Response of Cylindrospermopsis raciborskii and Pseudanabaena limnetica to a potential biological control agent, bacterium SG-3 (Lysobacter cf. brunescens)

• Published in: Lake and reservoir management 2007-09, Vol.23 (3), p.255-263
• Main Authors: Flaherty, Kathryn Wilkinson, Walker, H. Lynn, Britton, Clay H., Lembi, Carole A.
• Format: Article
• Language: English
• Subjects: Anabaena; aquatic bacteria; Bacteria; bioherbicide; biological control; Cyanobacteria; Cylindrospermopsis raciborskii; Freshwater; harmful algal blooms; Lyngbya; Oscillatoria; Pseudanabaena; taste and odor production; toxic cyanobacteria
• ISSN: 1040-2381; 2151-5530
• DOI: 10.1080/07438140709354014

A bacterium (SG-3) was reported by Walker and Higginbotham (2000) to lyse cells of filamentous planktonic species of cyanobacteria such as Anabaena, Oscillatoria and Lyngbya. We tested the efficacy of SG-3 in the laboratory to control Cylindrospermopsis raciborskii, a species with the potential to produce toxins, and Pseudanabaena limnetica, a species that causes taste and odor problems in water. Both were susceptible to SG-3 concentrations of 1.5 × 10 7 PFU/mL (PFU = plaque forming units), which was consistent with the concentrations used by Walker and Higginbotham (2000). In tests with a range of SG-3 concentrations (15 to 1.5 × 10 7 PFU/mL), cell numbers of the Lake Yale and Lake Griffin (FL) isolates of C. raciborskii in relation to untreated controls were reduced by 89-99% at SG-3 concentrations of 1.5 × 10 5 PFU/mL. The Lake Griffin isolate was somewhat more sensitive to SG-3 than the Lake Yale isolate. The calculated EC 50 and EC 100 for the Lake Griffin strain were 1.2 × 10 3 PFU/mL and 3.3 × 10 5 PFU/mL, respectively; the calculated EC 50 and EC 100 for the Lake Yale strain were 6.2 × 10 3 PFU/mL and 1.2 ×10 6 PFU/mL, respectively. The efficacy of SG-3 was also tested in lake water, which was spiked with the Lake Yale isolate of C. raciborskii; cell counts were reduced from 83 to 95% at SG-3 concentrations of 7.5 × 10 6 PFU/mL and higher. SG-3 concentrations greater than those that significantly reduced new cell growth were required to kill the initial populations of the Lake Yale strain present prior to treatment. Pretreatment cell numbers of the C. raciborskii isolates were consistent with those recorded in heavily infested lakes. Therefore, SG-3 at the higher end of the concentration range can kill bloom populations; however, it can also be applied at lower concentrations to act as an algistat on the initial cell populations while preventing additional bloom development, an approach that would avoid potential environmental damage from the cell release of toxins or taste and odor compounds.