title: A mutualistic interaction between the bacterium Pseudomonas asplenii and the harmful algal species Chattonella marina (Raphidophyceae).
abstract: Several studies on various Chattonella species have reported that bacteria may play an important role in Chattonella bloom initiation, however, no studies have described how these bacteria promote the growth of C. marina. The interaction between C. marina and bacteria was investigated for identification and characterization of potential growth-promoting bacteria. In preliminary tests, the growth promoting effect of Pseudomonas species (25 strains) was investigated and P. asplenii (≥2.27) was determined as a growth-promoting bacteria for both C. marina strains (CCMP 2049 and 2050). This bacterium exerted optimal growth-promoting effects on C. marina, causing an increase in the initial density of P. asplenii to approximately 1×107cellsmL-1, which was used as the initial density in this study. To determine whether the growth-promoting activity was direct or indirect, P. asplenii was incubated in the algal media and then a filtrate of this culture was added to both C. marina strains. The P. asplenii filtrate stimulated the growth of C. marina and maintained the growth-promoting effects after high temperature (121°C for 20min) and pressure (15psi) treatment. Thus, P. asplenii is able to promote C. marina growth through the release of a heat-resistant substance, such as inorganic nutrients. A nutrient analysis indicated that this bacterium elevated the phosphate concentration. Interestingly, P. asplenii was unable to survive in phosphate-limited media but could grow in phosphate-limited media incubating C. marina. Moreover, this bacterium could secrete significantly more phosphate in the presence of C. marina (p<0.0001). These results suggested that P. asplenii and C. marina may have a mutualistic interaction.
authors.affiliation: Department of Life Science, College of Natural Sciences, Hanyang University, Seoul 04763, South Korea; Research Institute for Natural Sciences, Hanyang University, Seoul 04763, South Korea.
authors.forename: Bum Soo
authors.initials: BS
authors.lastname: Park
authors.affiliation: Department of Life Science, College of Natural Sciences, Hanyang University, Seoul 04763, South Korea.
authors.forename: Jae-Hyoung
authors.initials: JH
authors.lastname: Joo
authors.affiliation: Department of Life Science, College of Natural Sciences, Hanyang University, Seoul 04763, South Korea.
authors.forename: Kyung-Duck
authors.initials: KD
authors.lastname: Baek
authors.affiliation: Department of Life Science, College of Natural Sciences, Hanyang University, Seoul 04763, South Korea; Research Institute for Natural Sciences, Hanyang University, Seoul 04763, South Korea. Electronic address: hanms@hanyang.ac.kr.
authors.forename: Myung-Soo
authors.initials: MS
authors.lastname: Han
mesh_terms: D011549:Pseudomonas / Q000502:physiology*; D058009:Stramenopiles / Q000502:physiology*; D013559:Symbiosis
keywords: Chattonella marina; Growth-promoting characteristics; Mutualistic interaction; Pseudomonas asplenii