An Acidophilic and a Neutrophilic Nitrobacter Strain Isolated from the Numerically Predominant Nitrite-Oxidizing Population of an Acid Forest Soil

Abstract

Two physiologically and serologically distinct strains of chemoautotrophic nitrite-oxidizing bacteria were isolated as numerically predominant members of the nitrite-oxidizer population of an undisturbed forest soil with a pH range of 4.3 to 5.2. One isolate responded as a neutrophile, characteristic of the family Nitrobacteraceae, and cross-reacted strongly with fluorescent antibody to Nitrobacter strain Engel. The second isolate responded as an acidophile in pure culture, demonstrated maximal nitrite oxidation activity at pH 5.5, and had a pH tolerance range of pH 4.1 to 7.2. Nitrite oxidase in whole cells of the acidophile sustained activity to at least pH 3.5. Cell morphology of both strains typified the genus Nitrobacter in all respects when cultured at pH 7. However, under more acidic conditions the acidophile tended to elongate and at times appeared to branch. These data provide the first evidence for the existence of an acidophilic chemoautotrophic nitrifying bacterium. Isolation of the neutrophilic Nitrobacter strain reported here complements the earlier isolation of a neutrophilic Nitrosospira strain to provide further evidence of a prominent acid-intolerant population of chemoautotrophic nitrifiers in this acid forest soil.

Role of the terrestrial subsurface in shaping geothermal spring microbial communities

“…In fact, a number of previous studies have isolated microbes from habitats whose physical parameters lie clearly outside their temperature and/or pH optimum (e.g. Hankinson and Schmidt, 1988;Zakalyukina et al, 2004;Ellis et al, 2008). These findings support the idea that hardy microbes can persist in unsuitable environments for long periods of time, perhaps in a dormant state.…”

Influence of Ammonium: Nitrate Ratio and Nitrogen Concentration on Nitrification Activity in Soilless Potting Media

“…The assay conditions for determining NH 4 oxidation rates in this study were performed using a pH 7.0 buffer. Consequently, any organisms that oxidize NH 4 better at lower pHs, such as selective heterotrophs (Lang and Jagnow, 1986;Tate, 1977;Verstraete and Alexander, 1972) or acidophillic autotrophs (Hankinson and Schmidt, 1988), which do not tolerate high pH levels, would not have been detected in this study. In summary, medium type, N fertilizer rate and formulation, and the presence of plants strongly influenced the nitrifying activity of soilless potting media.…”

Effects of the insecticide endosulfan on nitrification in low pH agricultural soils

“…Nitrification is still evident at pH 5.0 in many soils and the pH optima for nitrification in some acid soils may be as low as 4.5 (Haynes, 1986). This has often been shown to be due to heterotrophic nitrification (Lang and Jagnow, 1986), although autotrophic nitrifiers have been isolated from soil with pH values as low as 4.3 (Hankinson and Schmidt, 1988). Most research on nitrification in acid soils has concentrated on forest systems (e.g., Adams, 1986; Hankinson and Schmidt, 1988) and data for agricultural soils are limited.…”

“…This has often been shown to be due to heterotrophic nitrification (Lang and Jagnow, 1986), although autotrophic nitrifiers have been isolated from soil with pH values as low as 4.3 (Hankinson and Schmidt, 1988). Most research on nitrification in acid soils has concentrated on forest systems (e.g., Adams, 1986; Hankinson and Schmidt, 1988) and data for agricultural soils are limited. In a recent study of nitrification in Atlantic coastal plain soils appreciable nitrifying activity was observed in some soils with a pH of 4.5-4.6 (Weier and Gilliam, 1986).…”