Silva Fennica. A quarterly journal of forest science. Contents Vol. 28, 1994.

Julkaistu Silva Fennica Vol. 28(4) -numeron liitteenä.

Eutrophication of the Finnish coastal waters : origin, fate and effects of riverine nutrient fluxes

Suomen rannikkovesien rehevöityminen: jokivesien tuomien ravinteiden alkuperä, käyttäytyminen ja vaikutukset.

Mykorritsa fosforin kierrättäjänä

Suomen maatalousmaihin kertynyttä fosforia hyödynnetään tehottomasti, ja samalla muokkauskerroksen suuri fosforimäärä on alttiina huuhtoutumiselle. Arbuskelimykorritsaa (AM) hyödyntämällä on mahdollista tehostaa viljelykasvin fosforinottoa ja kasvua, ja siten vähentää fosforin huuhtoutumista. Tämän tutkielman tavoitteena oli selvittää mykorritsan vaikutus kasvin kasvuun ja fosforinottoon karjanlantalannoituksella mineraalilannoitukseen verrattuna sekä näiden lannoitusten pitkäaikaisvaikutusta AM-sieniyhteisöihin. Jotta lannoituskäytäntöjen vaikutus mykorritsaan voitiin suhteuttaa muihin maan laatutekijöihin, näiden käytäntöjen vaikutus myös satomääriin sekä muihin maan laatumittareihin arvioitiin. Pitkäaikainen kenttäkoe perustettiin kolmelle paikkakunnalle Pohjois-Ruotsissa vuosina 1965–66. Kuusivuotinen viljelykierto koostui joko viisivuotisesta nurmesta ja ohrasta tai ohramonokulttuurista. Lannoituskäsittelyt 32-vuoden ajan olivat suositusten mukainen (NPK) ja edelliseen nähden kaksinkertainen (2NPK) mineraalilannoitus sekä karjanlantalannoitus (KL), jonka ravinnemäärä vastasi NPK -käsittelyä. Kolmen lannoituskäsittelyn vaikutusta mykorritsan tehokkuuteen kasvin kasvun ja fosforiravitsemuksen näkökulmasta tutkittiin astiakokeissa. Mykorritsasieniyhteisöjen toiminnallisten erojen selvittämiseksi tehtiin takaisin- ja ristiinsiirrostuskoe. (5 v-%) steriloitua maanäytettä NPK- ja KL -käsittelyistä siirrostettiin käsittelemättömiin maanäytteisiin, jotka olivat samoista lannoituskäsittelyistä. Mykorritsan positiivinen vaikutus kasvin kasvuun ja fosforiravitsemukseen oli suurin kun käytettiin karjanlantaa. NPK ja 2NPK -käsittelyiden välillä ei havaittu eroja. Takaisin- ja ristiinsiirrostuskokeessa ei ollut tilastollisesti merkitseviä eroja. Nurmi- ja ohrasadot olivat suurimmat kun mineraalilannoitetta annettiin suosituksiin nähden kaksinkertainen määrä. Satomäärät olivat yhtä suuret tai suuremmat kun käytettiin karjanlantaa NPK –lannoituksen sijaan. Karjanlantakäsittely lisäsi maaperän kokonaishiili- ja kokonaistyppipitoisuutta verrattuna NPK -käsittelyyn, joka sisälsi saman määrän ravinteita. Samalla huuhtoutumiselle altis liukoisen fosforin pitoisuus säilyi alhaisella tasolla. Karjanlanta edisti mykorritsan toimintaedellytyksiä, ja siksi mykorritsasta saatua hyötyä fosforinotossa ja kasvuvaikutuksena mineraalilannoitteisiin verrattuna, mutta se ei vaikuttanut mykorritsasieniyhteisön toiminnallisiin ominaisuuksiin. Karjanlantalannoitus paransi mitattuja maan ominaisuuksia kokonaisuudessaan, eikä se vähentänyt satoja.

