Algicidal activity of the bacterium, Pseudomonas fluorescens SK09, to mitigate Stephanodiscus hantzschii (Bacillariophyceae) blooms using field mesocosms

Abstract

The main goal of this study was to characterize mortality and trophic interactions of Stephanodiscus hantzschii (small centric diatoms) in the presence of an algicidal bacterium, Pseudomonas fluorescens HYK0210-SK09 (SK09) in outdoor mesocosm experiments with an extremely low temperature and also in direct application in a river. SK09 at an inoculation density of 5 £ 10 6 cells/mL (Experiment 1) and SK09 cells immobilized in activated carbon polyvinyl alcohol sponge carriers (Experiment 2) did not appear to attack S. hantzschii in a species-specific manner at temperatures close to freezing. Furthermore, SK09 did not control the diatom blooms when SK09 cells immobilized in the carriers were directly applied in the river. The dynamics of both the heterotrophic flagellate and ciliate abundances showed similar trends to the activity of algicidal bacteria; moreover the heterotrophic protists could not control the total bacterial density. Inorganic nutrient concentrations and conductivity remained unchanged compared with those in the control group. The results obtained in this study and previous results are important for assessing biological control using algicidal bacteria in the wild.

The microbiome of alpine snow algae shows a specific inter-kingdom connectivity and algae-bacteria interactions with supportive capacities

“…isolate and the microalga Ulva prolifera and found distinct bacterial genomic traits contributing to their symbiotic relationship [ 68 ]. In contrast, members of the bacterial family Pseudomonadaceae have also been reported to be able to produce algicidal compounds, indicating the specificity of growth-promoting and detrimental effects on different algae [ 69 , 70 ]. These findings are also reflected by the implemented co-occurrence network analyses.…”

Algicidal Bacteria: A Review of Current Knowledge and Applications to Control Harmful Algal Blooms

“…Only a few investigations have been conducted in open water in the field. To date, all reports on field applications of algicidal bacteria involved the use of bacterium Pseudomonas fluorescens HYK0210-SK09 (SK09) in river enclosures ( Jung et al, 2010 ; Kang et al, 2011 ; Noh et al, 2017 ). These reports underline the necessity of conducting field trials to confirm activity under conditions that may differ from those of laboratory culture experiments.…”

“…These reports underline the necessity of conducting field trials to confirm activity under conditions that may differ from those of laboratory culture experiments. Although SK09 exhibited strong species-specific algicidal activity against the winter-blooming harmful diatom Stephanodiscus hantzschi in laboratory culture experiments and indoor mesocosm studies ( Jung et al, 2008 , 2010 ), experiments conducted in less controlled field environments yielded inconsistent results ( Jung et al, 2010 ; Kang et al, 2011 ; Noh et al, 2017 ). Temperature likely played a role in the efficacy of SK09 along with other factors, including the high concentrations of algicidal bacteria required ( Seong and Jeong, 2013 ).…”

Nutritional status regulates algicidal activity of Aeromonas sp. L23 against cyanobacteria and green algae

“…While both the bacteria and the extracellular substances successfully controled single-species algal blooms in the laboratory conditions, this does not necessarily represent their applicability in the natural environment, which is more complex and variable [ 14 ]. In-situ mesocosm studies were performed to assess the risks and determine the ecological relevance of the laboratory-identified effects [ 13 , 15 ]. Abiotic factors such as light, pH, nutrient flux, and temperature influence the interaction between algae and bacteria [ 13 ].…”

“…Previous studies claimed that low-nitrogen conditions reduce the algal growth rate, subsequently increasing the intracellular lipid contents for energy storage [ 18 ]. It was also reported that the algicidal activity of algicidal strain Pseudomonas fluorescens SK09 is strongly associated with changes in nutritional status and consequent succession of phytoplankton species [ 15 ]. Despite the importance of nutritional status to the algicidal activity, information of algicidal activities on the different nutritional status is still lacking.…”