Maize Growth Promotion by Inoculation with an Engineered Ammonium-Excreting Strain of Nitrogen-Fixing .

Diazotroph mutants designed using metabolic engineering to excrete surplus ammonium were used to enhance nitrogen fixation and plant growth, as the levels of nitrogen fixation attained with diazotrophs are insufficient for the plant's needs. In this study, wild-type (A1501) and engineered ammonium-excreting (1568/pVA3) strains of nitrogen-fixing strains were tested in vitro based on plant growth-promoting traits, such as phosphate solubilization ability, indole acetic acid (IAA) production and nitrogenase activities, as well as ammonium excretion as affected by mannitol-mediated osmotic stress. The maize plant growth-promoting effect of the A1501 and 1568/pVA3 strains was evaluated in pots and in the field, and the N-dilution technique was employed to assess the proportion of plant nitrogen derived from nitrogen fixation.

Effect of light-emitting diodes with different color rendering indexes on the ocular tissues of rat.

Aim: To compare the damage of light-emitting diodes (LEDs) with different color rendering indexes (CRIs) to the ocular surface and retina of rats.

Methods: Totally 20 Sprague-Dawley (SD) rats were randomly divided into four groups: the first group was normal control group without any intervention, other three groups were exposed by LEDs with low (LED-L), medium (LED-M), and high (LED-H) CRI respectively for 12h a day, continuously for 4wk. The changes in tear secretion (Schirmer I test, SIt), tear film break-up time (BUT), and corneal fluorescein sodium staining (CFS) scores were compared at different times (1d before experiment, 2 and 4wk after the experiment).

Post-transcriptional control of bacterial nitrogen metabolism by regulatory noncoding RNAs.

Nitrogen metabolism is the most basic process of material and energy metabolism in living organisms, and processes involving the uptake and use of different nitrogen sources are usually tightly regulated at the transcriptional and post-transcriptional levels. Bacterial regulatory noncoding RNAs are novel post-transcriptional regulators that repress or activate the expression of target genes through complementarily pairing with target mRNAs; therefore, these noncoding RNAs play an important regulatory role in many physiological processes, such as bacterial substance metabolism and stress response. In recent years, a study found that noncoding RNAs play a vital role in the post-transcriptional regulation of nitrogen metabolism, which is currently a hot topic in the study of bacterial nitrogen metabolism regulation.

The Sigma Factor AlgU Regulates Exopolysaccharide Production and Nitrogen-Fixing Biofilm Formation by Directly Activating the Transcription of in A1501.

A1501, a plant-associated diazotrophic bacterium, prefers to conform to a nitrogen-fixing biofilm state under nitrogen-deficient conditions. The extracytoplasmic function (ECF) sigma factor AlgU is reported to play key roles in exopolysaccharide (EPS) production and biofilm formation in the genus; however, the function of AlgU in A1501 is still unclear. In this work, we mainly investigated the role of in EPS production, biofilm formation and nitrogenase activity in A1501.

Shinella oryzae sp. nov., a novel zearalenone-resistant bacterium isolated from rice paddy soil.

A novel bacterium, designated Z-25, was isolated from a rice paddy rhizosphere soil sample from Wuchang County, China. The Z-25 strain is gram-negative, rod-shaped, non-spore-forming, aerobic, motile by unipolar flagella and straw white in color. A phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain Z-25 belongs to the genus Shinella, and the closest members are Shinella zoogloeoides ATCC 19623 with 98.

Master regulator NtrC controls the utilization of alternative nitrogen sources in Pseudomonas stutzeri A1501.

Pseudomonas stutzeri A1501 is a model strain used to study associative nitrogen fixation, and it possesses the nitrogen regulatory NtrC protein in the core genome. Nitrogen sources represent one of the important factors affecting the efficiency of biological nitrogen fixation in the natural environment. However, the regulation of NtrC during nitrogen metabolism in P.

A regulatory network involving Rpo, Gac and Rsm for nitrogen-fixing biofilm formation by Pseudomonas stutzeri.

Biofilm and nitrogen fixation are two competitive strategies used by many plant-associated bacteria; however, the mechanisms underlying the formation of nitrogen-fixing biofilms remain largely unknown. Here, we examined the roles of multiple signalling systems in the regulation of biofilm formation by root-associated diazotrophic P. stutzeri A1501.

sp. nov., isolated from meadow soil.

A novel Gram-stain-positive, yellow, short-rod-shaped or coccoid bacterial strain, W204, was isolated from a soil sample collected from Jiadengyu national forest park in China and characterized using a polyphasic approach. The cell-wall peptidoglycan contained ornithine as the diagnostic diamino acid. 16S rRNA gene sequence analysis indicated that strain W204 was closely related to CPCC 203535 (97.

Isolation and Identification of HR1, a Novel Thermo-Tolerant Bacterium, and Comparative Genomics among Species.

Members of the genus are metabolically versatile and widely distributed in Nature. However, knowledge of the bacteria that belong to this genus is currently limited to biochemical characteristics. Herein, a novel thermo-tolerant bacterium named rg HR1 was isolated and identified.

