Biomedical subjects

V Sundman

Publications and source records attributed to V Sundman.

13 recordsLinked to original sources

PubMed1983

Nitrogenase activity (acetylene reduction) of root-associated, cold-climate azospirillum, enterobacter, Klebsiella, and pseudomonas species during growth on various carbon sources and at various partial pressures of oxygen.

A comprehensive view of the diazotrophic bacterial flora of plants requires that attention be paid to the appropriate carbon and oxygen requirements during isolation of the bacteria. Twenty compounds (monosaccharides, disaccharides, polyols, and organic acids) were therefore examined as carbon and energy sources for nitrogenase activity in semisolid stab cultures at pO(2) values of 0.21, 0.02, and </=0.002 with 12 strains of diazotrophic root-associated bacteria. With the facultatively anaerobic bacteria of the genera Klebsiella and Enterobacter, the best substrate was sucrose, followed by fructose and mannitol, whereas among the organic acids, only malic and fumaric acids supported any activity. With the obligately aerobic bacteria of the genera Azospirillum and Pseudomonas, disaccharides were not utilized for nitrogen fixation, but several organic acids were accepted in addition to monosaccharides and polyols; malate and glucose were the best substrates. The patterns of the carbon sources utilized for nitrogen fixation were coherent within the species, with the exception of one Klebsiella pneumoniae and one Enterobacter agglomerans strain, both isolated from the same individual grass plant, which were unable to utilize lactose. Anaerobic conditions (pO(2) value of </=0.002) were required for maximum nitrogenase activity with the facultatively anaerobic bacteria, with the exception of one strain of E. agglomerans, which required atmospheric oxygen (pO(2) value of 0.21). Also, the obligately aerobic diazotrophs required atmospheric oxygen for maximum nitrogenase activity. The maximum specific nitrogenase activities (expressed as micromoles of C(2)H(4) . milligram of bacterial protein . hour) noted during the exponential growth phase of the bacteria were the following: 2.68 with Azospirillum lipoferum on malate, 2.41 with K. pneumoniae and 1.58 with E. agglomerans on sucrose, and 0.95 with Pseudomonas sp. on malate.

Journal Article↗

PubMed1983

Morphological and physiological characteristics and lipopolysaccharide composition of N2-fixing (C2H2-reducing) root-associated Pseudomonas sp.

A dinitrogen-fixing Pseudomonas sp. was isolated from the roots of the grass Deschampsia caespitosa. The motile organism, which had 4 to 10 polar flagella, was gram negative, obligately aerobic, oxidase positive, arginine dihydrolase positive, and fluorescent. To verify API20B, API20E, and Oxi-Ferm identifications, as well as results from standard microbiological tests and electron microscopic examinations, which all indicated the organism to be a Pseudomonas, we analyzed its lipopolysaccharide. The lipopolysaccharide contained neutral sugars, phosphorus, heptose, hexosamine, 2-keto-3-deoxyoctonate, and fatty acids, which were dodecanoic, 3-hydroxydecanoic, 2-hydroxydodecanoic, and 3-hydroxydodecanoic acids. Both the qualitative and quantitative compositions resembled known data of the genus Pseudomonas. Dinitrogen fixation, determined as C2H2 reduction in semisolid medium, was supported by several carbon sources including malate and glucose. The N2 fixation activity was decreased if the oxygen concentration of the gas phase was lowered to one-tenth of atmospheric concentration. The highest specific nitrogenase activity recorded was 954 nmol C2H4/mg bacterial protein per hour, which is about 30% of that noted for Azospirillum lipoferum used as reference.

Acetylene↗

PubMed1981

Root-associated n(2) fixation (acetylene reduction) by enterobacteriaceae and azospirillum strains in cold-climate spodosols.

N(2) fixation by bacteria in associative symbiosis with washed roots of 13 Poaceae and 8 other noncultivated plant species in Finland was demonstrated by the acetylene reduction method. The roots most active in C(2)H(2) reduction were those of Agrostis stolonifera, Calamagrostis lanceolata, Elytrigia repens, and Phalaris arundinacea, which produced 538 to 1,510 nmol of C(2)H(4).g (dry weight). h when incubated at pO(2) 0.04 with sucrose (pH 6.5), and 70 to 269 nmol of C(2)H(4). g (dry weight).h without an added energy source and unbuffered. Azospirillum lipferum, Enterobacter agglomerans, Klebsiella pneumoniae, and a Pseudomonas sp. were the acetylene-reducing organisms isolated. The results demonstrate the presence of N(2)-fixing organisms in associative symbiosis with plant roots found in a northern climatic region in acidic soils ranging down to pH 4.0.

Journal Article↗

PubMed1980

Denitrification in Low pH Spodosols and Peats Determined with the Acetylene Inhibition Method.