Characteristic water contents of a fine-grained soil-water system

This paper critically appraises the limitations of the liquid-limit water content of clayey soils determined conventionally either by percussion cup or by the cone penetration method. It is shown that the conventional liquid limit and plastic limit are arbitrary, strength-based water contents and that they cannot represent the plasticity limits, and that the state of the soil-water system at the conventional liquid limit does not correspond to a stress-free reference state. The present investigation identifies three characteristic limiting water contents for a soil-water system which have well-defined, unique mechanisms controlling them, namely the free swell limit, settling limit and shrinkage limit. Simple procedures for the determination of the free swell limit and settling limit of natural soils are presented. The settling limit is shown to be the 'real liquid limit' of any clayey soil. With a number of experimental illustrations, it is clearly shown that the settling limit represents the maximum water-holding capacity of clayey soils and that it corresponds to the stress-free reference state.

A full-length bifunctional protein involved in c-di-GMP turnover is required for long-term survival under nutrient starvation in Mycobacterium smegmatis

The bacterial second messenger cyclic diguanosine monophosphate (c-di-GMP) plays an important role in a variety of cellular functions, including biofilm formation, alterations in the cell surface, host colonization and regulation of bacterial flagellar motility, which enable bacteria to survive changing environmental conditions. The cellular level of c-di-GMP is regulated by a balance between opposing activities of diguanylate cyclases (DGCs) and cognate phosphodiesterases (PDE-As). Here, we report the presence and importance of a protein, MSDGC-1 (an orthologue of Rv1354c in Mycobacterium tuberculosis), involved in c-di-GMP turnover in Mycobacterium smegmatis. MSDGC-1 is a multidomain protein, having GAF, GGDEF and EAL domains arranged in tandem, and exhibits both c-di-GMP synthesis and degradation activities. Most other proteins containing GGDEF and EAL domains have been demonstrated to have either DGC or PDE-A activity. Unlike other bacteria, which harbour several copies of the protein involved in c-di-GMP turnover, M. smegmatis has a single genomic copy, deletion of which severely affects long-term survival under conditions of nutrient starvation. Overexpression of MSDGC-1 alters the colony morphology and growth profile of M. smegmatis. In order to gain insights into the regulation of the c-di-GMP level, we cloned individual domains and tested their activities. We observed a loss of activity in the separated domains, indicating the importance of full-length MSDGC-1 for controlling bifunctionality.

Lead Retention by Soils at Field Moisture Contents

The majority of studies pertaining to lead retention by clays and soils have examined the mechanisms, kinetics, and adsorption isotherms using the batch experiment technique that employs solid: water extracts of 1:10 and 1:20. Field soil deposits generally have much lower gravimetric water content ranging between 9 and 45%. Given the wide disparity in the solids: water ratio employed in the batch experiment technique and that prevailing in field deposits, this paper examines the lead retention characteristics of soils at field moisture contents (6%, 13%, and 25%) using artificially lead-contaminated soil specimens. A residually derived (i.e., formed by in-situ weathering of parent rock) red soil was used to prepare the artificially contaminated soil specimens. The impact of variations in clay content on lead retention was examined by diluting the residual soil with various amounts (0 to 60%) of river sand. Soil specimens remolded at 6 and 13% moisture contents produced very stiff to hard soils on compaction, while specimens remolded at 25% moisture content existed in the slurry state. The soil specimens were contaminated with low (30mg/kg) to high (2500mg/kg) concentrations of lead ions by remolding them with 160ppm to 10,000ppm ionic lead solutions. Lead retention by soils at field moisture contents was determined by extracting the lead from the soil using a water leach test. Experimental results showed that the bulk (71 to 99%) of the added lead was retained by the soil in insoluble form at the field moisture content. Correlations between the amount of lead retained and soil/solution parameters indicated that the amounts of Pb retained at field moisture content is a function of the initial Pb addition, total sand content, effective clay porosity, and soil pH.