Effect of inoculation with nitrogen-fixing bacterium Pseudomonas stutzeri A1501 on maize plant growth and the microbiome indigenous to the rhizosphere.

Plant growth promoting diazotrophs with the ability to associate with plant roots are in common use as inoculants to benefit crop yield and to mitigate chemical nitrogen fertilization. However, limited information is available in understanding to what extent the plant growth-promoting effect of the inoculum has on the plant's nitrogen acquisition as well as on the impact of inoculation on the indigenous rhizosphere microbial population. Here we reported on experiments that assessed how endophytic Pseudomonas stutzeri A1501 inoculated on maize improved plant growth and plant nitrogen content using a N dilution technique under two water regime conditions.

High Oxygen Concentration Increases the Abundance and Activity of Bacterial Rather than Archaeal Nitrifiers in Rice Field Soil.

Oxygen is considered as a limiting factor for nitrification in rice paddy soil. However, little is known about how the nitrifying microbial community responds to different oxygen concentrations at community and transcript level. In this study, soil and roots were harvested from 50-day-old rice microcosms and were incubated for up to 45 days under two oxygen concentrations: 2 % O(2) and 20 % O(2) (ambient air).

A copper-responsive gene cluster is required for copper homeostasis and contributes to oxidative resistance in Deinococcus radiodurans R1.

Excess copper is toxic to organisms, and therefore, copper homeostasis is important for the limitation of its cellular levels. However, copper homeostasis has not been studied to date in the bacteria Deinococcus radiodurans R1, which exhibits extreme resistance to various environmental stresses. We have identified a copper-responsive gene cluster that encodes CopA, which is a copper-transporting P1-type ATPase, CopZ, which is a copper metallochaperone, and CsoR, which is a copper-sensing repressor.

Different behaviour of methanogenic archaea and Thaumarchaeota in rice field microcosms.

Archaea in rice fields play an important role in carbon and nitrogen cycling. They comprise methane-producing Euryarchaeota as well as ammonia-oxidizing Thaumarchaeota, but their community structures and population dynamics have not yet been studied in the same system. Different soil compartments (surface, bulk, rhizospheric soil) and ages of roots (young and old roots) at two N fertilization levels and at three time points (the panicle initiation, heading and maturity periods) of the season were assayed by determining the abundance (using qPCR) and composition (using T-RFLP and cloning/sequencing) of archaeal genes (mcrA, amoA, 16S rRNA gene).

Autotrophic growth of bacterial and archaeal ammonia oxidizers in freshwater sediment microcosms incubated at different temperatures.

Both bacteria and archaea potentially contribute to ammonia oxidation, but their roles in freshwater sediments are still poorly understood. Seasonal differences in the relative activities of these groups might exist, since cultivated archaeal ammonia oxidizers have higher temperature optima than their bacterial counterparts. In this study, sediment collected from eutrophic freshwater Lake Taihu (China) was incubated at different temperatures (4°C, 15°C, 25°C, and 37°C) for up to 8 weeks.

Niche differentiation of ammonia oxidizers and nitrite oxidizers in rice paddy soil.

The dynamics of populations and activities of ammonia-oxidizing and nitrite-oxidizing microorganisms were investigated in rice microcosms treated with two levels of nitrogen. Different soil compartments (surface, bulk, rhizospheric soil) and roots (young and old roots) were collected at three time points (the panicle initiation, heading and maturity periods) of the season. The population dynamics of bacterial (AOB) and archaeal (AOA) ammonia oxidizers was assayed by determining the abundance (using qPCR) and composition (using T-RFLP and cloning/sequencing) of their amoA genes (coding for a subunit of ammonia monooxygenase), that of nitrite oxidizers (NOB) by quantifying the nxrA gene (coding for a subunit of nitrite oxidase of Nitrobacter spp.

Adaptation of ammonia-oxidizing microorganisms to environment shift of paddy field soil.

Adaptation of microorganisms to the environment is a central theme in microbial ecology. The objective of this study was to investigate the response of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) to a soil medium shift. We employed two rice field soils collected from Beijing and Hangzhou, China.

Composition of archaeal community in a paddy field as affected by rice cultivar and N fertilizer.

Methanogenesis in paddy fields is significantly influenced by environmental and field management factors such as rice cultivar and nitrogenous fertilizer. However, it has been unclear whether such effects are reflected in the structure of methanogenic archaeal populations. In the present study, molecular analyses including cloning and sequencing and terminal restriction fragment length polymorphism (T-RFLP) fingerprinting of archaeal 16S rRNA genes were used to characterize the methanogenic archaeal assemblages and to identify the effect of environmental variables including rice cultivar and N fertilizer on archaeal community compositions in a Chinese paddy field soil.

Community composition of ammonia-oxidizing bacteria and archaea in rice field soil as affected by nitrogen fertilization.

Little information is available on the ecology of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in flooded rice soils. Consequently, a microcosm experiment was conducted to determine the effect of nitrogen fertilizer on the composition of AOB and AOA communities in rice soil by using molecular analyses of ammonia monooxygenase gene (amoA) fragments. Experimental treatments included three levels of N (urea) fertilizer, i.