This project tried to prove the ability of carbohydrates to promote the population of PGPR from three angles to achieve the effect of promoting plant growth.
Maintenance of bacterial cultures
Ensifer fredii, Serratia proteamaculans and Pseudomonas fluorescens CHAO were used in this study. Bacterial cultures were prepared by transferring pure single colony of different bacteria, into LB broth and incubated at 28 °C for 12 hours. The bacterial cells were pelleted by centrifuging the culture at 5000 rpm for 5 min, followed by its re-suspension in sterilized distilled water. Uniform cell density of the bacterium was maintained by adjusting optical density (OD600=0.1).
Substrate preparation
Three concentration (0.01 %, 0.1 % and 1 %) of different substrates were evaluated for their effect on the growth of different bacteria. Different concentrations of substrates were prepared in sterile distilled water.
Growth of different bacteria in the presence of different carbohydrates in liquid media
One ml of 0.1 OD of different bacteria was added to the 4 ml of 0.01 %, 0.1% and 1% of different carbohydrates. The solutions were incubated at 28 °C. After 24 and 48 hours of incubation, 100 µl of solution of various dilutions were read by Cytation 5, Biotek. E. Each treatment consisted of five replicates. Sucrose was considered as control carbohydrate and was treated as experimental control.
Enumeration of bacteria in the soil amended with different carbohydrates
Garden soil was collected from University of Alberta, Edmonton, Alberta. Five grams of soil was sterilized twice in glass jars at 121 °C, 15psi for 20 min. Sterile soil was amended with 5 ml of bacterial culture (0.1 OD) and different concentration of different carbohydrate. Soil was incubated at room temperature for 7 days. 100 mg of soil was taken out on 3rd and 7th day of incubation. Various dilutions of soil solutions were prepared and 100 µl of the diluted bacteria were plated on the LB agar plates. The plates were incubated at 28 °C for 24 hours before colonies were counted. Soil amended with sucrose serve as experimental control. Each treatment consisted of 3 replicates.
Analysis
The multivariate statistics methods mainly focus on the "Growth of different substrate on the growth of tomato plants" part, this is still under working