title: Changes in the community structure of free-living heterotrophic bacteria in the open tropical Pacific Ocean in response to microalgal lysate-derived dissolved organic matter.
abstract: Dissolved organic matter derived from phytoplankton (DOMP) can affect the bacterial biomass and community structure in aquatic ecosystems. Here, we examined the community response of free-living heterotrophic bacteria, with respect to cellular nucleic acid levels, to the DOMP lysates derived from three phytoplankton strains in the open tropical Pacific. The free amino acid (FAA) composition of each DOMP lysate differed among the microalgal strains. Terminal restriction fragment-length polymorphism analyses with 16S rRNA genes revealed that the community shifts of high nucleic acid (HNA) and low nucleic acid (LNA) bacteria varied significantly with the different DOMP lysate treatments. Furthermore, the FAA composition in DOMP lysates significantly affected the bacterial community shifts in HNA and LNA. Similarity percentage analysis using 16S rRNA gene deep-sequencing revealed that the DOMP lysates from the pelagophyte Pelagomonas calceolata caused relatively large community shifts with Alcaligenes predominating in the HNA fraction. In contrast, the DOMP lysate from the diatom Thalassiosira oceanica induced a community shift in the LNA fraction with a predominance of uncultured Actinobacteria Thus, the data indicate that the DOMP lysates from different microalgae constitute a primary factor altering the dominant bacterial groups in the open ocean.
authors.affiliation: Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan yuyatada@ees.hokudai.ac.jp.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Tada
authors.affiliation: Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Suzuki
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D017753:Ecosystem; D052836:Heterotrophic Processes; D058086:Microalgae / Q000737:chemistry / Q000378:metabolism*; D009930:Organic Chemicals / Q000378:metabolism*; D010140:Pacific Ocean; D010802:Phylogeny; D010839:Phytoplankton / Q000737:chemistry / Q000378:metabolism*; D012150:Polymorphism, Restriction Fragment Length; D012623:Seawater / Q000382:microbiology*
chemical_list: D009930:Organic Chemicals
keywords: Pacific Ocean; amino acids; dissolved organic matter; high- and low-nucleic acid bacteria; marine bacteria; marine phytoplankton