Effect Of Attached Bacteria Of Carbonic Anhydrase On The Growth Of Microcystis Aeruginosa

The carbon source of photosynthesis in algae mainly comes from the CO2in the air. The formation of water bloom will consume a lot of inorganic carbon in the water, which leads to the decrease of exogenous dissolved inorganic carbon (DIC) concentration and which leads to the increase of pH also. Because the diffusion rate of CO2into water is very low, the supply of CO2normally is limited for algae in water. So, the low-DIC and high-pH environment is not conducive to the growth of algae. In order to adapt to the environment of low DIC supply, cyanobacteria use effective CO2concentrating mechanism (CCM) to maintain the process of photosynthesis. Apparently extracellular DIC concentration plays an important role in this process. CO2in air by diffusion into the water after major into HCO3-, CA in waters can catalyze the CO2rapid formation of HCO3-balance. In natural waters, bloom-forming cyanobacterium Microcystis is wrapped in muncilge while plastic is home to a variety of bacteria, forming a microenvironment in which algae and bacteria are of close relationship. Bacteria and algae will release some enzymes, influencing each other’s living environment thereby affect each others’living environment. Microcystis cells surrounding the production of C A bacteria may have e a certain impact and influence the growth of Microcystis. So far, the impact of microcystis-attatching bacteria on carbon metabolism have not been studied in detail.To study the effect of attached bacteria on carbon metabolism of M. aeruginosa, the percentage of carbonic anhydrase (CA) producing bacteria in total attached bacteria was analyzed. The result showed that the ratio of CA producing bacteria is11.6%in a typical cyanobacterial bloom from Taihu Lake. An attached bacterium strain P201which produced large amount of extracellular carbonic anhydrase was isolated from M. aeruginosa assemblage. It was identified as a strain of Pseudomonas fluorescence by its16S rRNA molecular characteristic. The bacteria fermentation results show that:the P201produce extracellular CA in the beginning of its growth, and the CA activity is proportional to the bacterial concentration. The CA activity is proportional to the DIC concentration in different DIC conditions; bacterial growth rate is proportional to the temperature in different temperature conditions, the CA activity varies inversely with temperature; in different pH conditions, the bacteria P201grows best in pH8.0, the CA activity is directly proportional to the growth.Effects of P201on the growth of M. aeruginosa in different HCO3-concentrations were investigated. The results showed that in different HCO3-culture medium P201could partly promote the growth of M. aeruginosa, which is more obvious at low HCO3-culture, the CA activity is reduced by join the P201bacteria; in different pH conditions, the P201also shows certain stimulative effect, but the algae in pH10.0conditions grows worse; in different temperature culture, the CA producing attached bacteria play a little role in the growth of algae. The results showed that P201could partly promote the growth of M. aeruginosa by increasing the quantity of chlorophyll, which suggested that CA producing attached bacteria could enhance the growth of M. aeruginosa by regulating the ambient carbon environment.