Isolation and characterisation of porin from the outer membrane of Synechococcus PCC 6301

Pore-forming protein (porin) was isolated from N,N-dimethyl-dodecylaminoxid (LDAO)-extracted outer membranes of Synechococcus PCC 6301 and purified by ion exchange chromatography on DEAE-Sephacel column. The apparent molecular mass on SDS-PAGE was determined to be about 52000. The native porin was reconstituted into black lipid bilayer membranes and showed a single-channel conductance of 5.5 nS in 1 M KCl. The porin was found to be N-terminally blocked. The C-terminal amino acid sequence was identified as Phe-Thr-Phe. Amino acid analysis suggested that the porin protein consists of about 420 amino acid residues, yielding a polarity of 43.6% and a molecular mass of 45000 in contrast to the mobility on SDS-PAGE.Abbreviations DEAE Diethylaminoethyl; M _r, relative molecular mass - LDAO N,N-Dimethyl-dodecylaminoxid - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoretogram - PCC Pasteur Culture Collection - SDS sodium dodecyl sulfate - UTEX Culture Collection of Algae at the University of Texas     

Alder and lupine enhance nitrogen cycling in a degraded forest soil in Northern Sweden

Positive effects of legumes and actinorhizal plants on N-poor soils have been observed in many studies but few have been done at high latitudes, which was the location of our study. We measured N₂ fixation and several indices of soil N at a site near the Arctic Circle in northern Sweden. More than 20 years ago lupine (Lupinus nootkatensis Donn) and gray alder (Alnus incana L. Moench) were planted on this degraded forest site. We measured total soil N, net N mineralization and nitrification with a buried bag technique, and fluxes of NH⁺ ₄ and NO^– ₃ as collected on ion exchange membranes. We also estimated N₂ fixation activity of the N₂-fixing plants by the natural abundance of ¹⁵N of leaves with Betula pendula Roth. as reference species. Foliar nitrogen in the N₂-fixing plants was almost totally derived from N₂ fixation. Plots containing N₂-fixing species generally had significantly higher soil N and N availability than a control plot without N₂-fixing plants. Taken together, all measurements indicated that N₂-fixing plants can be used to effectively improve soil fertility at high latitudes in northern Sweden.     

Deletion mutations in a long hydrophilic loop in the photosystem II chlorophyll-binding protein CP43 in the cyanobacterium Synechocystis sp. PCC 6803

In order to investigate the role and function of the hydrophilic region between transmembrane regions V and CI in the photosystem II core antenna protein CP43, we introduced eight different deletions in psbC of Synechocystis sp; PCC 6803 resulting in a loss of 7–11 codons in evolutionary conserved domains in this region. All deletions resulted in an obligate photoheterotrophic phenotype (requirement of glucose for cell growth) and the absence of any detectable oxygen evolution activity. The various deletion mutations showed a different impact on the amount of CP43 in the thylakoid, ranging from wild-type levels of (a now slightly smaller) CP43 to no detectable CP43 at all. All deletions led to a decrease in the amount of the D1 and D2 proteins in the thylakoids with a larger effect on D2 than on D1. CP47, the other major chlorophyll-binding protein, was present in reduced but significant amounts in the thylakoid. Herbicide binding (diuron) was lost in all but one mutant indicating the PSII components are not assembled into functionally intact complexes. Fluorescence-emission spectra confirmed this notion. This indicates that the large hydrophilic loop of CP43 plays an important role in photosystem II, and even though a shortened CP43 is present in thylakoids of most mutants, functional characteristics resemble that of a mutant with interrupted psbC.Abbreviations CP chlorophyll-binding protein - DCPIP 2,6-dichlorophenolindophenol - DPC diphenylcarbazide - ferricyanide K₃Fe(CN)₆ - HEPES N-(2-hydroxyelthyl)piperazine-N-(2-hydroxypropane sulfonic acid) - MES 2-(N-morpholino)-ethanesulfonic acid - PCC Pasteur Culture Collection - PCR polymerase chain reaction - PS photosystem - Q_A first quinone acceptor in PSII - Q_B second quinone acceptor in PSII - Z redox-active tyrosine (Y161) in D1 serving as electron carrier between the Mn cluster and P680     

