaggregates with specific distribution of activity across aggregate fractions varying with enzyme. Average β-glucosidase activity decreased by 50% from 1991 to 1993. In contrast, amidase activity increased 1.43-fold over the same period. β-glucosidase activity was sensitive to temporal trends, showing proportional decreases in activities in each system that were consistent with decreases in organic C. Furthermore, β-glucosidase activity showed significantly higher (P < 0.05) resistance to heat-induced thermal stress in the LVR in both sampling years. Amidase and L-asparaginase activities showed no such treatment effects. The results showed that soil enzyme activity is a sensitive biological indicator of the effects of soil management practices.

Biology and Fertility of Soils, 2001

... Amino acids and peptides are the largest pool of soil organic N identifiable after acid hydro... more ... Amino acids and peptides are the largest pool of soil organic N identifiable after acid hydrolysis (Stevenson 1982). As ammonia release (ammonification) during ami-... ORIGINAL PAPER Torben A. Bonde · Tommy Harder Nielsen Morten Miller · Jan Sørensen ...

Applied Soil Ecology, 2001

Formamide hydrolase activity in a barley field soil was described by a two-component, rather than... more Formamide hydrolase activity in a barley field soil was described by a two-component, rather than a one-component model of Michaelis-Menten kinetics. The two-component model had both a high-affinity (K m values of 0.5-1.0 mM) and a low-affinity (K m values of 30-60 mM) activity. Rapid and transient increases in both the overall heterotrophic activity (CO 2 production) and the high-affinity component of formamide hydrolase activity were observed in rewetted soil samples, suggesting that the high-affinity component represented enzyme activity of active microorganisms. Short-term field variations in the high-affinity component during a barley growth season were consistent with rapid, transient responses of microbial activity to precipitation and soil wetting. An assay of the high-affinity component of formamide hydrolase activity as approximated by rate determination at a single low (1 mM) formamide concentration can provide an easy and rapid indication of enzyme activity related directly to active microorganisms in the soil.

Applied Soil Ecology, 1995

... 4. Discussion Positive effects of leguminous crops on aggregate stabilization and formation h... more ... 4. Discussion Positive effects of leguminous crops on aggregate stabilization and formation have been attributed to enhanced root activity and incorporation of legumes as green manure (Dufeyet al., 1986; Latif et al., 1992). Carter and Kunelius (1993) found a six to 11fold ...