Open AccessActivity, size and structure of a Nitrobacter community as affected by organic carbon and nitrite in sterile soil
Author(s) -
Degrange Valérie,
Lensi Robert,
Bardin René
Publication year - 1997
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/j.1574-6941.1997.tb00433.x
Subject(s) - nitrobacter , nitrite , biology , autotroph , nitrification , botany , nitrate , food science , microbiology and biotechnology , bacteria , chemistry , ecology , nitrogen , genetics , organic chemistry
Nitrobacter is the most common nitrite‐oxidizing genus isolated from natural environments. In soil, several Nitrobacter strains can coexist. It is now well known that in pure cultures these strains are able to use organic carbon for their growth with highly variable efficiencies. Our purpose was to examine the role of nitrite or organic carbon as factors governing the evolution of the structure, the density and the activity of a Nitrobacter community in soil. This study has been performed on a recreated nitrite‐oxidizing community consisting of 3 Nitrobacter strains co‐inoculated into sterile soil and differing in their metabolic potentialities: a preferentially autotrophic strain ( N. agilis strain AG), a preferentially mixotrophic strain ( Nitrobacter genomic species 2 strain LL) and a preferentially heterotrophic strain ( N. hamburgensis strain X14). Whatever the enrichments performed (0.271 or 1.353 mg NO 2 − ‐N g −1 dry soil or 1 mg sodium acetate g −1 dry soil), we observed a first phase of multiplication of the total Nitrobacter cells until day 7 or 15, and then, a stabilization of the community until the end of the experiment (day 48). The growth and level of stabilization of this Nitrobacter community as well as the competition between strains in the first phase were predominantly controlled by soil nitrite concentration, resulting in a dominance of the more autotrophic strains. The stabilization of the community resulted from a drastic decrease in nitrite‐oxidation activity due not only to a direct nitrite limitation but also probably to a limiting O 2 effect of the cells' ability to utilize nitrite. The competition was then predominantly monitored by strains' ability to utilize organic carbon for aerobic or anaerobic respiration. The autotrophy/heterotrophy shift strongly modified the result of the competition obtained at the end of the growth stage by inducing drastic declines of the more autotrophic strain and allowing continuous growth of the more heterotrophic strain. This suggests that heterotrophy being more tolerant than autotrophy to environmental changes, organic carbon could be a more permanent structuring factor of the Nitrobacter community than nitrite in soil.