Controls on the epilimnetic phosphorus concentration in small temperate lakes

Phosphorus (P) is one of the key limiting nutrients for algal growth in most fresh surface waters. Understanding the determinants of P accumulation in the water column of lakes of...

Effects on Nitrogen and Phosphorus in Agricultural Soils Following the Application of Slurry Amended with Additives

This poster elucidates the experiments related to the first objective of a PhD focussed on the use of amended organic fertilisers (manures/slurries) in agricultural soils. Nitrogen (N) and phosphorus (P) are the most yield-limiting nutrients in many soils. Manures and slurries could represent valid alternatives to inorganic fertilisers to replenish nutrient offtake via harvested crops. Inoculation of slurry using additives, such as Slurrybugs™ and Slurrybooster™, can enhance the nutrient value of slurry, due to the action of microorganism and enzymes within the additives.

Diagnosis and Recommendation Integrated System (DRIS) Norms for Identifying Yield Limiting Nutrients in Byadgi Chilli Fruits Grown in Northern Transitional Zone and Dry Zones of Karnataka (India)

Fruit samples collected from different part of northern Karnataka districts of Dharwad, Gadag and Haveri, when peak fruit harvesting stage were collected the samples, were processed and analysed for various nutrients and thus, the data bank was established. By using Diagnosis and Recommendation Integrated System (DRIS), nutrient expressions, which have shown higher variance and lower coefficient of variation, were selected as norms viz, N/P(4.98), N/K (0.73), N/Ca (1.17), N/Mg (4.65), S/N(0.10), N/Fe(0.02), N/Zn(0.08) etc. In addition, five nutrient ranges have been derived using mean and standard deviation as low, deficient, optimum, high and excess for each nutrient to serve as a guide for diagnostic purpose. The optimum N ranged from 2.30 to 2.84%, P from 0.48 to 0.56%, K from 3.16 to 3.44%, Ca from 2.08 to 2.74%, Mg from 0.60 to 0.88% and S from 0.24 to 0.27%. Among the micronutrients, the optimum Zn ranged from 28.71 to 29.78 ppm, Fe from 113.60 to 150.03 ppm for byadgi chilli crop.

Prochlorococcus exudate stimulates heterotrophic bacterial competition with rival phytoplankton for available nitrogen

The marine cyanobacterium Prochlorococcus numerically dominates the phytoplankton community of the nutrient-limited open ocean, establishing itself as the most abundant photosynthetic organism on Earth. This ecological success has been attributed to lower cell quotas for limiting nutrients, superior resource acquisition, and other advantages associated with cell size reduction and genome streamlining. In this study we tested the prediction that Prochlorococcus outcompetes its rivals for scarce nutrients, and that this advantage leads to its numerical success in nutrient-limited waters. Strains of Prochlorococcus and its sister genus Synechococcus grew well in both mono- and co-culture when nutrients were replete. However, in nitrogen-limited medium Prochlorococcus outgrew Synechococcus, but only when heterotrophic bacteria were also present. In the nitrogen-limited medium, the heterotroph Alteromonas macleodii outcompeted Synechococcus for nitrogen, but only if stimulated by exudate released by Prochlorococcus, or if a proxy organic carbon source was provided. Analysis of a nitrate reductase mutant Alteromonas suggested that Alteromonas outcompetes Synechococcus for nitrate, during which co-cultured Prochlorococcus grows on ammonia or other available nitrogen species. We propose that Prochlorococcus can stimulate antagonism between heterotrophic bacteria and potential phytoplankton competitors through a metabolic cross-feeding interaction, and this stimulation could contribute to the numerical success of Prochlorococcus in the nutrient-limited regions of the ocean.

Study of Oenological Fermentation: Which Strategy and Which Tools?

Wine fermentation is a specific and complex research subject and its control is essential to ensure full process completion while improving wine quality. It displays several specificities, in particular, (i) musts with a very high sugar content, low pH, and some limiting nutrients, as well as a great variability in must composition according to the year, grape variety, and so on; (ii) atypical fermentation conditions with non-isothermal temperature profiles, a quasi-anaerobiosis and legal constraints with a limited and predefined list of authorized operations. New challenges have emerged, related to the increasing diversity of commercially available yeast strains; the fluctuating composition of musts, particularly owing to climate change; and sustainability, which has become a key issue. This paper synthesizes approaches implemented to address all these issues. It details the example of our laboratory that, for many years, has been developing an integrated approach to study yeast diversity, understand their metabolism, and develop new fermentation control strategies. This approach requires the development of specific fermentation devices to study yeast metabolism in a controlled environment that mimics practical conditions and to develop original fermentation control strategies. All these tools are described here, together with their role in the overall scientific strategy and complementary approaches in the literature.

