Investigation of bioactivity of unsaturated oligo­galacturonic acids produced from apple waste by Alcaligenes faecalis AGS3 and Paenibacillus polymyxa S4 Pectinases.

Pectin is one of the main structural components in fruits and an indigestible fiber made of D-galacturonic acid units with α (1-4) linkage. This study investigates the microbial degradation of pectin in apple waste and the production of bioactive compounds. Firstly, pectin-degrading bacteria were isolated and identified, then pectinolytic activity was assessed by DNS. The products were evaluated by TLC and LC-MS-ESI. The antioxidative effects were investigated using DPPH and anti-cancer effects and cytotoxicity were analyzed by MTT and flow cytometry. In this study two new bacterial isolates, Alcaligenes faecalis AGS3 and Paenibacillus polymyxa S4 with the pectinolytic enzyme were introduced. Structure analysis showed that the products of enzymatic degradation include unsaturated mono, di, tri, and penta galacturonic acids with 74% and 69% RSA at 40 mg/mL for A. faecalis and P. polymyxa S4, respectively. The results of anti-tumor properties on MCF-7 cells by MTT assay, for products of AGS3 and S4 at 40 mg/mL after 48 h, showed 7% and 9% survival, respectively. In the flow cytometric assessment, the compounds of AGS3 at 40 mg/mL were 100% lethal in 48 h and regarding S4 isolate caused 98% death. Cytotoxicity evaluation on L-929 cells showed no significant toxicity on living cells.

The Serine Biosynthesis of Paenibacillus polymyxa WLY78 Is Regulated by the T-Box Riboswitch.

Serine is important for nearly all microorganisms in protein and downstream amino acids synthesis, however, the effect of serine on growth and nitrogen fixation was not completely clear in many bacteria, besides, the regulatory mode of serine remains to be fully established. In this study, we demonstrated that L-serine is essential for growth and nitrogen fixation of Paenibacillus polymyxa WLY78, but high concentrations of L-serine inhibit growth, nitrogenase activity, and nifH expression. Then, we revealed that expression of the serA whose gene product catalyzes the first reaction in the serine biosynthetic pathway is regulated by the T-box riboswitch regulatory system. The 508 bp mRNA leader region upstream of the serA coding region contains a 280 bp T-box riboswitch. The secondary structure of the T-box riboswitch with several conserved features: three stem-loop structures, a 14-bp T-box sequence, and an intrinsic transcriptional terminator, is predicted. Mutation and the transcriptional leader-lacZ fusions experiments revealed that the specifier codon of serine is AGC (complementary to the anticodon sequence of tRNAser). qRT-PCR showed that transcription of serA is induced by serine starvation, whereas deletion of the specifier codon resulted in nearly no expression of serA. Deletion of the terminator sequence or mutation of the continuous seven T following the terminator led to constitutive expression of serA. The data indicated that the T-box riboswitch, a noncoding RNA segment in the leader region, regulates expression of serA by a transcription antitermination mechanism.

Integrated use of phosphate-solubilizing Bacillus subtilis strain IA6 and zinc-solubilizing Bacillus sp. strain IA16: a promising approach for improving cotton growth.

Mineral nutrition of crop plants is one of the major challenges faced by modern agriculture, particularly in arid and semi-arid regions. In alkaline calcareous soils, the availability of phosphorus and zinc is critically less due to their fixation and precipitation as complexes. Farmers use fertilizers to fulfill crop requirements, but their efficacy is less, which increases production costs. Plant growth-promoting rhizobacteria (PGPR) can improve the availability of crop nutrients through solubilizing the insoluble compounds of phosphorus and zinc in soil. In the present study, a total of 40 rhizobacterial isolates were isolated from cotton rhizosphere and screened for improving cotton growth through the solubilization of phosphorus and zinc. Out of these 40 isolates, seven isolates (IA2, IA3, IA6, IA7, IA8, IA13, and IA14) efficiently solubilized insoluble rock phosphate while seven isolates (IA10, IA16, IA20, IA23, IA24, IA28, and IA30) were more efficient in solubilizing insoluble zinc oxide. In liquid media, strain IA7 (2.75 µg/mL) solubilized the highest amount of phosphate while the highest concentration of soluble zinc was observed in the broth inoculated with strain IA20 (3.94 µg/mL). Seven phosphate-solubilizing and seven zinc-solubilizing strains were evaluated using jar trial to improve the growth of cotton seedlings, and the results were quite promising. All the inoculated treatments showed improvement in growth parameters in comparison with control. Best results were shown by the combined application of IA6 and IA16, followed by the combination of strains IA7 and IA20. Based on the jar trial, the selected isolates were further characterized by plant growth-promoting characters such as siderophores production, HCN production, ammonia production, and exopolysaccharides production. These strains were identified through 16S rRNA sequencing as Bacillus subtilis IA6 (accession # MN005922), Paenibacillus polymyxa IA7 (accession # MN005923), Bacillus sp. IA16 (accession # MN005924), and Bacillus aryabhattai IA20 (accession # MN005925). It is hence concluded that the integrated use of phosphate-solubilizing and zinc-solubilizing strains as potential inoculants can be a promising approach for improving cotton growth under semi-arid conditions.

Paenibacillus polymyxa biofertilizer application in a tea plantation reduces soil N2O by changing denitrifier communities.

