Isolation and Identification of Bacteria in Phycospher from Microalga Chaetoceros muelleri and Growth Effect in a Bacterial-Algal Co-Culture System
HUANG Jin1, GUO Yongjun1,2, LIU Huiru1,2, LIANG Shuang1,2, LI Yongren1,2, ZHANG Tao3, WANG Donghao4, NIE Yuxuan4, LIANG Jian1,2
1. Tianjin Key Laboratory of Aqua-ecology and Aquaculture, College of Fisheries, Tianjin Agricultural University, Tianjin 300384, China; 2. Key Laboratory of Smart Breeding (Co-Construction by Ministry and Province), Ministry of Agriculture and Rural Affairs, Tianjin Agricultural University, Tianjin 300384, China; 3. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; 4. Tianjin Haisheng Aquaculture Co. Ltd, Tianjin 300272, China
Abstract：Epiphytic bacteria will promote growth and the accumulation of nutrients in the microalgal cells. In order to construct the symbiosis system of Chaetoceros muelleri and establish the rapid and stable propagation technology of C. muelleri, 1 mL of concentrated bacterial solution was added to the basic algae solution of the co-culture system of C. muelleri at algal cell density of 4.16×105 cells/mL during the aseptic growth phase, and the total bacterial concentrations of 106, 107 and 108 cfu/mL, respectively, and 1mL of NMB3 was added to the control group. The associated bacteria were isolated, identified using 16S rDNA and purified using the streak plate method. The changes in algal cell density, and chlorophyll-a content were monitored every 2 days during 10 days co-culture, and contents of dry weight, total polysaccharide, and total protein were determined on the 10th day. The results showed that two strains of epiphytic bacteria were isolated and identified from the C. muelleri culture medium, including strain M01 Algoriphagus marincola, and strain M02 Halomonas piezotolerans. Both strains led to increase in the biomass of C. muelleri in the co-culture system, and in elevated chlorophyll-a content of C. muelleri at concentrations of 106 cfu/mL and 107 cfu/mL for M01, with the maximal cell density (3.33×106 cells/mL) at a concentration of 108 cfu/mL throughout the entire culture period for M02 by the end of the culture, 19.28% higher than that in the control group (P<0.05). The chlorophyll-a content was found to be increased for M02 by 17.83%, reaching 3.51 μg/L (P>0.05). Both M01 and M02 resulted in improvement of accumulation of total protein in C. muelleri, with the maximal total protein content at 106 cfu/mL, 27.52% for M01 (P<0.05) and 11.39% for M02 (P>0.05) higher than that in the control group. However, both M01 and M02 did not significantly affect the dry weight or polysaccharide content of C. muelleri. In conclusion, the co-culture system with the two epiphytic bacterial strains improved both the growth efficiency and overall health of C. muelleri.
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2025, Vol. 44 
