The Study On Cultivation Condition Of Thalassiosira Sp. And Its Sensitivity To Six Antibiotics

In the present paper, effects of nutritional and environmental factors on the growth of Thalassiosira sp. and the sensitivity of Thalassiosira sp. to six antibiotics were investigated primarily.The studies showed that Thalassiosira sp. could acclimate large range of temperature, it could maintain different growth at temperature from 9℃ to 27℃; and temperature from 15℃ to 21℃ was its apt temperature extent.Thalassiosira sp. has a wide range of light intensity adaptability, from illumination of 7.5 μmol m^-2 s^-1to 90 μmol m^-2s^-1 it could grow normally, furthermore the growth rate of Thalassiosira sp increased as illumination rose from 7.5μmol m^-2s^-1 to 90 μmol m^-2s^-1.Under salinity from 15‰ to 35‰, the growth rate of Thalassiosira sp. had little change with culture time extending; Thalassiosira sp. got the most growth rate at salinity 20‰.When NTH₄NO₃ was used as N resource, Thalassiosira sp. grew more rapidly and maintained longer at logarithmic period than used NHUCl and NaNOs as N resource of the same quantity; the apt range of N resource was from 1.2mmol/L to 1.8 mmol/L, and the high concentration (more than 4mmol/L ) of NH₄NO₃ inhibited the growth of Thalassiosira sp. to some degree.In case of different concentration of phosphorus, Thalassiosira sp. possessed well-nigh same growth rate; effected by various ratio of N to P, the growth of Thalassiosira sp. cultured in different medium differentiated from each other, and in the ratio of 16 to 1 (N:P) Thalassiosira sp grew most rapidly.Thalassiosira sp. cultured with different culture medium got different growth rate, maximal growth rate appears when Thalassiosira sp. was cultured with F medium. Meanwhile five dilute rate was the best dilute degree in fed-batch cultivationVitamin B₁ and B₁₂ could increase the growth rate when increased to some content, but more concentration had no negative influence on the growth of Thalassiosira sp.From pH7.5 to 9.0, Thalassiosira sp. got similar growth rate; Thalassiosira sp. grew more rapidly at early logarithmic period at pH8.0, while at late logarithmic period pH value might be 9.0; when pH value below 6.0 or above 10.0, the growth of Thalassiosira sp. was inhibited remarkably.At pH 8.0, pH8.5 and pH9.0, Thalassiosira sp. grew more rapidly when regulating pH with acetate acid than that of with hydrochloric acid; and while adding acetate acid (from 5mg/L to 60mg/L) in cultivation medium day by day, Thalassiosira sp. cultivated in these media could obtain greater growth rates than cultivated in normal medium.The sensitivity of Thalassiosira sp. to six antibiotics-Chloromycetin, Neomycin, Kanamycin, Ampicillin, Streptomcin, Erythromycin was studied, which would be the select agent for genetic transformation. The results indicated that Kanamycin (10-600mg/L), Neomycin (l-100mg/L) and Streptomcin (l-100mg/L) could not affect the growth of Thalassiosira sp. evidently; Ampicillin and Chloromycetin accelerated the growth of Thalassiosira sp. at low concentration (less than 0.lmg/L and l0mg/L respectively), but obviously restrained the growth of Thalassiosira sp. when their concentration increased; Erythromycin could inhibit the growth of Thalassiosira sp. remarkably at quite low concentration (0.05mg/L).