太湖不同解有机磷菌株胞外碱性磷酸酶活性对蓝藻碎屑的响应

RESPONSES OF EXTRACELLULAR ALKALINE PHOSPHATASE ACTIVITY IN DIFFERENT ORGANIC PHOSPHORUS MINERALIZING BACTERIA STRAINS ISOLATED FROM LAKE TAIHU TO THE CYANOBACTERIUM DETRITUS

浮游细菌胞外碱性磷酸酶在湖泊磷循环过程中具有关键作用,但其与生物可利用性磷和颗粒态有机质之间的关系尚未得到充分的研究。研究以从太湖沉积物分离的3株解有机磷细菌(OPB)和东湖水中OPB菌群为实验对象,以蓝藻干物质为颗粒态有机质,系统分析了模拟条件下OPB的数量、不同大小颗粒所表现的胞外碱性磷酸酶活性(APA)与不同形态磷的浓度及其相互关系。从总体上讲,APA与OPB数量显著正相关,且明显反比于溶解反应性磷(SRP)浓度,在模拟实验过程中,不同菌株(群)所对应的SRP浓度均显著不同,故其解磷能力各异。从绝对活性及其在总活性中所占的比例来看,各处理间小颗粒(0.22—3.0μm)APA亦明显不同,而大颗粒(>3.0μm)APA和溶解态(<0.22μm)APA则无显著差异,因此,不同OPB种类解磷能力的差异主要由自由生活菌来体现。模拟实验初期(1—5 d)不同处理SRP浓度均剧减,细菌APA随之显著升高,其数量亦达峰值(6.2×108 CFU/mL),SRP浓度逐渐增加。实验后期(20—33 d)细菌数量大幅度减少,且伴随SRP和溶解态有机磷浓度的显著升高。因此,在缺磷且富含颗粒态有机质的条件下,OPB将产生胞外碱性磷酸酶,分解有机磷,进而满足其大量生长的需要,同时有效改变溶解态磷的形态与生物可利用性。

Excess phosphorus input into lakes always leads to eutrophication even to cyanobacterium bloom.Extracellular alkaline phosphatase of bacterioplankton plays an important role in phosphorus cycling,while its relations with particulate organic matter and bioavailable phosphorus remain unclear.In this study,the 3 strains of organic phosphorus mineralizing bacteria（OPB） isolated from the sediment of Lake Taihu together with the natural OPB assemblage in Lake Donghu were used to detect relations of extracellular alkaline phosphatase activity（APA）,including its sizes fractionations,with OPB abundances and phosphorus concentrations in different forms in the simulation experiment with cyanobacterium detritus as particulate organic matter.In general,APA showed a significantly positive relationship with the OPB numbers,and a significantly negative one with the soluble reactive phosphorus（SRP） concentration.Along the course of the experiment,the three strains and those in the nature assemblage responded to significantly different SRP concentrations showing their distinct abilities to mineralize organic phosphorus.Among the treatments containing different OPB strains the coarser（3.0 μm） and dissolved（0.22 μm） APA fractions were similar,while,the finer（0.22— 3.0 μm） fraction was significantly different in terms of the absolute activity and its ratio to the total one.At the initial stage of the experiment（1—5d） SRP concentration sharply reduced among the four different treatments,followed by a significant enhancement of total APA and a gradual increase in SRP concentrations,in the same time the OPB numbers peaked to 6.2×108 CFU/mL.In the last stage（20—33d） of the experiment,the OPB numbers drastically decreased,accompanied by a marked increase of SRP concentration and dissolved organic phosphorus concentration.Taken together,under the conditions of phosphorus deficiency and the enrichment of particle organic matter,OPB would produce extracellular alkaline phosphatase to decompose organic phosphorus to compensate phosphorus deficiency for their active growth,and change the form and bioavailability of soluble phosphorus effectively.