The study aimed at screening and identifying a potential poly-β-hydroxybutyrate (PHB) accumulating Bacillus strain and optimization of media parameters for increased PHB production by the strain. A Gram-positive bacterium that accumulated PHB was isolated from local garden soil of Bangalore. Based on morphological and physiological properties, and nucleotide sequence (about 1.5 kb) of its 16S rDNA it was identified as Bacillus thuringiensis IAM 12077. PHB production was found to be comparable to most of the Bacillus sp. reported to date. PHB production by this strain was dependent on nutrient limitation. Cell dry weight and PHB accumulation increased significantly under biphasic growth condition (from nutrient broth to nitrogen-deficient medium) as compared with growth in nutrient broth alone (from 0.32 g/l to 2.76 g/l cell dry weight; 24% to 43.37% PHB accumulation; 0.2 g/l to 1.2 g/l PHB production), with maximum accumulation at 24 h in nitrogen-deficient medium. Time course study of growth and PHB production by this strain in the nitrogen deficient medium showed that PHB production was associated with the stationary phase of growth. All the tested media containing different carbon and nitrogen sources supported growth and PHB production. Ultraviolet spectrum of the extracted polymer showed a characteristic peak at 235 nm.
Biological nitrogen fixation (BNF) is the process that provides organic nitrogenous compounds to the plants by using molecular nitrogen in atmosphere. Higher plants are not capable to use molecular nitrogen in atmosphere as a nitrogen source to generate essential proteins. Therefore plants either should be fertilized by adequate nitrogenous fertilizers or the microorganisms which are capable to produce nitrogenase should provide nitrogen to the plants by BNF. From among a number of factors affecting BNF, soil moisture content and ambient temperatures are considerably effective on the fixation rate. Therefore the global warming would be dramatically defective on BNF, thus effects of soil moisture as well as soil and ambient temperatures on BNF should evaluate prior rising temperature. A pot experiment was carried out to determine the effects of soil water contents on BNF. Four different soil water contents (%25, %50, %75 and %100 of water holding capacity) were adjusted either every 3 days or just after plants indicate wilting point. Non-inoculated pots were added to experiment as a control. The results revealed that BNF is affected by different level of soil water content. The mechanism of this effect would not be the direct effect of water, but the side effect of water on soil oxygen content; therefore, an aeration capability.
The aim of the research was to determine changes in the chemical composition in lupin seeds during seed germination in a solution containing selected nitrogen compounds. Blue lupin seeds of the Neptun cultivar were germinated for 3 or 4 days in darkness, at 24°C in 1% solutions containing the following nitrogen compounds: urea, nitric acid, ammonium sulphate, methionine or yeast extract. The control consisted of seeds germinated in water. The presence of all nitrogen sources has resulted in a poorer growth of the sprouts as compared to seeds germinated in water. There was a significant increase in the true protein content as well as a significant decrease in the content of crude ash and alkaloids in the germinated seeds. The seeds germinated for 4 days had significantly higher total protein content and significantly lower content of nitrogen-free extract compounds and oligosaccharides as compared to the seeds germinated for 3 days. A significant influence of the nitrogen source on the concentration of some amino acids was found. Cystine was found to be absent in seeds germinated in the nitric acid solution, while there occurred a twofold increase in the cystine content and a fivefold increase in the methionine content in seeds germinated in the aqueous solution of methionine and an 50% increase in the cystine concentration was observed in seeds germinated in the yeast extract and ammonium sulphate solution. Methionine and cystine were the limiting amino acids in all the samples, accept of seeds germinated in the methionine solution were it was valine. Aqueous solutions of ammonium sulphate and yeast extract were found to have the most advantageous influence on the chemical composition of lupin germination products.
