Arbuscular mycorrhizal fungi increased peanut (Arachis hypogaea L.) yield by changing the rhizosphere microbial community structure in saline-alkali soil

Arbuscular mycorrhizal fungi (AMF) have demonstrated the potential to enhance the saline-alkali tolerance in plants. Nevertheless, the extent to which AMF can ameliorate the tolerance of salt-sensitive plants to alkaline conditions necessitates further investigation. The current study is primarily centered on elucidating the impact of AMF on the growth of the Huayu22 (H22) when cultivated in saline-alkaline soil. We leveraged DNA of rhizosphere microorganisms extracted from saline-alkali soil subjected to AMF treatment and conducted high-throughput sequencing encompassing 16S rRNA gene and ITS sequencing. Our findings from high-throughput sequencing unveiled Proteobacteria and Bacillus as the prevailing phylum and genus within the bacterial population, respectively. Likewise, the predominant fungal phylum and genus were identified as Ascomycota and Haematonectria. It is noteworthy that the relative abundance of Proteobacteria, Actinobacteria, Chloroflexi, Bacteroidetes, and Ascomycota exhibited significant increments subsequent to AMF inoculation. Our investigation into soil enzyme activity revealed a remarkable surge post-AMF inoculation. Notably, the amounts of pathogen growth inhibitory enzymes and organic carbon degrading enzymes rise, as predicted by the putative roles of microbial communities. In saline-alkali soil, inoculation of AMF did boost the yield of H22. Notable improvements were observed in the weight of both 100 fruits and 100 grains, which increased by 20.02% and 22.30%, respectively. Conclusively, this study not only provides a theoretical framework but also furnishes empirical evidence supporting the utilization of AMF as a viable strategy for augmenting the yield of salt-sensitive plants grown in alkaline conditions

3<i>L</i>, Three-<i>Lactobacilli</i> on Recovering of Microbiome and Immune-Damage by Cyclophosphamide Chemotherapy—A Pilot Experiment in Rats

We deal with various strains of Lactobacillus that can maintain the intestinal microbiome of rats treated with cyclophosphamide, an anticancer agent (chemotherapy). We use MiSeq and various types of statistical tests to prove that cyclophosphamide in rats alters the intestinal microbiome, favoring the growth of various fungi that are extremely harmful to intestinal metabolism. On the contrary, when Lactobacillus 3L is administered together with cyclophosphamide, we prove that the microbiome is preserved by having a much better intestinal metabolism

A comprehensive alanine-scanning mutagenesis study reveals roles for salt bridges in the structure and activity of Pseudomonas aeruginosa elastase.

The relationship between salt bridges and stability/enzymatic activity is unclear. We studied this relationship by systematic alanine-scanning mutation analysis using the typical M4 family metalloprotease Pseudomonas aeruginosa elastase (PAE, also known as pseudolysin) as a model. Structural analysis revealed seven salt bridges in the PAE structure. We constructed ten mutants for six salt bridges. Among these mutants, six (Asp189Ala, Arg179Ala, Asp201Ala, Arg205Ala, Arg245Ala and Glu249Ala) were active and four (Asp168Ala, Arg198Ala, Arg253Ala, and Arg279Ala) were inactive. Five mutants were purified, and their catalytic efficiencies (kcat/Km), half-lives (t1/2) and thermal unfolding curves were compared with those of PAE. Mutants Asp189Ala and Arg179Ala both showed decreased thermal stabilities and increased activities, suggesting that the salt bridge Asp189-Arg179 stabilizes the protein at the expense of catalytic efficiency. In contrast, mutants Asp201Ala and Arg205Ala both showed slightly increased thermal stability and slightly decreased activity, suggesting that the salt bridge Asp201-Arg205 destabilizes the protein. Mutant Glu249Ala is related to a C-terminal salt bridge network and showed both decreased thermal stability and decreased activity. Furthermore, Glu249Ala showed a thermal unfolding curve with three discernable states [the native state (N), the partially unfolded state (I) and the unfolded state (U)]. In comparison, there were only two discernable states (N and U) in the thermal unfolding curve of PAE. These results suggest that Glu249 is important for catalytic efficiency, stability and unfolding cooperativity. This study represents a systematic mutational analyses of salt bridges in the model metalloprotease PAE and provides important insights into the structure-function relationship of enzymes

Thermal inactivation of PAE and the active mutants at 60°C.

<p>The half-life <i>t</i>_1/2 was calculated by linear fitting using equation ln (<i>A</i>/<i>A</i>₀) = -0.693/<i>t</i>_1/2 * <i>t</i>. The vertical axis shows the natural logarithm of the residual activity [ln (<i>A</i>/<i>A</i>₀)]. The half-life <i>t</i>_1/2 corresponds to the point (<i>t</i>_1/2, -0.693) on the fitted line.</p

Specific constant <i>k</i>_cat/<i>K</i>_m values of PAE and the active mutants.

<p>The <i>k</i>_cat/<i>K</i>_m values were measured at 25°C with FAGLA as the substrate. Mutant Arg179Ala was purified after a 12-h incubation. The other mutants were purified after a 2-h incubation. Each measurement was repeated three times, and all of the standard deviations were within 5% of the corresponding mean values.</p

Thermal unfolding of PAE and the active mutants.

<p>The dashed line indicates an unfolded fraction of 0.5.</p

Primers used for site-directed mutagenesis.

<p>Primers used for site-directed mutagenesis.</p

SDS-PAGE analysis of supernatants incubated for maturation (A) and precipitates (B) after ultrasonication.

<p>For PAE and all mutants, the same purification and maturation procedure (with the exception of different incubation times, 2 h or 12 h) were applied, and the same amounts (in volume) of the samples were loaded into different lanes of the SDS-PAGE.</p