Respons Hasil Padi dan Hara Tanah Sawah terhadap Bakteri Pelarut Fosfat dan Pemfiksasi Nitrogen

The condition of unfertile paddy field due to excessive inorganic fertilizer application causing soil degradation. Fertilizing techniques using phosphate solubilizing and nitrogen fixer bacteria are breakthroughs that should be developed in paddy cultivation to increase fertility soil and harvest of rice. This research aims to study on phosphate solubilizing and nitrogen fixer bacteria ability to increase the harvest of rice by increasing chemical and biological fertility of soil. The research was conducted in the greenhouse of Sawah Baru experimental garden, IPB University. The design used was a completely randomized design with one factor that was dosage of inorganic fertilizers (NPK) with seven levels that were control, NPK 100%, NPK 0% + bacteria, NPK 25% + bacteria, NPK 50% + bacteria, NPK 75% + bacteria and NPK 100% + bacteria. Each stage was repeated four times, so there were 28 units. The results of phosphate solubilizing and nitrogen fixer bacteria could produce more rice grain 0.32 ton.ha^-1 than NPK 100% (recommended dose). Biological soil fertility improved with the increased population of bacteria, but there was no improved soil chemical fertility of soil.

Mechanisms and heterogeneity of in situ mineral processing by the marine nitrogen fixer Trichodesmium revealed by single-colony metaproteomics

The keystone marine nitrogen fixer Trichodesmium thrives in high-dust environments. While laboratory investigations have observed that Trichodesmium colonies can access the essential nutrient iron from dust particles, less clear are the biochemical strategies underlying particle–colony interactions in nature. Here we demonstrate that Trichodesmium colonies engage with mineral particles in the wild with distinct molecular responses. We encountered particle-laden Trichodesmium colonies at a sampling location in the Southern Caribbean Sea; microscopy and synchrotron-based imaging then demonstrated heterogeneous associations with iron oxide and iron-silicate minerals. Metaproteomic analysis of individual colonies by a new low-biomass approach revealed responses in biogeochemically relevant proteins including photosynthesis proteins and metalloproteins containing iron, nickel, copper, and zinc. The iron-storage protein ferritin was particularly enriched implying accumulation of mineral-derived iron, and multiple iron acquisition pathways including Fe(II), Fe(III), and Fe-siderophore transporters were engaged. While the particles provided key trace metals such as iron and nickel, there was also evidence that Trichodesmium was altering its strategy to confront increased superoxide production and metal exposure. Chemotaxis regulators also responded to mineral presence suggesting involvement in particle entrainment. These molecular responses are fundamental to Trichodesmium’s ecological success and global biogeochemical impact, and may contribute to the leaching of particulate trace metals with implications for global iron and carbon cycling.

Warming Iron-Limited Oceans Enhance Nitrogen Fixation and Drive Biogeographic Specialization of the Globally Important Cyanobacterium Crocosphaera

Primary productivity in the nutrient-poor subtropical ocean gyres depends on new nitrogen inputs from nitrogen fixers that convert inert dinitrogen gas into bioavailable forms. Temperature and iron (Fe) availability constrain marine nitrogen fixation, and both are changing due to anthropogenic ocean warming. We examined the physiological responses of the globally important marine nitrogen fixer, Crocosphaera watsonii across its full thermal range as a function of iron availability. At the lower end of its thermal range, from 22 to 27°C, Crocosphaera growth, nitrogen fixation, and Nitrogen-specific Iron Use Efficiencies (N-IUEs, mol N fixed hour–1 mol Fe–1) increased with temperature. At an optimal growth temperature of 27°C, N-IUEs were 66% higher under iron-limited conditions than iron-replete conditions, indicating that low-iron availability increases metabolic efficiency. However, Crocosphaera growth and function decrease from 27 to 32°C, temperatures that are predicted for an increasing fraction of tropical oceans in the future. Altogether, this suggests that Crocosphaera are well adapted to iron-limited, warm waters, within prescribed limits. A model incorporating these results under the IPCC RCP 8.5 warming scenario predicts that Crocosphaera N-IUEs could increase by a net 47% by 2100, particularly in higher-latitude waters. These results contrast with published responses of another dominant nitrogen fixer (Trichodesmium), with predicted N-IUEs that increase most in low-latitude, tropical waters. These models project that differing responses of Crocosphaera and Trichodesmium N-IUEs to future warming of iron-limited oceans could enhance their current contributions to global marine nitrogen fixation with rates increasing by ∼91 and ∼22%, respectively, thereby shifting their relative importance to marine new production and also intensifying their regional divergence. Thus, interactive temperature and iron effects may profoundly transform existing paradigms of nitrogen biogeochemistry and primary productivity in open ocean regimes.

Prevalence of bacteriocinogenic Rhizobium spp. in mungbean (Vigna radiata)

The present work was undertaken to ascertain prevalence of bacteriocinogenic Rhizobium spp. in mungbean (Vigna radiata). Samples of rhizospheric soil and nodules were plated onto CRYEMA medium, selective for Rhizobium spp. From among the isolates obtained only four, designated as-N8, S1, S6, and S13 demonstrated bacteriocin production. Upto 104 AU/ml (Arbitrary Units/ml) of partially purified bacteriocin (PPB) was detected from N8 and S6. PPB obtained from N8 and S13 exhibited antagonism against indicator strain over a wide range of pH. All isolates of PPB were thermo-stable after heating to 90ºC for 5 minutes. N8 exhibited 14.2mm zone of inhibition after heating to 50ºC for 10 min. It decreased by 29.5% to 10mm (80ºC/ 10min). S6 exhibited zone of inhibition of 11mm (50ºC/10min) which decreased by 18.1% to 9mm (80ºC/10min). Dual inoculation of nitrogen fixing Rhizobium with bacteriocin producing Rhizobium can ensure greater benefit than using nitrogen fixer alone.