The potential use of bacterium strain R219 for controlling of the bloom-forming cyanobacteria in freshwater lake

Abstract

Cyanobacterial blooms become a serious environmental threat to the freshwater ecosystem, and several physical and chemical methods have been developed for controlling the blooms. In order to develop a biocontrol agent for controlling the blooms, we isolated a bacterial strain R219 that exhibited strong algicidal activity against the dominant bloom-forming species of Microcystis aeruginosa from Lake Tai in China. Based on 16S rDNA sequence analysis we determined the strain R219 to be Pseudomonas aeruginosa by the virtue of its sharing about 99.8% similarity with reference strains in the DNA databases. Biochemical and morphological tests were used to support the accurate identification as that of the bacterium P. aeruginosa. We also tested culture filtrate and ethyl acetate extract of strain R219 and showed both of them exhibited strong algicidal effect on the growth of M. aeruginosa at mid-exponential phase when the R219 filtrate and ethyl acetate extract were applied at various cell densities. Moreover, the P. aeruginosa filtrate showed high potency in removal of the mixed species bloom-forming cyanobacteria collected directly from the Lake Tai. When adding the filtrate of the strain R219 to the mixed-species cyanobacteria, the content of chlorophyll-a of the algae were reduced by as much as 80-90%. Oral acute toxicity assessment for strain R219 demonstrated that all the mice that received the broth or filtrate in doses of 0.5 or 2.0 g kg -1 were alive without any immediate behavioral changes within 14 days of administration of either broth or filtrate. These results indicate that the strain R219 may have potential for a use in controlling the bloom-forming cyanobacteria in freshwater ecosystems.

Investigation of the algicidal exudate produced by Shewanella sp. IRI-160 and its effect on dinoflagellates

“…Unless otherwise indicated, algicidal activity was calculated as a percentage based on in vivo Chl a fluorescence as described in Kim et al (2009) and Ren et al (2010) using the equation:…”

Performance evaluation of cyanobacteria removal from water reservoirs by biological method

“…(Peng et al, 2003;Zhao et al, 2005). P. aeroginosa has the ability to remove algae and microcystins (Choi et al, 2005;Roth et al, 2008;Ji et al, 2009;Ren et al, 2010). To possess lysis characteristics, a certain initial bacteria concentration is needed.…”

Pseudomonas aeruginosa UCBPP-PA14 a useful bacterium capable of lysing Microcystis aeruginosa cells and degrading microcystins

“…The reason for selection of Pseudomonas strains as preferred candidates was firstly due to the fact that bacterial strains of this genus account for more than half of all algicidal bacteria in freshwater reported since 2000 (Ren et al 2010) and that Pseudomonas is a metabolically versatile genus known as a biocontrol and bioremediation agent (Kang et al 2005). The second reason was availability of all species of this genus from bacteria culture collections.…”

“…Thus, control methods for removing both the cyanobacterium and the microcystins urgently need to be studied. In an effort to manage and mitigate the potentially devastating effects of M. aeruginosa, bacteria capable of mitigating bloom formation are considered to be one of the key biological agents in freshwater (Ren et al 2010). Lysis of Microcystis by bacteria was first reported in 1967 (Shilo 1970) and since then, many strains have been isolated (Sigee et al 1999).…”