| D3 (Rhodococcus rhodochrous.) strains that had a capability to utilize chlorpyrifos as the sole carbon and energy sources. D3 strains resistant to commonly antibiotics is studied in paper, the results that D3 strain on kanamycin, tetracycline resistance is less than 10μg .mL(-1), for chloramphenicol, streptomycin, ammonia Benzyl penicillin resistance is less than 5μg .mL(-1), the neomycin, erythromycin resistance is smaller, 2μg .mL(-1) and less than 0.5μg .mL(-1) respectively. D3 strain of chloramphenicol resistance to the domestication, to the chloramphenicol resistance to 30μg .mL(-1).The domestication had no serious effect on the chlorpyrifos -degradation ability of the strain .After the domesticated strain D3-X was inoculated into the soil, the colonizing dynamics of the D3-X in soil were studied by the method of enumeration of luminescent colonies on agar media. The results showed that D3-X successfully colonized both in the sterile soil and unsterile soil, and colonizing level of D3-X in sterile soil was higher than that of unsterile soil. The population of D3-X reached to the highest level, 4.9×10~7cfu/g and 2.3×10~7cfu/g soil respectively in the sterile soil and unsterile soil after 5 days.With time delaying the population decreased. The population of D3-X rised when peptone and barm paste were added into soil. The results of survival ability of D3-X in Yellow-Brown Soil,Yellow -red Soil and Shajiang Black Soil meant that strain D3-X could compete with other microbes for space and nutrition in different soils.Being prepared as microbial inoculant and inoculated on seeds of tomato, the colonizing dynamics and distribution of the strain D3-X in soil and rhizosphere of tomato plant in rhizoboxes were studied by the method of enumeration of luminescent colonies on agar media. The results showed that the strain colonized mainly in 0-10cm root segment in vertical direction. The population of D3-X reached to the highest level before 10 days after seeds planted. On the 5th day D3-X spread 6cm below seeds, the population in 0-2cm and 2-4cm root segment was 4.94×10~6cfu/g rhizosphere soil, 3.22×10~6cfu/g rhizosphere soil respectively. No luminescent bacteria were detected below 6cm, although wheat root length was beyond 6cm. On the 10th day, D3strain colonized mainly in 0-8cm root segment, although tomato root length was beyond 10cm, and on the 50th day, the population of D3-X in 0-2cm root segment reached to 1.11×10~3cfu/g root-soil and in 2-4cm8.45×10~2cfu/g root respectively in tomato rhizosphere and tomato rhizoplane. The results of rhizobox culture experiment showed that D3-X spread from seeds toward the direction of root tip, but not synchronized with the stretch of roots. D3-X was not detected in the region of tomato root tip.Colonizing level of D3-X in tomato rhizoplane was higher than that of tomato rhizosphere, and the population of D3-X decreased gradually along the root. The data indicated that the colonizing level of strain D3-X was relative to the distance between the root segment and the seeds, the shorter the distance was, the higher the coloning level was. In addition, the population of D3-X in the same root segment decreased gradually with time delaying.Resarching the effect of D3 strain of Chlorpyrifos on Bioremediation, the results indicated that D3 strain on the degradation of chlorpyrifos as the initial amount of the increase, the rate of soil degradation of chlorpyrifos accelerated, shortening the half-life, bacteria and repair of a positive correlation .In same amount of bacteria,the effect of plant on the decomposition half life of Chlorpyrifos is very remarkable. The degradation rate of chlorpyrifos in soil planted tomatoes is faster than that in soil not planted tomatoes. |
