Increasing the autotrophic growth of Chlorella USTB ‐01 via the control of bacterial contamination by Bdellovibrio USTB ‐06

(i) To obtain and identify the predatory bacteria for the control of contaminated bacteria and to promote the autotrophic growth of Chlorella USTB‐01. (ii) To identify and measure the different cell numbers in microalgal culture using flow cytometer. A predatory bacterial strain was isolated using Escherichia coli BL21 as a sole prey host, which was identified as Bdellovibrio USTB‐06 by the analysis of 16S rDNA sequence. A flow cytometer was successfully used to identify and measure the cell numbers of Chlorella USTB‐01, the contaminated bacteria and Bdellovibrio USTB‐06 simultaneously in the autotrophic culture of Chlorella USTB‐01 according to the identification of the different cell sizes. With the addition of Bdellovibrio USTB‐06 at initial 104 plaque‐forming units per ml, the contaminated bacteria severely decreased by about five counts (in log10 CFU per ml) and the growth of Chlorella USTB‐01 was greatly increased by 37·0% compared with those of control respectively. Bdellovibrio USTB‐06 could effectively promote the growth of Chlorella USTB‐01 via the killing of the contaminated bacteria. Our study reveals a good biotechnology method to increase the growth of Chlorella USTB‐01 which is very important in the industry of microalgal culture.