Nitrogen fixation associated with roots of Kallar grass (Leptochloa fusca L. Kunth)

Summary An ecological survey was made to measure the N₂-fixing activity in the rhizosphere of a salt-tolerant grass,Leptochloa fusca (L.) Kunth. Samples were obtained every month at two sites over a period of one year. Soil cores, unwashed, washed and surface-sterilized roots were subjected to acetylene reduction assay (ARA). ARA values up to 50 nmoles h^–1 for soil cores, 1095 nmoles g dry root^–1 h^–1 for unwashed roots, 4929 nmoles g dry root^–1 h^–1 for washed roots and 2494 nmoles g dry root^–1 h^–1 for surface-sterilized roots were observed but for most samples the range was 1–200 nmoles g dry root^–1 h^–1. A lag period of 5–7 h was observed before the onset of N₂-fixing activity by excised roots and O₂ levels had no effect on this lag. Values for roots incubated without preincubation were similar to those for unwashed preincubated roots. Activity was highest in September, October and November when the temperature is not very high and photosynthetic activity is reasonably good. N₂-fixing-bacteria were counted on the same samples by plate count and MPN methods, the latter being estimated on the basis of ARA and pellicle formation. Fairly high numbers of bacteria (10⁴–10⁷) were recorded in the histoplane fraction which indicates the presence of diazotrophs in the inner cells of grass roots.     

Sugar beet and barley yields in relation to inoculation with N2-fixing and phosphate solubilizing bacteria

Recently, there has been a resurgence of interest in bioorganic fertilizers as part of sustainable agricultural practices to alleviate drawbacks of intensive farming practices. N₂-fixing and P-solubilizing bacteria are important in plant nutrition increasing N and P uptake by the plants, and playing a significant role as plant growth-promoting rhizobacteria in the biofertilization of crops. A study was conducted in order to investigate the effects of two N₂-fixing (OSU-140 and OSU-142) and a strain of P-solubilizing bacteria (M-13) in single, dual and three strains combinations on sugar beet and barley yields under field conditions in 2001 and 2002. The treatments included: (1) Control (no inoculation and fertilizer), (2) Bacillus OSU-140, (3) Bacillus OSU-142, (4) Bacillus M-13, (5) OSU-140 + OSU-142, (6) OSU-140 + M-13, (7) OSU-142 + M-13, (8) OSU-140 + OSU-142 + M-13, (9) N, (10) NP. N and NP plots were fertilized with 120 kg N ha^–1 and 120 kg N ha^–1 + 90 kg P ha^- for sugar beet and 80 kg N ha^–1 and 80 kg N ha^–1 + 60 kg P ha^–1 for barley. The experiments were conducted in a randomized block design with five replicates. All inoculations and fertilizer applications significantly increased leaf, root and sugar yield of sugar beet and grain and biomass yields of barley over the control. Single inoculations with N₂-fixing bacteria increased sugar beet root and barley yields by 5.6–11.0% depending on the species while P-solubilizing bacteria alone gave yield increases by 5.5–7.5% compared to control. Dual inoculation and mixture of three bacteria gave increases by 7.7–12.7% over control as compared with 20.7–25.9% yield increases by NP application. Mixture of all three strains, dual inoculation of N₂-fixing OSU-142 and P-solubilizing M-13, and/or dual inoculation N₂-fixing bacteria significantly increased root and sugar yields of sugar beet, compared with single inoculations with OSU-140 or M-13. Dual inoculation of N₂-fixing Bacillus OSU-140 and OSU-142, and/or mixed inoculations with three bacteria significantly increased grain yield of barley compared with single inoculations of OSU-142 and M-13. In contrast with other combinations, dual inoculation of N₂-fixing OSU-140 and P-solubilizing M-13 did not always significantly increase leaf, root and sugar yield of sugar beet, grain and biomass yield of barley compared to single applications both with N₂-fixing bacteria. The beneficial effects of the bacteria on plant growth varied significantly depending on environmental conditions, bacterial strains, and plant and soil conditions.     

