title: In situ stable isotope probing of phosphate-solubilizing bacteria in the hyphosphere.
abstract: This study used a [(13)C]DNA stable isotope probing (SIP) technique to elucidate a direct pathway for the translocation of (13)C-labeled photoassimilate from maize plants to extraradical mycelium-associated phosphate-solubilizing bacteria (PSB) that mediate the mineralization and turnover of soil organic phosphorus (P) in the hyphosphere. Inoculation with PSB alone did not provide any benefit to maize plants but utilized the added phytate-P to their own advantage, while inoculation with Rhizophagus irregularis alone significantly promoted shoot biomass and P content compared with the control. However, compared with both sole inoculation treatments, combined inoculation with PSB and R. irregularis in the hyphosphere enhanced organic P mineralization and increased microbial biomass P in the soil. There was no extra benefit to plant P uptake but the hyphal growth of R. irregularis was reduced, suggesting that PSB benefited from the arbuscular mycorrhizal (AM) fungal mycelium and competed for soil P with the fungus. The combination of T-RFLP (terminal restriction fragment length polymorphism) analysis with a clone library revealed that one of the bacteria that actively assimilated carbon derived from pulse-labeled maize plants was Pseudomonas alcaligenes (Pseudomonadaceae) that was initially inoculated into the hyphosphere soil. These results provide the first in situ demonstration of the pathway underlying the carbon flux from plants to the AM mycelium-associated PSB, and the PSB assimilated the photosynthates exuded by the fungus and promoted mineralization and turnover of organic P in the soil.
authors.affiliation: College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, PR China.
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.affiliation: College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, PR China.
authors.forename: Ning
authors.initials: N
authors.lastname: Shi
authors.affiliation: College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, PR China.
authors.forename: Rongfeng
authors.initials: R
authors.lastname: Jiang
authors.affiliation: College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, PR China.
authors.forename: Fusuo
authors.initials: F
authors.lastname: Zhang
authors.affiliation: College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, PR China fenggu@cau.edu.cn.
authors.forename: Gu
authors.initials: G
authors.lastname: Feng
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000378:metabolism*; D018533:Biomass; D050260:Carbohydrate Metabolism / Q000187:drug effects; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D006863:Hydrogen-Ion Concentration; D025301:Hyphae / Q000187:drug effects / Q000254:growth & development; D007553:Isotope Labeling / Q000379:methods*; D038821:Mycorrhizae / Q000502:physiology; D010710:Phosphates / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism; D010802:Phylogeny; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D012150:Polymorphism, Restriction Fragment Length; D012335:RNA, Ribosomal / Q000235:genetics; D017693:Sodium Bicarbonate / Q000494:pharmacology; D012987:Soil; D012995:Solubility; D003313:Zea mays / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology
chemical_list: D002247:Carbon Isotopes; D010710:Phosphates; D012335:RNA, Ribosomal; D012987:Soil; D002245:Carbon Dioxide; D010758:Phosphorus; D017693:Sodium Bicarbonate
keywords: 13CO2 pulse labeling; AM fungus; hyphosphere; maize; organic phosphate; phosphate-solubilizing bacteria (PSB).