Euglena sp as a suitable source of lipids for potential use as biofuel and sustainable wastewater treatment

Prolific algal growth in sewage ponds with high organic loads in the tropical regions can provide cost-effective and efficient wastewater treatment and biofuel production. This work examines the ability of Euglena sp. growing in wastewater ponds for biofuel production and treatment of wastewater. The algae were isolated from the sewage treatment plants and were tested for their nutrient removal capability. Compared to other algae, Euglena sp. showed faster growth rates with high biomass density at elevated concentrations of ammonium nitrogen (NH4-N) and organic carbon (C). Profuse growth of these species was observed in untreated wastewaters with a mean specific growth rate (mu) of 0.28 day(-1) and biomass productivities of 132 mg L-1 day(-1). The algae cultured within a short period of 8 days resulted in the 98 % removal of NH4-N, 93 % of total nitrogen 85 % of ortho-phosphate, 66 % of total phosphate and 92 % total organic carbon. Euglenoids achieved a maximum lipid content of 24.6 % (w/w) with a biomass density of 1.24 g L-1 (dry wt.). Fourier transform infrared spectra showed clear transitions in biochemical compositions with increased lipid/protein ratio at the end of the culture. Gas chromatography and mass spectrometry indicated the presence of high contents of palmitic, linolenic and linoleic acids (46, 23 and 22 %, respectively), adding to the biodiesel quality. Good lipid content (comprised quality fatty acids), efficient nutrient uptake and profuse biomass productivity make the Euglena sp. as a viable source for biofuel production in wastewaters.

Lactoylglutathione lyase, a critical enzyme in methylglyoxal detoxification, contributes to survival of Salmonella in the nutrient rich environment

Glyoxalase I which is synonymously known as lactoylglutathione lyase is a critical enzyme in methylglyoxal (MG) detoxification. We assessed the STM3117 encoded lactoylglutathione lyase (Lgl) of Salmonella Typhimurium, which is known to function as a virulence factor, due in part to its ability to detoxify methylglyoxal. We found that STM3117 encoded Lgl isomerises the hemithioacetal adduct of MG and glutathione (GSH) into S-lactoylglutathione. Lgl was observed to be an outer membrane bound protein with maximum expression at the exponential growth phase. The deletion mutant of S. Typhimurium (lgl) exhibited a notable growth inhibition coupled with oxidative DNA damage and membrane disruptions, in accordance with the growth arrest phenomenon associated with typical glyoxalase I deletion. However, growth in glucose minimal medium did not result in any inhibition. Endogenous expression of recombinant Lgl in serovar Typhi led to an increased resistance and growth in presence of external MG. Being a metalloprotein, Lgl was found to get activated maximally by Co2+ ion followed by Ni2+, while Zn2+ did not activate the enzyme and this could be attributed to the geometry of the particular protein-metal complex attained in the catalytically active state. Our results offer an insight on the pivotal role of the virulence associated and horizontally acquired STM3117 gene in non-typhoidal serovars with direct correlation of its activity in lending survival advantage to Salmonella spp.

Interrelationship between Interphase Boundaries and Phase Contents near the Critical Compositions of Lead-Free Ferroelectric (Na0.5Bi0.5)TiO3-BaTiO3

Heterophase structures in lead-free perovskite-type ferroelectric solid solutions of (1 - z)(Na0.5Bi0.5)TiO3 - zBaTiO(3) are analysed for a few critical compositions near the morphotropic phase boundary (z = 0.05-0.07). Examples of the phase coexistence and elastic matching of the phases from different symmetry groups are considered to find optimum volume fractions of specific domain types and coexisting phases at the complete stress relief in two-phase samples. Some interrelations between these volume fractions are described using variants of the domain arrangement at changes in the composition and unit-cell parameters. The evaluated room-temperature volume fractions of the ferroelectric monoclinic (Cm symmetry) and tetragonal (P4mm symmetry) phases near the morphotropic phase boundary are in agreement with experimental data.