Potential denitrification rates were determined for predominantly acid (pH >/= 3.6) horizons of forestal, miry, and agricultural soils from 22 locations in southern Finland. The acetylene inhibition method was used with nitrate-amended water-logged soils incubated in an N(2) atmosphere containing 2.5 or 5% C(2)H(2). Complete inhibition of the reduction of N(2)O to N(2) was observed in 99.3% of the samples. The denitrification rates varied from 0.12 to 53.8 mug of N.cm.day. Correlation between denitrification rate and soil pH was highly significant: r = 0.84 on a volume basis, and r = 0.44 on a weight basis. Vegetation type and amount of soil organic matter had a minor or no effect, respectively. In spodosolized soils the rates were significantly higher for B horizons than for A horizons. These results show that denitrification can occur in acid soils.

Journal Article↗

PubMed1979

Partial characterization of a new C3-type capsule-dissolving phage of Streptococcus cremoris.

A viscous, ropy, sour milk product, called 'viili,' is produced in Finland. Capsule-forming strains of Streptococcus cremoris are the typical starters for this product. Occasionally fermentation fails and results in a non-ropy clot. The reasons for these failures, however, are obscure. In one batch of spoiled 'viili,' a new C3-type bacteriophage, termed KSY1, was isolated. The head of the phage was about 230 nm long and about 50 nm wide and the tail was 35 nm long and carried a complex collar structure. Upon infection of a number of encapsulated cultures of S. cremoris with KSY1, the cocci, though not serving as a host of the phage, lost their capsules. A capsuleless strain, S. cremoris 249, served as a host. The latent period was about 150 min and the average burst size 80. The bouyant density of KSYI1 was 1.436 g/cm3.

Animals↗

PubMed1978

Screening for lignin degrading bacteria by means of 14C-labelled lignins.

Several Nocardia and Pseudomonas spp., as well as some unidentified bacteria, isolated from lake water containing high loads of waste lignin, were tested for their capacity to release 14CO2 from specifically 14C-labelled dehydropolymer of coniferyl alcohol (DHP) or corn stalk lignins. The bacteria were selected according to their ability to degrade phenolic compounds. However, only some of them could release significant amounts of 14CO2 from the labelled lignin. The tested Nocardia spp. were more active than the Pseudomonas spp. and the unidentified bacteria. The most active strains belonged to N. autotrophica. These strains released CO2 significantly from the methoxyl group and transformed the other carbons from the phenylpropane skeleton of lignin also into CO2. Other less demethylating strains also released little CO2 from the other carbons of the lignin molecule. From corn stalk materials which were specifically labelled in the lignin part, only small amounts of labelled CO2 were released.

Biodegradation, Environmental↗

PubMed1977

Decomposition of 14C-labelled lignin and phenols by a Nocardia sp.

A Gram-positive bacterium which was isolated from a Finnish soil and identified as a Nocardia sp., was able to decompose lignin and to assimilate lignin degradation products as a carbon source. It could release 14CO2 from 14C-labelled methoxyl groups, side chains or ring carbons of coniferyl alcohol dehydropolymers (DHP) and from specifically 14C-labelled lignin of plant material. Furthermore, it could release 14CO2 from phenolcarboxylic and cinnamic acids and alcohols labelled in the OCH3, COOH groups, side chain or aromatic ring carbons.

Carbon Dioxide↗

PubMed1977

Effects of clear-cutting on the composition of bacterial populations of northern spruce forest soil.

This paper concerns the microbiological part of an investigation, the goal of which is to describe the biological changes in coniferous forest soil upon clear-cutting in a northern (66 degrees 20'N) moraine area where reforestation after clear-cutting had been met with difficulty. The zoological part of the work has been published elsewhere. Clear-cut sites of increasing age (4, 7, and 13 years) were investigated and compared with a forest area where no cutting of timber had been done for 120 years. A total of 684 random isolates of heterotrophic bacteria from pooled samples of the sites investigated were passed through 36 biochemical tests. The data were condensed by the aid of factor analysis, and a comparison of the populations was based on squared Euclidean distances between population centroids in a seven-dimensional factor space. The most marked population changes followed a course in which frequencies of some population characteristics became increasingly different until 7 years after clear-cutting, with regression towards the control clearly evident after 13 years. Disturbances of shorter duration were also relatively common, with maximal changes observed in the 4-year samples, and with a complete recovery after 7 years. The mineral soil populations seemed to undergo greater changes than the humus populations. The most distinct changes believed to be due to clear-cutting were the short-term relative increase of organisms producing acid from sucrose and dissolving CaHPO4, and a long-term increase of lipolytic and caseolytic, rhamnose-negative organisms; both in the mineral soil layer. In the humus layer, a short-term increase of lipolytic and of rhamnose-positive organisms seemed to take place.

Analysis of Variance↗

PubMed1970