Proteomic Analysis Of Cyanobacterium Nostoc Flagelliforme In Response To PH Shift

The terrestrial cyanobacteria Nostoc lfageliforme is also called FaiCai, whichdistributed on arid or semiarid steppes of China where it is otfen exposed to extremeenvironment changes. Based on current research results and literature reports, thereason why Nostoc lfageliforme can adapt to adverse living environment is that theextracellular polysaccharides (EPS) of N. flagelliforme plays an important role inprotecting cells from various stresses. Additionally, according to present researchreports, Among various abiotic factors affecting their growth and secretion ofpolysaccharides in acquatic condition, the pH plays an important role in improvingits growth rate and the alkaline condition seems to be in favor of EPS accumulation.A similar phenomenon is also observed in this experiment. In the nature status, the N.flagelliforme thallus tends to live in high salinity and alkaline soil. However, Thecell culture sample of N. lfagelliforme hold a relative wide range of adaptability,compared with thallus. Long-term ifeld growth observation has showed that it onlypossesses6%growth rate per year. Considering its bacterial nature, liquidsuspension could be an alternative approach for a high yield production of thisspecies. Therefore certain constitutive overexpression of some genes must be presentin pH response, and to our best knowledge, there is little information that exists onthe relationships between accumulation of extracellular polysaccharides and thegenes encoding the proteins that regulate N. lfagelliforme growth and EPSbiosynthesis.(1) In this study, a comparative proteomic analysis using two-dimensional gelelectrophoresis (2D-E) coupled with MALDI-TOF-TOF/MS was performed in aquatic Nostoc lfageliforme to identiyf protein candidates involved inalkali stress response. Compairson of soluble proteins from the total fractionof cells grown on media set at pH7.5and9.0using2-DE identify sevenproteins, which showed signiifcant changes in abundance.(2) Among those proteins expression profiling at different external pH7.5and9.0, two unknown proteins (PP2C, Diaminopimelate) showed significantchanges corresponding to pH shift, and provided ideal target for furtherstudies in the mechanism of secretion polysaccharides (capsular and releasedpolysacchairdes). This study also identified three novel proteins, hithertounknown in Cyanobacterium.From this study, we have known that PP2C phosphoric acid proteinase isclosely associating with cell secretion of extracellular polysaccharide and nitrogenfixation process，2.5times compared with the control group decreased expression，atthe same time to participate in a cell’s outer membrane formed (Diaminopimelate)isomerase expression quantity increased by5.2times, the results may suggest thatcell cultures tend to be synthesized in alkaline environment thicker cell’s outermembrane and indirect evidence that cells and extracellular polysaccharideproduction process is in certain metabolic pathways are closely linked, in order tofurther study the N. lfagelliforme extracellular polysaccharide production process,this study provides reference and basis.