Study On The Screening And Mechanism Of Low-temperature Phosphorus-releasing Bacteria In The Soil Of Penguin Island,Antarctica

Phosphorus is an important element in plants,and it involved in many metabolic activities.The lack of phosphorus has a significant impact on the growth of crops.At present,most of the cultivated land in China are faced with the problem of insufficient available phosphorus,the main reason is the accumulation of unavailable phosphorus comes from the fixation of phosphorus by a variety of metal ions in the soil.These unavailable phosphorus can only be used in crops by a series of transformations to form soluble ion-based phosphate or organic phosphate with low molecular weight.The most effective way is microbial transformation.In order to meet the demand of crop growth in the current season,phosphorus fertilizer is often used in agriculture to improve the yield,but the further adsorption and fixation of complex substances in soil also promotes a lower utilization rate of phosphorus fertilizer.The long-term excessive application of phosphorus fertilizer not only causes serious soil consolidation,but also leads to a series of environmental pollution problems.The Ministry of Agriculture issued a call for negative increase in the use of fertilizer and pesticide for the serious problems and microbial fertilizers have also be well-known to the public.The principle is to apply microorganisms with the ability of transforming unavailable phosphorus into the farmland soil as fertilizer,so that crops can use the phosphorus accumulated in the soil.The microorganisms that are currently developed into fertilizer mainly play a role in the normal temperature,but in low temperature,the low activity and the ability to solve phosphorus are reduced,which can not be used normally.The soil temperature in China is lower than 15? for about 5 months,while the minimum soil temperature in most areas in winter even reaches below 0?.Therefore,it is necessary to find the phosphorus removal microorganisms can be applied to lowtemperature soil and further to develop microbial fertilizer suitable for low-temperature environment,which is of great significance for the development of green agriculture and the solution of the bottleneck of microbial fertilizer.In this paper,the low-temperature phosphate solubilizing bacteria were screened and purified from the soil samples collected from Kee Island,Antarctica.The ability of phosphate solubilizing was verified by phosphate solubilizing circle method and molybdenum antimony anti colorimetric method,and the screened phosphate solubilizing bacteria were identified and their genetic relationship was analyzed.The growth characteristics of phosphate solubilizing bacteria were preliminary analyzed,and then,the ability of phosphate solubilizing of phosphate solubilizing bacteria under different culture conditions was further analyzed and optimized.Transcriptome sequencing technology was used to analyze the different genes of phosphate solubilizing bacteria at different temperatures,and to explore the mechanism of phosphate solubilizing ability of bacteria at low temperature.The main results are as follows?1.A total of 12 strains of bacteria were screened out from 5 soil samples,all of which belonged to Pseudomonas.The results of preliminary determination of phosphate solubilizing ability showed that the phosphate solubilizing ability of six strains of bacteria was similar to that of the phosphate solubilizing bacteria used at normal temperature,and the phosphate solubilizing ability of Pseudomonas Siemens strain ilq215(Pd12)was the strongest.2.The growth characteristics of three low temperature phosphate bacteria selected were studied.It was found that low temperature did not affect the growth of the phosphorolysis,but the growth rate was slightly slowed down.The growth rate of Pd8 strain was slightly different from the other two strains at 30?,and the bacteria almost stopped growing.The results showed that the ability of phosphorus removal was the strongest when p H=6,and the ability of phosphorus removal increased with the increase of salinity in the range of less than 30 g/l.The phosphorus removal capacity of the three bacterias was the highest at 10?,and the capacity of P-removal was Pd8 < Pd9 < Pd12.3.The mechanism of phosphorus removal was further explored by transcriptional sequencing of Pseudomonas frederiksbergensis strain qt-128(Pd9).The results showed that there were 34 specific genes at 10?.The gene BLW70?RS18110 can synthesize glucose dehydrogenase(GDH),and work with the coenzyme pyrroloquinoline quinone(PQQ)to promote the direct oxidation of glucose to gluconic acid.It can also convert inorganic phosphate into phosphate ion while reducing p H of bacteria solution.The analysis of the enrichment of GO indicated that the difference genes were mainly concentrated in the Glu and Mg binding functions of molecular functional groups.The up regulation of glutamine synthetase and phenylalanine transporter RNA ligase further indicates that glutamine plays an important role in the process of phosphorus removal at low temperature.The results of enrichment analysis of KEGG pathway showed that the significant pathways of the gene differences were peptidoglycan biosynthesis pathway and fructose and mannose metabolism pathway.The main trend was glutamate alanine ligase,phospho-n-acetylaminotransferase all down-regulated,glycodehydrogenase and lysase all up-regulated.