Effects of colloids with different origin and size on the growth of photosynthetic bacteria
天然胶体是近岸海域细菌和浮游植物可利用氮的一个重要来源 ,其含量的增加可促进藻类的繁殖和生长 ,有时甚至引发赤潮。研究显示 ,细菌在高分子量胶体存在下的生长和代谢速率比在低分子量中的提高 3～ 6倍 ,暴露在阳光下的胶体有机物可释放生物可利用的富氮组分 ,进而提高细菌对胶体的分解。利用错流超滤技术从河流、河口、海洋水体和微藻培养液中提取胶体 ,研究了胶体来源和粒径对光合细菌 (PSB,沼泽红假单胞菌 Rhodopseudomonaspalustris)生长的影响。结果表明 ,在一定的胶体有机碳浓度范围 ,河流胶体 (0～ 2 81.0μmol/ L )、河口胶体 (0～ 12 1.2μmol/ L )、海洋胶体 (0～ 88.8μmol/ L )和生源胶体 (7.7～5 4 8.6μmol/ L )都能促进 PSB的生长 ,分别使其相对增长率平均提高了 4 7.3%～ 196 .2 % ,3.6 %～ 9.3% ,8.1%～ 10 .4 %和2 .4 %～ 6 .9%。其中 ,PSB在河流胶体中的相对增长率的平均值 (Y)与有机碳浓度 (CDOC)呈对数相关 (Y (% ) =- 193.7+70 .7ln CDOC) ,表明高浓度的河流胶体 ,对 PSB生长的促进效果更显著。两种生源胶体中 ,海水小球藻胶体 (0～ 5 4 8.6μmol/ L )对PSB生长的促进作用大于球等鞭金藻胶体 (7.7～ 384 .4 μmol/ L) ;PSB在粒径为 10 k D～ 0 .2 2 μm的海洋胶体中的生长大于Marine colloids are an important source of nitrogen for bacteria and phytoplankton growth. Elevated concentration of colloids may stimulate algal growth, however, sometimes result in red tides in coastal water. The research showed that bacterial growth and respiration in the presence of high-molecular-weight (HMW) dissolved organic matter (DOM) were 3～6 times greater than those in the low-molecular-weight (LMW) material, and that exposed to sunlight caused DOM to release nitrogen-rich compounds that were biologically available, and enhanced furthermore bacterial degradation of colloids.The effects of colloids with different source and size on the growth of photosynthetic bacteria (PSB, Rhodopseudomonas palustris) were studied. Colloids were isolated by cross-flow ultrafiltration from the cultured solution of Marine Chlorella and Isochrysis galbana, Xiamen Bay, Jiulongjiang Estuary and Jiulongjiang River (in China) respectively. The results showed that the average of relative increasing rates of PSB in the presence of riverine, estuarine, marine and biogenic colloids were respectively 47.3%～196.2%, 3.6%～9.3%, 8.1%～10.4% and 2.4%～6.9%, comparing to the control treatment when concentrations of colloidal organic carbon (C_(coc)) were 0～281.0μmol/L, 0～121.2μmol/L, 0～88.8μmol/L and 7.7～548.6μmol/L respectively. The results also showed that the average of relative increasing rates (Y) of PSB in the presence of riverine colloids were logarithmic correlation to concentrations of dissolved organic carbon(C_(DOC)), i.e. Y (%)=-193.7+70.7 lnC_(DOC), which indicated that riverine colloids of higher concentration have more effect on the growth of PSB than those of lower concentration. For biogenic colloids, the stimulation of colloids produced by Marine Chlorella (C_(coc)=0～548.6μmol/L) on the growth of PSB was greater than that by Isochrysis galbana (7.7～384.4μmol/L). Results also showed that the growth rates of PSB in marine colloids with 10kg～0.22μm size were 1.4 to 1.6 times greater than those in marine colloids with 1～10kD size. This was not only related to COC concentrations and salinity, but to higher abundance of glucose and galactose in the colloids. All the above results suggested that the colloids with different origin and size could be uptaken by PSB and spur PSB growth to different degree.