Increasing the use of nitrogen fertilizers in tea orchards has led to intense nitrous oxide (N2O) emissions. Foliar application of Paenibacillus polymyxa biofertilizer has been proven to be beneficial for organic tea production. In this study, tea yield and quality were significantly improved after application of P. polymyxa biofertilizer compared with the control but were not significantly different from chemical fertilizer treatments. However, the average N2O fluxes in tea fields treated with chemical fertilizers and biofertilizers (225 kg N·ha-1·year-1 for both) were 50.6-973.7 and 0.6-29.1 times higher than those in the control treatment, respectively. Pot experiments conducted to explore the mechanism of N2O reduction induced by P. polymyxa biofertilizer showed that applying P. polymyxa in addition to urea could reduce N2O fluxes by 36.5%-73.1%. Quantitative PCR analysis suggested that a significant increase in the quantity of nirK and nosZ genes was linked to the reduction of N2O, and high-throughput sequencing of nosZ revealed active and potentially efficient denitrifiers in different treatments. Our findings suggest that P. polymyxa biofertilizer is in line with the requirements of modern agriculture, which aims to increase product yield and quality while reducing negative environmental impacts.

Study on the simultaneous degradation of five pesticides by Paenibacillus polymyxa from Panax ginseng and the characteristics of their products.

The quality and safety of ginseng products were seriously affected due to the slow metabolism and long-term residual pesticides in ginseng. Microbial degradation is an effective method to degrade pesticide residues. In this study, ginseng endophytic Paenibacillus polymyxa was used to degrade pesticide residues. A method of simultaneous determination of fluazinam, BHC, PCNB, chlorpyrifos and DDT in ginseng roots and ginseng stems and leaves by GC was established. The sample was extracted with n-hexane and purified by Florisil solid phase extraction column. The limit of quantitation was 0.01 µg mL-1, the linear relationship was good (r ≥ 0.9901). 7 days after inoculated with P. polymyxa, the degradation rates of fluazinam, BHC, PCNB, chlorpyrifos, and DDT in the medium were 94.77%, 70.34%, 77.92%, 78.30%, 66.70%, respectively (P < 0.05). The safety of 5 pesticide degradation products was investigated by GC-MS. The results showed that after 7 days degradation, the main degradation products were alkanes, which are non-toxic and can't cause secondary pollution to the environment. The actual degradation results were verified by field experiments. The results indicated that after sprayed 5 times with P. polymyxa, the degradation rates of fluazinam, BHC, PCNB, chlorpyrifos and DDT in the ginseng roots were 66.07%, 46.24%, 21.05%, 72.40%, 54.21%, respectively (P < 0.05). The degradation rates in ginseng stems and leaves were 74.18%, 55.61%, 73.65%, 58.13%, 46.91%, respectively (P < 0.05). The results indicated that Paenibacillus polymyxa was an effective degradation strain of 5 pesticides.

Characterization and antifungal activity against Pestalotiopsis of a fusaricidin-type compound produced by Paenibacillus polymyxa Y-1.

Dendrobium nobile (D. nobile) is a valuable Chinese herbal medicine. The discovery of microbial resources from has provided a wealth of raw materials. Stalk rot, which is caused by Pestalotiopsis, is one of the most serious diseases of D nobile and has resulted in serious losses in production. However, an effective method for the prevention and control of stalk rot remains lacking. In this study, we aimed to identify a biocontrol strain against Pestalotiopsis. We isolated Paenibacillus polymyxa Y-1, an endophytic bacterium, from the stem of D. nobile. Three pairs of active metabolites isolated from this bacterium were identified as fusaricidin compounds. We then investigated the mechanism of fusaricidin compounds on Pestalotiopsis via proteomics. Proteomics data showed that the compounds mainly inhibit energy generation in the respiratory chain and amino acid biosynthesis of Pestalotiopsis.

Isolation, identification and characterization of Paenibacillus polymyxa CR1 with potentials for biopesticide, biofertilization, biomass degradation and biofuel production.

BACKGROUND: Paenibacillus polymyxa is a plant-growth promoting rhizobacterium that could be exploited as an environmentally friendlier alternative to chemical fertilizers and pesticides. Various strains have been isolated that can benefit agriculture through antimicrobial activity, nitrogen fixation, phosphate solubilization, plant hormone production, or lignocellulose degradation. However, no single strain has yet been identified in which all of these advantageous traits have been confirmed. RESULTS: P. polymyxa CR1 was isolated from degrading corn roots from southern Ontario, Canada. It was shown to possess in vitro antagonistic activities against the common plant pathogens Phytophthora sojae P6497 (oomycete), Rhizoctonia solani 1809 (basidiomycete fungus), Cylindrocarpon destructans 2062 (ascomycete fungus), Pseudomonas syringae DC3000 (bacterium), and Xanthomonas campestris 93-1 (bacterium), as well as Bacillus cereus (bacterium), an agent of food-borne illness. P. polymyxa CR1 enhanced growth of maize, potato, cucumber, Arabidopsis, and tomato plants; utilized atmospheric nitrogen and insoluble phosphorus; produced the phytohormone indole-3-acetic acid (IAA); and degraded and utilized the major components of lignocellulose (lignin, cellulose, and hemicellulose). CONCLUSIONS: P. polymyxa CR1 has multiple beneficial traits that are relevant to sustainable agriculture and the bio-economy. This strain could be developed for field application in order to control pathogens, promote plant growth, and degrade crop residues after harvest.