Growth yields of green sulfur bacteria in mixed cultures with sulfur and sulfate reducing bacteria

1. Dry weight yields from mixed cultures ofProsthecochloris aestuarii orChlorobium limicola with the sulfur reducingDesulfuromonas acetoxidans were determined on different growth limiting amounts of acetate, ethanol or propanol. The obtained yields agreed well with values predicted from stoichiometric calculations. 2. From mixed cultures of twoChlorobium limicola strains withDesulfovibrio desulfuricans orD. gigas on ethanol as the growth limiting substrate, dry weight yields were obtained as calculated for the complete utilization of the ethanol by the mixed cultures. 3. Dry weight yield determinations for two pure cultures ofChlorobium limicola with different growth limiting amounts of sulfide in the absence and presence of excess acetate confirmed that acetate is incorporated byChlorobium in a fixed proportion to sulfide; compared to the yield in the absence of acetate the yield is increased two to threefold in the presence of acetate. 4. The lowest possible sulfide concentrations necessary for optimal growth of mixed cultures of eitherProsthecochloris orChlorobium withDesulfuromonas on acetate were 7–8 mg H₂S per liter of medium. 5. Doubling times at the growth rate limiting light intensities of 5, 10, 20, 50, 100 and 200 lux were determined under optimal growth conditions for the following phototrophic bacteria:Prosthecochloris aestuarii, Chlorobium phaeovibriodes, Chromatium vinosum andRhodopseudomonas capsulata. Reasonably good growth was still obtained withProsthecochloris at 10 and 5 lux light intensity at which no growth of the purple bacteria could be observed.     

The relationship between the state of adenylylation of glutamine synthetase I and the export of ammonium in free-living,N2-fixing Rhizobium

The relationship between ammonium assimilation and ammonium export has been studied in free-living, N₂-fixing Rhizobium sp. 32H1. After 55 to 67 h of microaerobic growth under a gas phase of 0.2% O₂ – 1.0% CO₂ – 98.8% Ar high levels of nitrogenase were observed concomitant with a slightly adenylylated glutamine synthetase (GSI) and some glutamine synthetase (GSII) activity. However, after growth of 89 h, or longer, GSI became adenylylated and the level of GSII had decreased. When the gas phase was shifted to 0.2% O₂ – 1.0% CO₂ – 98.8% N₂, a lag was observed before ammonium export could be detected in the 55 to 67 h cultures. No lag in ammonium export was observed in the cultures previously grown for 89 h. The onset of ammonium export in the 55 to 67 h cultures was found to correlate with the adenylylation state of GSI. There appeared to be no correlation between the level of GSII and the export of ammonium. Neither an increase in the adenylylation level of GSI nor ammonium export was observed when the 55 to 67 h cultures were maintained under the Ar gas mixture.Abbreviations GOGAT Glutamate synthase - GS glutamine synthetase - BES [N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid] - CTAB cetyltrimethylammonium bromide - MES [2-(N-morpholino)-ethane sulfonic acid]     

Survival and colonization of inoculated bacteria in kallar grass rhizosphere and quantification of N2-fixation

