Cultural Condition, Colonizing Dynamics And 16SrDNA Sequence Analysis Of PGPR Strains Isolated From Gramineous Forage

Cultural condition,colonizing dynamics and 16SrDNA sequence analysis of PGPR (plant growth promoting rhizobacteria) strains isolated from gramineous forage were carried out, the results were obtained as follows: 1. The cultural condition of PGPR　strains Temperature,pH,light,cultural method,acid or alkali producing,and salt (NaCl) tolerance of 9 PGPR strains isolated from Gramineous Forage were tested,the results showed that all the PGPR strains could grow in the temperature range from 5℃～45℃,and optimum temperature for 178,O-6,Dry6　strains was　35℃,for　X5,173,Y5,C-6 strains　was 30℃,for N4 strain　was 25℃～35℃,for 86 strain was 25℃;most of PGPR strains prefered to neutral or alkaline condition,strains　178,O-6,N4 and X5　were preferable to alkali condition especially;light was beneficial to PGPR's growth;all of them produce alkali;most of PGPR strains were not sensitive to NaCl concentration;all the strains were aerobiotic bacteria. 2. Resistance marking and colonization dynamics of PGPR strains Mutant strains of　PGPR resistance to Rifampicin were acquired by continuously screening on series of different concentration of Rifampicin media.Compared with original strains,the ability of phosphorus solubilizing,nitrogen fixation and IAA producing weren't change or a little increase,and colonial morphology were slightly changed.　　The marked PGPR strains could be colonized in the rhizosphere and rhizoplane of oat effectively,but couldn't be colonized in the histoplan,and colonization could be classified three types:1) The population　of　strains　C-6 and 86 reduced gradually during test time,the population decreased to 2.26×106cfu/g and 1.54×105 cfu/g at the 36th days respectively.2)The population　of　strains O-6,Dry6,173,Y5,X5　increased at the beginning then decreased in the rhizosphere,e.g.,their population　reached to the highest at the 6th day except 173　(12th), then reduced gradually;but in the rhizoplane,the trend was first decreased,then increased,finally decreased again (the reducing trend was slowly).3) The population of　strains N4 and 178 strains'population reduced about 10 times at the 6th day,then raised gradually and reached to the hightest point at the12th day,and decreased again. 3. 16SrDNA sequence analysis of O-6, C-6 and 86 strains　16SrDNA sequence of strains O-6, C-6　and　86 were analysed,the results show that their homogeneous at the rate of 99% to the members of Alcaligenes, Bacillus subtilis, Escherichia coli (Accession number were AY556408, AY805232 and Z83205 in GenBank) resepctively.Therefore,the position of three strains in bacterial phylogeny were located　and　were identified as Alcaligenes,Bacillus subtilis and Escherichia coli .