Exploration Of Molecular Mechanism Of Phosphate-Solubilizing On Paenibacillus Mucilaginosus And Its Effects On Soil Ecological Effect

Paenibacillus mucilaginosus, an important Plant Growth-Promoting Rhizobacteria(PGPR), was widely used in microbial fertilizer as production strains. It could effectivelyincrease the content of soluble phosphorus and potassium in soil, promote plant growth.However, its molecular mechanism on phosphate solubilization and dissolving potassiumwere controversial up to now. Besides, it was not clear about the influence on soil ecologicaleffect, when P. mucilaginosus was used into soil. Thus, its development and adaptation wererestricted to some extent. P. mucilaginosus3016, as one of the classic strains, was isolatedfrom rhizosphere soil and widely used in microbial fertilizer for most manufacturers. It couldutilize amylase, produce little acid, form plump capsule and release mobile nutritional ions,soluble content of K, P and other beneficial elements in the soil, and had been finished thewhole genome sequencing at2012.In this paper, a field experiment was carried out with tester strain of P. mucilaginosus3016. Four different treatments were designed, such as T1(blank control), T2(no fertilizersbut P. mucilaginosus3016), T3(P. mucilaginosus3016cooperated with half of the regularfertilizer dose), T4(the regular fertilizer dose). The influence on growth characteristics ofpeanuts and lettuce, soil microbial quantity and enzyme activity were analyzed for everytreatment. So were compositional and functional diversity of soil microflora by DGGE. Thecorrelations between soil enzyme activity, soil microbial quantity and crop yield werediscussed. Proteomics technique was followed. The proteins of P. mucilaginosus onphosphorus and phosphorus deficiency were extracted, respectively, and were separated bytwo-dimensional gel electrophoresis. Then, the differential proteins were identified byMOLDI-TOF mass spectra for exploring molecular mechanism of phosphate solubilizing on P.mucilaginosus3016. The conclusions were as follows:(1) P. mucilaginosus3016could increase the pods number per peanut plant, pods weigh per peanut plant, hundred pods weight, seed-producing rate of peanut and stem diameter, netweight per lettuce plant. Under the treatment of P. mucilaginosus3016cooperated with halfof the regular fertilizer dose, those growth characteristics were higher than that under thecontrol with a rote of27.1％、22.9％、7.8％、2.4％、10.3％、7.5％and31.7％. The nutrientcontent of peanut kernel and stem leaf was as same as regular fertilizer dose or some higherthan it, and the potassium content was very significant compared with controls(P<0.01),which reached to0.55%and1.19%, respectively.(2) The yield of peanut and lettuce under T3treatment were the highest (5281.38kg/hm2and11674.5kg/hm2) with a increase rate of10.3%and19.6%, respectively. Thus, P.mucilaginosus3016cooperated with half of the regular fertilizer dose could effectivelyincrease the plant yield, which may be an optimal fertilizing measure.(3) The soil enzyme activities under T2treatment or T3treatment for inoculation of P.mucilaginosus3016in peanut harvesting time was significantly higher than T1or T4(P<0.05). In conclusion, the number of bacteria and actinomycetes quantities under T3treatment was increased during growing period, and the fungi was inhibited, which may beplay important roles in the improvement of soil quantity, structure, microbial diversity,function and fertility.(4) PCR-DGGE was used to analyse the soil microflora composition of differenttreatments. Some preponderant bands of the DGGE profiles were sequenced. The resultsshowed that, P. mucilaginosus3016could increase soil microbial diversity effectively, andpromote the quantity of Sphingomonas and Bacillus growth especially. But the regularfertilizer treatment reduced the soil microbial diversity effectively.(5) Proteomic technique was used to analyse the proteome of P. mucilaginosus3016cultured in phosphorus and phosphorus-free medium. The results showed that, there were29up-regulated proteins and36down-regulated proteins in expression with significantdifference for P. mucilaginosus3016cultured in phosphorus medium. Differentially displayedproteins were analyzed by MALDI-TOF-MS, and35of them were identified. Most of themwere relevant to metabolism, transport, translation, molecular chaperone and stress protein.In conclusion, P. mucilaginosus3016could significantly increase the quantity of bacteria,actinomycetes, soil urease activity and microbial diversity, which may be play important roles in the improvement of soil structure and fertility. P. mucilaginosus3016cooperated with halfof the regular fertilizer dose could not only increase peanut yield and improve plant characters,but also improve soil ecological effect, which may be a optimal fertilizing measure. On theother hand, the results of the different expression proteins suggested that, the process ofphosphate solubilization in P. mucilaginosus3016were related to carbohydrate and serineprotease. In this process, phosphate group may be entre the body and participate in glucolysis,pentose phosphate pathway, tricarboxylic acid cycle, electron transfer and oxidativephosphorylation, which may be a new insight to reveal molecular mechanism of phosphatesolubilization on P. mucilaginosus3016.