Two experiments have been conducted, one in semi-solid Hoagland nutrient medium and the other in shallow pots containing saline soil. N₂-fixing bacteria belonging toAzospirillum, Azotobacter, Klebsiella andEnterobacter were inoculated separately on kallar grass grown in semi-solid nutrient medium. It was shown that inoculation affects root proliferation and also results in¹⁵N isotopic dilution. The % Ndfa ranged from 47–70 whereas no significant effect on the total nitrogen uptake was observed. The bacterial colonization of the root surface and the presence of enteric bacteria inside the root hair cells is reported. In a soil pot experiment, non-N₂-fixingPolypogon monspeliensis was used as a reference plant (control). A treatment receiving a high rate of nitrogen was also used as a non-N₂-fixing control.¹⁵N-labelled ammonium sulphate at 20 kg N ha^–1 and 90 kg N ha^–1 was used. The % Ndfa in the aerial parts of kallar grass was 12–15 whenP. monspeliensis was used as reference plant whereas 37–39% Ndfa was estimated when the treatment receiving high nitrogen fertilizer was used as a non-N₂-fixing control. These investigations revealed some problems of methodology which are discussed.     

Growth physiology of a marine nitrogen-fixing cyanobacterium (Nodularia harveyana) in outdoor culture

The performance ofNodularia harveyana, a N₂-fixing cyanobacterium isolated from seawater, has been studied outdoors in two different culture systems: open pond (OP) and tubular photobioreactor (TPR). The productivity in both devices was influenced by areal density. The maximum yield obtained was 12.0 g (d.wt) m^–2 day^–1 in OP and 14.0 g (d.wt) m^–2 day^–1 in TPR in August, corresponding to the highest solar radiation received. In a month-long experiment with the cyanobacterium cultivated in TPR at high circulation speed, a net increase in productivity was obtained over that at low circulation speed. The influence of temperature on the productivity of the cultures grown in open ponds and tubular photobioreactors has been investigated. The higher productivity obtained in TPR compared to OP was attributed to its better controlled temperature conditions. In outdoor culture the maximum nitrogenase activity did not coincide with the maximum light intensity, but occurred in early afternoon. The amount of carbohydrate accumulated during the day probably influenced the rate of dark nitrogenase activity and its duration in the night.     

Nitrogen fixation in perennial forage legumes in the field

Nitrogen acquisition is one of the most important factors for plant production, and N contribution from biological N₂ fixation can reduce the need for industrial N fertilizers. Perennial forages are widespread in temperate and boreal areas, where much of the agriculture is based on livestock production. Due to the symbiosis with N₂-fixing rhizobia, perennial forage legumes have great potential to increase sustainability in such grassland farming systems. The present work is a summary of a large number of studies investigating N₂ fixation in three perennial forage legumes primarily relating to ungrazed northern temperate/boreal areas. Reported rates of N₂ fixation in above-ground plant tissues were in the range of up to 373 kg N ha^–1 year^–1 in red clover (Trifolium pratense L.), 545 kg N ha^–1 year^–1 in white clover (T. repens L.) and 350 kg N ha^–1 year^–1 in alfalfa (Medicago sativa L.). When grown in mixtures with grasses, these species took a large fraction of their nitrogen from N₂ fixation (average around 80%), regardless of management, dry matter yield and location. There was a large variation in N₂ fixation data and part of this variation was ascribed to differences in plant production between years. Studies with experiments at more than one site showed that also geographic location was an important source of variation. On the other hand, when all data were plotted against latitude, there was no simple correlation. Climatic conditions seem therefore to give as high N₂ fixation per ha and year in northern areas (around 60°N) as in areas with a milder climate (around 40°N). Analyzing whole plants or just above-ground plant parts influenced the estimate of N₂ fixation, and most reported values were underestimated since roots were not included. Despite large differences in environmental conditions, such as N fertilization and geographic location, N₂ fixation (Nfix; kg N per ha and year) was significantly (P<0.001) correlated to legume dry matter yield (DM; kg per ha and year). Very rough, but nevertheless valuable estimations of Nfix in legume/grass mixtures (roots not considered) are given by Nfix = 0.026DM + 7 for T. pratense, Nfix = 0.031DM + 24 for T. repens, and Nfix = 0.021DM + 17 for M. sativa.     

