Numbers and metabolic activities of heterotrophic bacteria,ammonifiers and ammonia oxidizing bacteria in the Nereis close- recirculating culture system
Ma YueXin;Shao Hua;Zhou YiBing;Liu ChangFa;Li Jiang;Tan HongLiang
Abstract: Two rounds experiments were designed with four close-recirculating culture systems （A, B and C, D） of Neries （Perineries aibuhitensis Grube） according to the density （worms/m^2） and feeding rate： 1049 and 20% （A）, 1049 and 10% （B）, 833 and 5% （C）, and 641 and 5% （D）, respectively. In the first round experiment, 15 strains of bacteria were isolated from the biofilms associated with sands in system A, and system B after maturation of biofilm. The oxygen uptake rates of heterotrophic bacteria isolates （eight strains） were （10.88±0.73）-（114.98±50.62）g/（mg protein·d）, of which H3 was the highest. The ammonification rates of ammonifier isolates （seven strains） were （0.76±0.57）-（1.47±1.09）g/（mg protein·d）, and the activities of each isolate were similar. Meantime the biofilms associated with sands were observed by scanning electron microscope. The various shapes of bacteria were found. In the second round experiment, the numbers of heterotrophic bacteria, ammonifiers and ammonia oxidizing bacteria in system C, and system D were counted using PC, MPN methods, and their metabolic activities were determined during the forming and maturing periods of biofilm associated with sand in biological filter, The results show that the numbers of three physiological groups of bacteria increased gradually with the forming of biolfilm： the number of heterotrophic bacteria was 10^5-10^7 CFU/mL （wet sand）, the numbers of ammonifiers in system C and system D were 10^6-10^8 CFU/mL （wet sand） and 10^4-10^6 CFU/mL （wet sand）, respectively, and both kept stable after maturation of biofilm. The number of ammonia oxidizing bacteria first increased to the maximum, then decreased slightly with the long period after being fed. The changing trends of oxygen uptake rates of heterotrophic bacteria and ammonification rates of ammonifiers were similar to those of numbers of bacteria. The influences of substrate concentrations, temperature and pH on ammonification rates o
2005, Vol. 20 
