Certain Environmental Conditions Maximize Ammonium Accumulation and Minimize Nitrogen Loss During Nitrate Reduction Process by Pseudomonas putida Y-9

Abstract

Realizing the smallest nitrogen loss is a challenge in the nitrate reduction process. Dissimilatory nitrate reduction to ammonium (DNRA) and nitrate assimilation play crucial roles in nitrogen retention. In this study, the effects of the carbon source, C/N ratio, pH, and dissolved oxygen on the multiple nitrate reduction pathways conducted by Pseudomonas putida Y-9 are explored. Strain Y-9 efficiently removed nitrate (up to 89.79%) with glucose as the sole carbon source, and the nitrogen loss in this system was 15.43%. The total nitrogen decrease and ammonium accumulation at a C/N ratio of 9 were lower than that at 12 and higher than that at 15, respectively (P < 0.05). Besides, neutral and alkaline conditions (pH 7–9) favored nitrate reduction. Largest nitrate removal (81.78%) and minimum nitrogen loss (10.63%) were observed at pH 7. The nitrate removal and ammonium production efficiencies of strain Y-9 increased due to an increased shaking speed. The expression patterns of nirBD (the gene that controls nitrate assimilation and DNRA) in strain Y-9 were similar to ammonium patterns of the tested incubation conditions. In summary, the following conditions facilitated nitrate assimilation and DNRA by strain Y-9, while reducing the denitrification: glucose as the carbon source, a C/N ratio of 9, a pH of 7, and a shaking speed of 150 rpm. Under these conditions, nitrate removal was substantial, and nitrogen loss from the system was minimal.

Efficient Mn(II) removal mechanism by Serratia marcescens QZB-1 at high manganese concentration

“…The Mn(II) removal efficiency was at its maximum at 150 rpm and then decreased when the rotating speed was higher than 150 rpm. This might be because the growth of bacteria and the capability to remove the contaminant were inhibited when the content of oxygen exceeded a critical level ( Lei et al, 2019 ; Hou et al, 2021 ; Huang et al, 2021 ). Overall, strain QZB-1 showed a high tolerance against to Mn(II) (up to 364 mM) and could efficiently remove 18 mM of Mn(II) under the following conditions: pH 5.5, 35°C, and 150 rpm.…”

“…In temperature experiments, the temperature was set to 10, 20, 30, 35, or 40°C. In the agitation experiments, the shaking speed was set to 0, 50, 100, 150, or 200 rpm, as per previous studies ( Chen et al, 2021 ; Huang et al, 2021 ; Yan et al, 2021 ). The cultures were incubated for 2 days, and samples were then collected to measure the pH, OD 600 , and Mn(II) concentration.…”

Impact of Species-Specific Plant Growth-Promoting Rhizobacteria (PGPR) on Maize (Zea mays) Phenotypic and Biochemical Diversity

“…PGPR strains B. subtilis and P. putida have shown a more pronounced effect on NR activity as compared to other bacteria under study. Both these bacteria have previously been shown to improve nitrate fascination, allowing plants to make maximum consumption of the nitrogen source (Cervantes-Vázquez et al, 2021;Huang et al, 2021), which advanced to improvement in seedling root development; increase in nitric oxide and auxins contents and hence the result obtained.…”

“…PGPR strains B. subtilis and P. putida have shown a more pronounced effect on NR activity as compared to other bacteria under study. Both these bacteria have previously been shown to improve nitrate fascination, allowing plants to make maximum consumption of the nitrogen source (Cervantes-Vázquez et al, 2021; Huang et al, 2021), which advanced to improvement in seedling root development; increase in nitric oxide and auxins contents and hence the result obtained. According to Lee et al (2020) for plants to adapt to difficult circumstances, nitrate-reducing enzyme activity is crucial, and B. subtilis L1 inoculation results in a significant increase in NR activity, as compared to the genotype that did not receive any bacterial inoculation.…”

The nitrite reductase encoded by nirBDs in Pseudomonas putida Y-9 influences ammonium transformation

“…The PCR cycling conditions were as follows: initial denaturation at 95 • C for 30 s; 38 cycles at 95 • C for 15 s, 60 • C for 30 s, and 72 • C for 30 s; 1 cycle of 95 • C for 15 s; and finally, stepwise temperature increases from 55 to 95 • C to generate the melting curve. Standard curves were established using a dilution series of pMD19-T vectors containing the target gene (Huang et al, 2021b).…”