Secretome Analysis of the Plant Biostimulant Bacteria Strains Bacillus subtilis (EB2004S) and Lactobacillus helveticus (EL2006H) in Response to pH Changes

Interactions of rhizosphere microbiota-environmental factors-pharmacological active ingredients of Eucommia ulmoides

MAIN CONCLUSION

The composition, diversity and co-occurrence patterns of the rhizosphere microbiota of E. ulmoides were significantly influenced by environmental factors, and which were potentially associated with the contents of pharmacological active ingredients. Eucommia ulmoides is an important perennial medicinal plant. However, little is known about the interactions among microbiota, environmental factors (EFs), and pharmacological active ingredients (PAIs) of E. ulmoides. Herein, we analyzed the interactions among rhizosphere microbiota-EFs-PAIs of E. ulmoides by amplicon sequencing and multi-analytical approach. Our results revealed variations in the dominant genera, diversity, and co-occurrence networks of the rhizosphere microbiota of E. ulmoides across different geographical locations. Notably, available nitrogen exerted the strongest influence on fungal dominant genera, while pH significantly impacted bacterial dominant genera. Rainfall and relative humidity exhibited pronounced effects on the α-diversity of fungal groups, whereas available phosphorus influenced the number of nodes in fungal co-occurrence networks. Altitude and total phosphorus had substantial effects on the average degree and nodes in bacterial co-occurrence networks. Furthermore, the dominant genera, diversity and co-occurrence network of rhizosphere microbiota of E. ulmoides were significantly correlated with the content of PAIs. Specifically, the abundance of rhizosphere dominant genera Filobasidium, Hannaella and Nitrospira were significantly correlated with the content of pinoresinol diglucoside (PD). Similarly, the abundance of Vishniacozyma and Bradyrhizobium correlated significantly with the content of geniposidic acid (GC), while the abundance of Gemmatimonas was significantly correlated with the content of aucubin. Moreover, the bacterial co-occurrence network parameters including average degree, density, and edge, were significantly correlated with the content of GC and aucubin. The α-diversity index Chao1 also displayed a significant correlation with the content of PD. These findings contribute to a more comprehensive understanding of the interactions between medicinal plants and microbes.

Comparison of Lactiplantibacillus plantarum isolates from the gut of mice supplemented with different types of nutrients: a genomic and metabolomic study

Many studies have focused on the influence of dietary supplements on gut microbiota composition, but limited research have reported their effects on specific bacterial species in the gut. Lactiplantibacillus plantarum is one of the most widely studied probiotics, with a wide range of sources and good environmental adaptability. In this study, in order to elucidate the adaptation strategies of L. plantarum to the gut of mice supplemented with carbohydrates, peptides and minerals, whole genome resequencing and intracellular metabolites detection were performed, and high-frequency mutant genes and differential metabolites were screened. The results suggested different types of dietary supplements do have different effects on L. plantarum from the gut of mice. Additionally, KEGG annotation unveiled that the effects of these dietary supplements on the gene level of L. plantarum primarily pertained to environmental information processing, while the differential metabolites were predominantly associated with metabolism. This study provided new perspectives on the adaptive mechanism of L. plantarum in response to the host's gut environment, suggesting that the diversity of the genome and metabolome of L. plantarum was correlated with dietary supplements. Furthermore, this study offered useful guidance in the effective utilization of dietary supplements.

Effect of NaCl stress on exoproteome profiles of Bacillus amyloliquefaciens EB2003A and Lactobacillus helveticus EL2006H

Salt stress can affect survival, multiplication and ability of plant growth promoting microorganisms to enhance plant growth. Changes in a microbe's proteome profile is one of the mechanisms employed by PGPM to enhance tolerance of salt stress. This study was focused on understanding changes in the exoproteome profile of Bacillus amyloliquefaciens EB2003A and Lactobacillus helveticus EL2006H when exposed to salt stress. The strains were cultured in 100 mL M13 (B. amyloliquefaciens) and 100 mL De man, Rogosa and Sharpe (MRS) (L. helveticus) media, supplemented with 200 and 0 mM NaCl (control), at pH 7.0. The strains were then incubated for 48 h (late exponential growth phase), at 120 rpm and 30 (B. amyloliquefaciens) and 37 (L. helveticus) °C. The microbial cultures were then centrifuged and filtered sterilized, to obtain cell free supernatants whose proteome profiles were studied using LC-MS/MS analysis and quantified using scaffold. Results of the study revealed that treatment with 200 mM NaCl negatively affected the quantity of identified proteins in comparison to the control, for both strains. There was upregulation and downregulation of some proteins, even up to 100%, which resulted in identification of proteins significantly unique between the control or 200 mM NaCl (p ≤ 0.05), for both microbial species. Proteins unique to 200 mM NaCl were mostly those involved in cell wall metabolism, substrate transport, oxidative stress tolerance, gene expression and DNA replication and repair. Some of the identified unique proteins have also been reported to enhance plant growth. In conclusion, based on the results of the work described here, PGPM alter their exoproteome profile when exposed to salt stress, potentially upregulating proteins that enhance their tolerance to this stress.

Cell-Free Supernatant (CFS) from Bacillus subtilis EB2004S and Lactobacillus helveticus EL2006H Cultured at a Range of pH Levels Modulates Potato Plant Growth under Greenhouse Conditions

Agriculture involving industrial fertilizers is another major human made contributing factor to soil pH variation after natural factors such as soil parent rock, weathering time span, climate, and vegetation. The current study assessed the potential effect of cell-free supernatant (CFS) obtained from Bacillus subtilis EB2004S and Lactobacillus helveticus EL2006H cultured at three pH levels (5, 7, and 8) on potato (var Goldrush) growth enhancement in a greenhouse pot experiment. The results showed that CFSs obtained from B. subtilis EB2004S and L. helveticus EL2006H cultured at pH 5 significantly improved photosynthetic rates, stomatal conductance, root fresh weight, and whole plant fresh weight. interactive effects of pot pH and that of CFSs obtained from pH 5 influenced chlorophyll, plant height, and shoot and whole plant fresh weight. Moreover, treatment 52EB2004S~0.4% initiated early tuberization for potato grown at pH 7 and 8. Potato grown at pH 5, which received a 72EB2004S~0.4% CFS treatment, had greater whole plant fresh and dry weight than that treated with L. helveticus EL2006H CFS and a positive control. Taken together, the findings of this study are unique in that it probed the effect of CFS produced under differing pH conditions which revealed a new possibility to mitigate stresses in plants.