title: Interspecies interactions are an integral determinant of microbial community dynamics.
abstract: This study investigated the factors that determine the dynamics of bacterial communities in a complex system using multidisciplinary methods. Since natural and engineered microbial ecosystems are too complex to study, six types of synthetic microbial ecosystems (SMEs) were constructed under chemostat conditions with phenol as the sole carbon and energy source. Two to four phenol-degrading, phylogenetically and physiologically different bacterial strains were used in each SME. Phylogeny was based on the nucleotide sequence of 16S rRNA genes, while physiologic traits were based on kinetic and growth parameters on phenol. Two indices, J parameter and "interspecies interaction," were compared to predict which strain would become dominant in an SME. The J parameter was calculated from kinetic and growth parameters. On the other hand, "interspecies interaction," a new index proposed in this study, was evaluated by measuring the specific growth activity, which was determined on the basis of relative growth of a strain with or without the supernatant prepared from other bacterial cultures. Population densities of strains used in SMEs were enumerated by real-time quantitative PCR (qPCR) targeting the gene encoding the large subunit of phenol hydroxylase and were compared to predictions made from J parameter and interspecies interaction calculations. In 4 of 6 SEMs tested the final dominant strain shown by real-time qPCR analyses coincided with the strain predicted by both the J parameter and the interspecies interaction. However, in SMEII-2 and SMEII-3 the final dominant Variovorax strains coincided with prediction of the interspecies interaction but not the J parameter. These results demonstrate that the effects of interspecies interactions within microbial communities contribute to determining the dynamics of the microbial ecosystem.
authors.affiliation: Laboratory of Food Crops, Institute of Tropical Agriculture, Universiti Putra Malaysia Serdang, Malaysia ; Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan.
authors.forename: Fatma A A
authors.initials: FA
authors.lastname: Aziz
authors.affiliation: Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan.
authors.forename: Kenshi
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Department of Environmental and Life Sciences, Toyohashi University of Technology Toyohashi, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ohtaki
authors.affiliation: Department of Environmental and Life Sciences, Toyohashi University of Technology Toyohashi, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Sagegami
authors.affiliation: Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan.
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Hirai
authors.affiliation: Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Seno
authors.affiliation: Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Mizuno
authors.affiliation: Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan.
authors.forename: Yuma
authors.initials: Y
authors.lastname: Inuzuka
authors.affiliation: Department of Mathematics, Shimane University Matsue, Japan.
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Saito
authors.affiliation: Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Tashiro
authors.affiliation: Department of Environmental and Life Sciences, Toyohashi University of Technology Toyohashi, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Hiraishi
authors.affiliation: Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Futamata
keywords: chemostat; interaction; microbial ecosystem; phenol; population dynamics; self-organization