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A method based on plate count for enumerating N 2 O/N 2 ‐producing bacteria from nitrate in the soil
Author(s) -
Allievi Luigi,
Möller Frank
Publication year - 1992
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/jobm.3620320502
Subject(s) - soil water , nitrate , nitrogen , chemistry , biology , ecology , organic chemistry
The production of N 2 and N 2 O from NO 3 ‐N can provoke a loss of nitrogen from agricultural land. However, in the case of excessive nitrate it can avoid water pollution. A method for counting the producers of N 2 and N 2 O from nitrate in soil, based on the isolation of colonies grown on plates prepared for the total aerobe count, was developed and tested. The method can be used to evaluate a soil bacterial group that includes not only denitrifiers but all N 2 O producers from nitrate. Randomly selected colonies are transferred into liquid medium and incubated in the presence of 10% acetylene, and N 2 O production is then determined. Multiplying the fraction of colonies thus detected as N 2 O‐producing by the total aerobe number yields the N 2 O/N 2 producer number. We considered it advisable to consider total aerobe instead of total anaerobe count because the obligate aerobes are prevalent in the soil, and various aerobes, as well as denitrifiers, are N 2 O producers. The new method was compared with a previously developed method based on the most‐probable‐number procedure using three soils, and the former method had the greater precision. The new method was also applied to two other soils. The percentages of N 2 O/N 2 producers ranged in the five soils from 37% to 84% and numbers from 5 to 65 million · g −1 .