Influence of soil water potential on respiration and nitrogen fixation ofAzotobacter vinelandii

Summary Respiration and N₂-fixation (acetylene reduction) ofAzotobacter vinelandii have been studied at a variety of soil water potentials. Both processes were strictly linked and strongly reduced at water potentials between –0.6 and –1.3 MPa. Complete inhibition occurred below –2.1MPa. Osmotic potentials in soil compared to matric potentials of the same value were less inhibitory to respiration and acetylene reduction by Azotobacter. The N₂-fixing efficiency (mg N/g glucose) was not influenced by water potentials ranging from –0.1 to –2.1 MPa.     

Alteration of cyanobacterial glutamine synthetase activity in vivo in response to light and NH 4 +

Extractable glutamine synthetase activity of the cyanobacterium Anabaena cylindrica was reduced by approximately 50% when N₂-fixing cultures were treated with 10 mM NH ₄ ⁺ or were placed in darkness. The deactivated enzyme could be rapidly reactivated (within 5 min) by adding 40 mM 2-mercaptoethanol to the biosynthetic reaction mixture. The enzyme could also be reactivated in vivo by replacing the culture in light or by removing NH ₄ ⁺ . When the enzyme was deactivated by simultaneously adding NH ₄ ⁺ and placing the culture in darkness, reactivation occurred on reillumination and removal of NH ₄ ⁺ . The removal of NH ₄ ⁺ in darkness did not result in reactivation. On in vitro reactivation of glutamine synthetase from dark or NH ₄ ⁺ -treated cultures the maximum glutamine synthetase activity observed frequently exceeded that of glutamine synthetase extracted from untreated cultures. Anacystis nidulans showed a similar type of reversible dark deactivation to A. cylindrica but Plectonema boryanum and a Nostoc did not. With A. cylindrica, a direct positive correlation between the size of the intracellular pool of glutamate and biosynthetic glutamine synthetase activity occurred during light/dark shifts, and on treatment with NH ₄ ⁺ . The changes in activity of glutamine synthetase in A. cylindrica in response to light resemble in some respects the light modulation of enzymes of the oxidative and reductive pentose phosphate pathways noted in cyanobacteria by others.     

Rhodospirillum centenum,sp. nov., a thermotolerant cyst-forming anoxygenic photosynthetic bacterium

A novel non-sulfur purple photosynthetic bacterium, designated Rhodospirillum centenum, was isolated from an enrichment culture designed to favor growth of anoxygenic photosynthetic N₂-fixing bacteria. R. centenum grows optimally at 40–42° C and has the capacity to produce cytoplasmic R bodies, refractile structures not observed hitherto in photosynthetic prokaryotes. The bacterium is also unusual among photosynthetic bacteria in that it forms desiccation-resistant cysts when grown aerobically in darkness with butyrate as the sole carbon source.     

Carbon cost of nitrogenase activity in Frankia–Alnus incana root nodules

The carbon cost of nitrogenase activity was investigated to determine symbiotic efficiency of the actinorhizal root nodule symbiosis between the woody perennial Alnus incana and the soil bacterium Frankia. Respiration (CO₂ production) and nitrogenase activity (H₂ production) by intact nodulated root systems were continuously recorded in short-term assays in an open-flow gas exchange system. The assays were conducted in N₂:O₂, thus under N₂-fixing conditions, in all experiments except for one. This avoided the declines in nitrogenase activity and respiration due to N₂ deprivation that occur in acetylene reduction assays and during extended Ar:O₂ exposures in H₂ assays. Two approaches were used: (i) direct estimation of root and nodule respiration by removing nodules, and (ii) decreasing the partial pressure of O₂ from 21 to 15% to use the strong relationship between respiration and nitrogenase activity to calculate CO₂/H₂. The electron allocation of nitrogenase was determined to be 0.6 and used to convert the results into moles of CO₂ produced per 2e^– transferred by nitrogenase to reduction of N₂. The results ranged from 2.6 to 3.4mol CO₂ produced per 2e^–. Carbon cost expressed as gC produced per gN reduced ranged from 4.5 to 5.8. The result for this actinorhizal tree symbiosis is in the low range of estimates for N₂-fixing actinorhizal symbioses and crop legumes. Methodology and comparisons of root nodule physiology among actinorhizal and legume plants are discussed.     

