title: Mn accumulation in a submerged plant Egeria densa (Hydrocharitaceae) is mediated by epiphytic bacteria.
abstract: Many aquatic plants act as biosorbents, removing and recovering metals from the environment. To assess the biosorbent activity of Egeria densa, a submerged freshwater macrophyte, plants were collected monthly from a circular drainage area in Lake Biwa basin and the Mn concentrations of the plants were analysed. Mn concentrations in these plants were generally above those of terrestrial hyperaccumulators, and were markedly higher in spring and summer than in autumn. Mn concentrations were much lower in plants incubated in hydroponic medium at various pH levels with and without Mn supplementation than in field-collected plants. The precipitation of Mn oxides on the leaves was determined by variable pressure scanning electron microscopy-energy dispersive X-ray analysis and Leucoberbelin blue staining. Several strains of epiphytic bacteria were isolated from the field-collected E. densa plants, with many of these strains, including those of the genera Acidovorax, Comamonas, Pseudomonas and Rhizobium, found to have Mn-oxidizing activity. High Mn concentrations in E. densa were mediated by the production of biogenic Mn oxide in biofilms on leaf surfaces. These findings provide new insights into plant epidermal bacterial flora that affect metal accumulation in plants and suggest that these aquatic plants may have use in Mn phytomining.
authors.affiliation: Graduate School of Environmental Science, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.
authors.forename: Kousuke
authors.initials: K
authors.lastname: Tsuji
authors.affiliation: Graduate School of Environmental Science, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.
authors.forename: Takuma
authors.initials: T
authors.lastname: Asayama
authors.affiliation: School of Environmental Science, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.
authors.forename: Nozomi
authors.initials: N
authors.lastname: Shiraki
authors.affiliation: School of Environmental Science, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Inoue
authors.affiliation: School of Environmental Science, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.
authors.forename: Erina
authors.initials: E
authors.lastname: Okuda
authors.affiliation: School of Environmental Science, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.
authors.forename: Chizuru
authors.initials: C
authors.lastname: Hayashi
authors.affiliation: School of Environmental Science, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.
authors.forename: Kazuma
authors.initials: K
authors.lastname: Nishida
authors.affiliation: School of Environmental Science, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hasegawa
authors.affiliation: School of Environmental Science, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.
authors.forename: Emiko
authors.identifier: http://orcid.org/0000-0002-8479-8034
authors.initials: E
authors.lastname: Harada
mesh_terms: D018441:Biofilms; D020585:Comamonas / Q000235:genetics / Q000502:physiology; D019015:Geologic Sediments / Q000032:analysis; D031321:Hydrocharitaceae / Q000378:metabolism* / Q000382:microbiology*; D018527:Hydroponics; D007564:Japan; D008345:Manganese / Q000378:metabolism* / Q000493:pharmacokinetics; D059013:Microbial Consortia; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology*; D011549:Pseudomonas / Q000235:genetics / Q000502:physiology; D012336:RNA, Ribosomal, 16S; D012231:Rhizobium / Q000235:genetics / Q000502:physiology
chemical_list: D012336:RNA, Ribosomal, 16S; D008345:Manganese
keywords: Lake Biwa; Leucoberbelin blue; Mn-oxidizing bacteria; VPSEM-EDX; aquatic plant; biofilm; epiphytic bacterium; manganese