Effects of mesotrophic lake water enrichment with organic phosphorus and nitrogen substrates (DNA and model protein, bovine serum albumin - BSA) on dynamics and diversity of natural microbial communities (bacteria, heterotrophic nanoflagellates, ciliates) were studied in mesocosm experiments. Simultaneous enrichment with DNA and BSA strongly increased the abundance and biomass of all studied groups of microorganisms and induced changes in their morphological and taxonomic structure. The increased participation of large heterotrophic nanoflagellates cells (larger than 10 μm) in their total numbers and shifts in taxonomic and trophic Structure of the ciliates, from algivorous to small bacterivorous, species were observed. Grazing caused changes in bacterial size distribution in all enriched mesocosms. Large (10-50 μm) filamentous bacteria significantly contributed to the total bacterial numbers and biomass. Pronounced increase in populations of (β- and γ-Proteobacteria was found in lake water enriched with organic P and N sources, whereas α-Pmteobacteria did not change markedly in the studied mesocosms. DNA additions stimulated the rates of bacterial secondary production. BSA shortened the rates of bacterial biomass turnover in lake water. Relatively high and constant (~ 30%) percentage contribution of active bacteria (MEM+) in two mesocosms enriched with DNA and DNA+BSA suggested the important role of nucleic acids as a source of phosphorus for bacterial growth, activity and production. Numerous and statistically significant correlations between bacteria and protists indicated the direct and selective predator-prey relationship.
Sludge of two different ages (3 years old; Type 1 sludge, and 3 months old; Type 2 sludge) were applied to the following soil types: two luvisols, an arenosol and a vertisol at different rates to determine whether sludge application had any effect on the partitioning and consequently, bioavailability and mobility of Cu, Pb and Zn. A five- stage sequential extraction procedure was used to determine the concentration of metals in the different fractions of the soil after sampling and three months after sludge application. Type 1 sludge had higher values for Cu, Pb, and Zn (115.9, 295.5 and 400 mg kg⁻¹, respectively) than Type 2 sludge (110.8, 228.6 and 341 mg kg⁻¹ respectively). These values were significantly higher than values for the background concentrations of the heavy metals in the different soils. Pseudo-total concentration of Cu, Pb and Zn in the soils therefore increased with increase in sludge application rate. Mobility and bioavailability of Cu, Pb, and Zn were affected by interactions between sludge application rate and soil type with sludge age having no significant effect. Some precaution should be taken when the period between sludge application and planting is relatively short to minimize heavy metal mobility and bioavailability.
Girdling was applied to 5-year-old potted beech individuals of early, intermediate and late phenological forms to block assimilate export from leaves. Phloem severance caused accumulation of soluble carbohydrates and starch in leaves and increased the C/N ratio. While the hexose content increased continuously until the end of the experiment, the sucrose and starch contents peaked earlier, depending on the plant’s phenological features. Different rates of chlorophyll degradation and H2O2 and TBARS (thiobarbituric acid-reactive substances) production in different phenological forms implied that phloem girdling was the source of oxidative stress and, depending on the phenological form, accelerated leaf senescence to different degrees. The variable rate of the increase in soluble carbohydrate and starch content, characteristic of the different phenological forms, had different modifying effects on the antioxidant activity in leaves. Compared with the early phenological form, the late form was characterized by a smaller increase in H2O2 and TBARS content and delayed and slowed chlorophyll and carotenoid degradation. In conjunction with the larger increase in the activity of antioxidant enzymes (catalase, ascorbate peroxidase and superoxide dismutase) induced by carbohydrate accumulation and slower carotenoid degradation, these changes led to the late form having greater resistance to oxidative stress and slower senescence.
Cytological studies of Daucus carota L. (cv. Karo) in suspension culture were made. Cells growing on medium without ammonium were larger and more vacuolated than were cells grown on the standard medium. Their sizes (cell area) ranged widely from 200 µrm2 to 40000 µm2. They also showed a very low level of aggregation (1%) as compared to an 81% frequency of aggregates in the standard suspension. Suspension deficient in ammonium had a .small percentage of 2-9-nucleated cells. Such multlnucleate cells were not observed in suspension with both nitrate and ammonium used as nitrogen source.