• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.494-502
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• 2005

Antialgal bacteria and ciliates were tested alone and in combination for their abilities to decrease the densities of the warm-weather cyanobacterium, Microcystis aeruginosa, and the cold-weather centric diatom, Stephanodiscus hantzschii. Our results indicate that the density of M. aeruginosa was effectively suppressed by the bacterium, Streptomyces neyagawensis, and the heterotrich ciliate, Stentor roeselii. However, co-treatment with both bio-agents stimulated the algal density rather than decreasing it, suggesting that S. neyagawensis and S. roeselii may have an antagonistic relationship. Additional experiments revealed that the density of S. hantzschii was effectively suppressed by the bacterium, Pseudomonas putida, and by the above mentioned strain of S. roeselii. Co-treatment with both bio-agents had a higher antialgal activity than treatment with each alone, indicating that the bio-agents may act synergistically. These results suggest that the anti-alge efficacy of co-treatment with multiple biological control agents is likely to differ depending on the bio-agents and target organisms.

• Korean Journal of Microbiology
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• v.45 no.4
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• pp.362-367
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• 2009

Among total 176 strains with antialgal effects isolated from So-ok stream in Korea, Pseudomonas aeruginosa AJ1 showed the highest removal efficiency for an algal species Microcystis aeruginosa (clear zone of diameter 50.0 mm on algal lawn after 20 days). The algal growth was suppressed even when the supernatant of AJ1 culture was applied, suggesting that extracellular substances are responsible for its antialgal activity. The removal activity of AJ1 was optimal under the following condition: pH 8, $30^{\circ}C$, and mannitol as a carbon source. The antialgal activity of AJ1 appeared to be dependent of the growth phase of M. aeruginosa, i.e., the highest at the early phase, but not its own phase. As expected, the algicidal effect was improved as the amount of the treated supernatant was increased; the highest removal efficiency (80.3%) was achieved when 40 ml/L of the supernatant was used. Interestingly, however, the removal rate was opposite. The highest removal rate ($8.2{\mu}g$ chl-a/ml supernatant/day) was achieved when low concentration (10 ml/L) was applied. These results suggest that P. aeruginosa AJ1 is a promising biological agent to control the problematic algal bloom.

• Journal of Microbiology and Biotechnology
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• v.16 no.10
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• pp.1613-1621
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• 2006

Isolation and identification of algal lytic bacteria were carried out. Nine strains of algal lytic bacteria were isolated by the double-layer method using Anabaena flos-aquae as a sole nutrient. The isolate, AFK-13, showing the highest algal lytic activity was identified as Sinorhizobium kostiense based on the l6S rDNA sequence. The algal lytic experiments of the culture supernatants of AFK-13 demonstrated that the bacterial cell growth reached a maximum at 36-h culture, but the supernatant of 72-h culture exhibited the highest activity. Components among the extracellular products in the crude enzyme of the supernatant from S. kostiense AFK-13 culture were responsible for degradation of cell walls of Anabaena flos-aquae. Algal lytic assay tests of the culture supernatants suggest that the main substances for algal lytic activity could be proteinaceous. The activity of glucosidase was observed highly by polysaccharolytic analysis using the crude enzyme from S. kostiense AFK-13, whereas activities of galactosidase, mannosidase, rhamnosidase, and arabinosidase were also detected in low levels. The molecular weights (MW) of ${\alpha}-\;and\;{\beta}$-glucosidases were estimated to be approximately 50-100 kDa by the ultrafiltration method.