Effects of N source on proton excretion,ionic balance and growth ofAlnus glutinosa (L.) Gaertner: comparison of N2 fixation with single and mixed sources of NO3 and NH4

Summary Non-nodulatedalnus glutinosa plants were grown for 6 weeks in nutrient solutions using 3 combined-N treatments (NO₃; NO₃/NH₄; and NH₄) at a total N level of 4 meq.l^–1, and growth was ccmpared with nodulated plants at zero N (N₂ fixation). Of the combined-N sources, 100 per cent NH₄ resulted in the highest dry matter yields when the solution pH was adjusted daily atc. 6. The dry matter yield was lowest with NO₃.During the first 3 weeks, the yield of the N₂-fixing plants was as high as that of the NH₄ plants, but fell relatively behind during the second 3-week period. These effects could be attributed to higher initial N contents and higher shoot:root ratios, respectively, in the N₂-fixing plants. Specific rates of N acquisition in the root were of a comparable order of magnitude for the combined-N and zero-N treatments.When NO₃ was taken up, it was almost completely reduced in the roots. Regardless of N source there was a large excess of cations (C) relative to inorganic anions (A) in the plants, which was presumed to be balanced by an equivalent amount of organic anions (C-A). The relatively small differences in generation of organic anions for the various modes of N supply indicated the relative importance of the proton pump when NH₄ or N₂ was the N source. Proton or hydroxyl-ion effluxes, calculated on the basis of plant analyses, were generally in good agreement with measured excretion values. The acidity generation with N₂ fixation amounted toc. 0.5 meq H⁺.mmol^–1 N_org, which was distinctly higher than the range of 0.1–0.2 mentioned by Raven and Smith⁴³ for dinitrogen-fixing plants.Without pH adjustment, specific rates of cation uptake and carboxylate generation were strongly depressed as the acidity increased, when NO₃/NH₄, NH₄ and N₂ were the N sources. Growth ofAlnus glutinosa appeared to be still normal at a pH ofc. 2.8. During the final 3 weeks, only the NH₄ plants ceased growing at a pH of 2.6.     

Outdoor mass culture ofAzolla spp.: yields and efficiencies of nitrogen fixation

Summary The productivity of three species of Azolla (A. pinnata, A. filiculoides andA. caroliniana) in outdoor culture has been evaluated at different planting densities. The highest yields were obtained with biomass concentration ranging from 40 to 70g d.w. m^–2. The mean productivity over a 90 days period (from May 10th to August 10th) ranged from 10g d.w. m^–2 day^–1 forA. filiculoides up to 11.5 g d.w. m^–2 day^–1 forA. caroliniana. The nitrogen content of the dried biomasses was 48.3 mg (g d.w.)^–1 forA. pinnata, 51.5mg (g d.w.)^–1 forA. filiculoides and 52.3 mg (g d.w.)^–1 forA. caroliniana. Very little variations of the nitrogen content of the ferns during the experimental period were observed.The nitrogen-fixing efficiency of the Azolla-Anabaena azollae symbiosis grown in outdoor conditions was evaluated both by direct measurement of the amount of N₂ fixed by the culture and by the C₂H₂-reduction and H₂-evolution tests in an air atmosphere. These tests were performed outdoor under the same environmental conditions as the growing cultures. For all the species the ratios of C₂H₂-reduced to N₂-fixed were unexpectedly low, ranging from 2.04 (A. pinnata) to 1.50 (A. caroliniana).The results suggest that the reliability of the C₂H₂-reduction assay, particularly when applied to complex biological N₂-fixing systems, must be re-examined.     