Monoaromatic Hydrocarbon Bioremediation of Hydrocarbon-contaminated Soil Using HBB5 Biosurfactant Produced by Pseudomonas xiamenensis

Biodegradation of benzene toluene ethylbenzene and xylenes (BTEX) is a slow and complex process. However, many microbial organisms have been shown to possess the capacity to biodegrade various components of a hydrocarbon. This study was aimed at investigating the role of biosurfactant on soil polluted with these monoaromatics. Samples were collected and analyzed using standard techniques. The biodegradation set up was carried out using five earthen pots; each containing unpolluted soil, polluted soil alone, polluted soil + poultry wastes, polluted soil + HBB5 biosurfactant and polluted soil + poultry wastes + HBB5 biosurfactant. The biodegradation of BTEX were periodically monitored every seven days for 28 days using gas chromatograph-mass spectrometer coupled with head space (GC-MS-HS). The respective initial and final concentrations of BTEX (ppm) were as follows; 0.7936 and 0.2063, 0.9733 and 0.0231, 0.9526 and <0.0001, 0.9241 and <0.0001 with degradation efficiencies of 74.0%, 97.6%, 100% and 100% for polluted soil alone, polluted soil + poultry wastes, polluted soil + HBB5 biosurfactant and polluted soil + poultry wastes + HBB5 biosurfactant respectively. The microbial counts increased greatly, and the concentrations of the limiting nutrients reduced during the experimental period. The effective treatments for bioremediation increased in the following order: polluted soil alone < polluted soil + poultry waste < polluted soil + HBB5 biosurfactant < polluted soil + poultry waste + HBB5 biosurfactant. Results clearly showed that application of HBB5 biosurfactant only or in combination with poultry wastes has the ability to degrade ethylbenzene and xylenes (BTEX) and thus, can be employed in the clean-up of crude oil contaminated soil.

Use of Limiting Nutrients for Reclamation of Non-responsive Soils in Northern Ghana

A better understanding of soil fertility factors that constraint positive crop response to fertilizer inputs will facilitate the improvement of soil nutrient management. In this study, a nutrient omission trial was carried out in a greenhouse condition to identify soil chemical properties limiting in non-responsive soils and to ascertain their effect on soybean (Glycine max) production. The treatments evaluated were control (distilled water), complete nutrient solution (all nutrients), and complete solution with the omission of each of N, P, K, Ca, Mg, and S and micronutrients (Fe, Zn, Cu, Mn, B, and Mo) arranged in a completely randomized design with three replications. After the greenhouse study, the identified limiting nutrients were tested with or without FertiSoil (commercial compost) in a 3 year field experiment. Results of the soil analyses showed low fertility status of the non-responsive soils. The sufficiency quotient index revealed non-responsive soils in all the sites to be predominantly limiting in P and K. The occurrence of other limiting nutrients was also identified: Pishegu (Zn, B), Serekpere (Mg, S), Daffiama Saapare (Ca, Mg, S), and Naaga (Mg, S, Zn, B). The nutrient inputs positively influenced soybean yield response in all the locations. The application of PKZnB with FertiSoil and FertiSoil alone significantly increased soybean grain yields by 585 and 477 kg ha−1, respectively, at Pishegu. Soybean grain yields also increased by 585, 573, and 364 kg ha−1 under the FertiSoil, PKMgS + FertiSoil, and PKMgS applications at Serekpere, respectively. At Daffiama Saapare, the highest (103%) percent increase in soybean grain yield was recorded from the combined application of PKMgSCa and FertiSoil. However, the application of FertiSoil and PKMgSCa singly equally increased soybean grain yield by 77%. Percent soybean grain yield increases of 86, 84, and 74% were observed when PKMgSZnB + FertiSoil, PKMgSZnB, and FertiSoil were applied, respectively, at Naaga. In absolute terms, 83% of the fields had a positive response to mineral fertilizer and 93% to FertiSoil and mineral fertilizer + FertiSoil applications. Organic amendment and/or site-specific fertilizer applications are the best options for alleviating poor or no crop responses to inputs and improve productivity on non-responsive soils.

The Burkholderia pseudomallei hmqA-G Locus Mediates Competitive Fitness against Environmental Gram-Positive Bacteria

Burkholderia pseudomallei naturally resides in water, soil, and the rhizosphere and its success as an opportunistic pathogen is dependent on the ability to persist in these harsh habitats long enough to come into contact with a susceptible host. In addition to adapting to limiting nutrients and diverse chemical and physical challenges, B. pseudomallei also has to interact with a variety of microbial competitors.