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A Dilute Medium to Determine Population Size of Ammonium Oxidizers in Forest Soils
Author(s) -
Donaldson Jennifer M.,
Henderson Gray S.
Publication year - 1989
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1989.03615995005300050056x
Subject(s) - soil water , autotroph , incubation , ammonium , nitrification , most probable number , nitrate , environmental chemistry , chemistry , oxidizing agent , heterotroph , diluent , population , bacteria , nitrogen , ecology , biology , nuclear chemistry , biochemistry , genetics , demography , organic chemistry , sociology
Incubation experiments using soils from mixed oak ( Quercus sp.) stands showed accumulation of nitrate but standard most probable number (MPN) assays showed no NH 4 ‐oxidizing bacteria were present. This led to a preliminary conclusion that nitrification in these soils must be heterotrophic. However, further incubation studies indicated that NH 4 ‐N concentrations in standard MPN medium were too high for autotrophic NH 4 oxidizers that are adapted to soils with low NH 4 ‐N levels and exhibit low activities. Therefore, media with lower NH 4 ‐N concentrations were tested against the standard MPN medium. Each medium was tested using both 1 m M phosphate buffer and deionized water as diluent to examine responses to small changes in buffer capacity. A 0.1 × medium used with deionized water diluent was found to best estimate populations of low‐activity NH 4 ‐oxidizing bacteria present in soils with low NH 4 ‐N concentrations.