Application of glucose at low concentrations to grass swards in waste-derived compost can significantly increase long-term yields

Carbohydrates have a range of effects on soil, dependent on the frequency and concentration of the application. Small quantities of glucose have the effect of accelerating the removal of available N (NH₄ ⁺, NO₃ ^–) through incorporation into the bodies of microorganisms. This reduces plant growth (Jenkinson, 1985), the rate of which depends largely on the presence of available N (Addiscott et al., 1991). However, in theory, if appropriate soil glucose concentrations are maintained, asymbiotic N₂-fixation will occur, supplying extra nitrogen nutrition to plants over an extended period. Here, it is demonstrated that the use of 0.028 M glucose and an appropriate source of N₂-fixing bacteria (green waste-derived compost) can result in increased grass dry matter yields of over 50% in a glasshouse experiment.     

Cell wall and sheath constituents of the cyanobacterium Gloeobacter violaceus

Sheaths isolated from Gloeobacter violaceus were found to be composed of a major polysaccharide moiety (glucose, galactose, rhamnose, mannose, arabinose), a protein moiety, and negatively charged components (glucuronic acids, phosphate, sulfate). Outer membrane polypeptide patterns were dominated by two major peptidoglycan-associated proteins (M_r 62,000 and 53,000). Lipopolysaccharide constituents were glucosamine, 3-hydroxy fatty acids (3-OH-14:0, anteiso-3-OH-15:0, 3-OH-16:0, 3-OH-18:0), carbohydrates, and phosphate. A1-type peptidoglycan and non-peptidoglycan components (mannosamine, glucose, mannose, and glucosamine) indicated the presence of a peptidoglycan-polysaccharide complex in the cell walls of Gloeobacter violaceus.Abbreviations A₂pm diaminopimelic acid - ATCC American Type Culture Collection - CE cell envelope - CM cytoplasmic membrane - CW cell wall - dOcla 3-deoxy-d-manno-2-octulosonic acid - GalN galactosamine - GlcN glucosamine - GlcUA glucuronic acid - HF hydrofluoric acid - LPS lipopolysaccharide - ManN mannosamine - M relative molecular mass - MurN muramic acid - MurN-6-P muramic acid-6-phosphate - OMe O-methyl - PAGE polyacrylamide gel electrophoresis - PCC Pasteur Culture Collection - SDS sodium dodecyl sulfate - SH sheath     

Inoculation of sugar mill by-products compost with N2-fixing bacteria

Inoculation of sugar mill by-products compost with N₂-fixing bacteria may improve its quality by increasing total N and available P. Compost was inoculated with Azotobacter vinelandii(ATCC 478), Beijerinckia derxii (ATCC 49361), and Azospirillumsp. TS8, each alone and all three together. Numbers of all N₂-fixing bacteria in compost declined from an initial population of 5×10⁵cellsg^–1 during incubation. The population of Azotobacter declined to approximately 2×10²cellsg^–1 and the population of Beijerinckia and Azospirillum declined to approximately 9×10³ and 3.5×10⁴cellsg^–1 respectively, at day 50. Inoculation with N₂-fixing bacteria increased acetylene reduction, total N by 6–16 and available P by 25–30% in comparison to the uninoculated control. Increasing the N content and P availability of compost increases its value and there may be additional benefit from providing N₂ fixing bacteria.     

Effect of algalization on seed germination of vegetable crops

Soaking seeds of cucumber and pumpkin with an extract of Westiellopsis prolifica, an N₂-fixing cyanobacterium, promoted germination and their subsequent growth and development. An extract of Lyngbya sp., a non-N₂-fixing cyanobacterium, had no significant effect.The authors are with the Algal Physiology Laboratory, Department of Botany, Berhampur University, Berhampur-760007, Orissa, India.