title: Microbial nitrification in throughfall of a Japanese cedar associated with archaea from the tree canopy.
abstract: To investigate the nitrification potential of phyllospheric microbes, we incubated throughfall samples collected under the canopies of Japanese cedar (Cryptomeria japonica) and analyzed the transformation of inorganic nitrogen in the samples. Nitrate concentration increased in the unfiltered throughfall after 4 weeks of incubation, but remained nearly constant in the filtered samples (pore size: 0.2 and 0.4 µm). In the unfiltered samples, δ(18)O and δ(15)N values of nitrate decreased during incubation. In addition, archaeal ammonia monooxygenase subunit A (amoA) genes, which participate in the oxidation of ammonia, were found in the throughfall samples, although betaproteobacterial amoA genes were not detected. The amoA genes recovered from the leaf surface of C. japonica were also from archaea. Conversely, nitrate production, decreased isotope ratios of nitrate, and the presence of amoA genes was not observed in rainfall samples collected from an open area. Thus, the microbial nitrification that occurred in the incubated throughfall is likely due to ammonia-oxidizing archaea that were washed off the tree canopy by precipitation.
authors.affiliation: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 Japan ; Center for Environmental Science in Saitama, Kazo, Saitama 347-0115 Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 Japan.
authors.forename: Ayato
authors.initials: A
authors.lastname: Kohzu
authors.affiliation: Graduate School of Frontier Science, The University of Tokyo, Kashiwa, Chiba 277-8562 Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Suda
authors.affiliation: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Yamamura
authors.affiliation: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 Japan.
authors.forename: Takejiro
authors.initials: T
authors.lastname: Takamatsu
authors.affiliation: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Takenaka
authors.affiliation: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 Japan.
authors.forename: Masami Kanao
authors.initials: MK
authors.lastname: Koshikawa
authors.affiliation: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Hayashi
authors.affiliation: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 Japan.
authors.forename: Mirai
authors.initials: M
authors.lastname: Watanabe
keywords: Ammonia-oxidizing archaea; Nitrification; Phyllosphere; Throughfall; amoA