| In recent years, algal bloom frequently outbreaks in the Shanzai reservoir in Fuzhou, posing a threat to the safety of drinking water. Microcystis aeruginosa is a dominant species in the algal bloom. During the occurrence of the algal bloom, we have discovered a type of short filamentous cyanobacteria which is often epiphytic or endogloeic in the colloid sheath of Microcystis. The cell number of this short filamentous cyanobacteria is only less than that of Microcystis. So far, the data about this kind of cyanobacteria are rare. Therefore, it is practically significant to study the identification of the species, the detection of toxic substances and the relationship between the two kinds of algae.Water samples were collected from the Shanzai reservoir during the occurrence of cyanobacteria bloom to isolate Microcystis and the epiphytic cyanobacteria. Two strains were isolated from water sample. The research was proceeded as follows:1. Morphological identification was carried out for observation using an optical microscope and an electron microscope, combined with laser scanning confocal microscope (LSCM). Furthermore,16S rRNA gene sequences from two species were extracted for analyzing and determining the species and taxonomic status. The results show that the two strains isolated from Shanzai reservoir are Psendanabaena mucicola PM201405 and Microcystis aeruginosa MC201406.2. Three methods including enzyme-linked immunosorbent assay (ELISA), high performance liquid chromatography (HPLC) and whole-cell PCR were used for detecting whether P.mucicola PM201405 can produce microcystin or not. The result of ELISA is positive. The result of HPLC is negative. The gene sequences of microcystin were not detected by whole-cell PCR. However, a sequence which cannot match any sequence of NCBI was amplified. So far, the function of this sequence is still unclear. Since all the three methods give different results and all of them may give false positive and false negative results, the toxicity of P.mucicola needs further investigation.3. Gas chromatography-mass spectrometry (GC-MS) is used for detecting whether P.mucicola PM 201405 produces odour substances or not. The result shows that P.mucicola PM201405 can not produce 2-MIB and geosmin. However, it can produce (3-cyclocritral and ?-ionone at later growth stage. Moreover, it can also produce a large amount of ?-ionone and then release the substance into the water.4. Five kinds of phosphate were selected to compare the absorption and utilization of phosphate between P.mucicola PM201405 and M. aeruginosa MC201406. The results show that the optimum phosphate for both of them is orthophosphate. However, the capacity of P.mucicola PM 201405 for absorbing and utilizing organophosphate is higher than that of M. aeruginosa MC 201406. Besides, the kinetics of nitrogen and phosphorus of absorption were preliminarily studied. The result shows that P.mucicola PM 201405 is more sensitive to the change of phosphorus concentration than to that of nitrogen.5. The optimal conditions of cultivation were studied. It is observed that BG11 is the optimal medium and 30? is the optimal temperature.6. Allelopathy between P. mucicola PM201405 and M. aeruginosa MC 201406 were studied with the methods of cell-free filtrate addition and co-cultured experiment. The results show that the cell-free filtrate of M. aeruginosa MC201406 can stimulate the growth of P. mucicola PM201405. However, the cell-free filtrate of P. mucicola PM201405 does not influence the growth of M. aeruginosa MC201406. On the other hand, the results from co-cultured test also reveal that M. aeruginosa MC201406 can accelerate the growth of P. mucicola PM201405. And the allelopathy is increased under the condition of N-limitation. |
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