Fungi of a forest soil nitrifying at low pH values

Abstract

No autotrophic nitrifying organisms were found in a podzolic brown earth forming nitrate. 350 fungi and aerobic heterotrophic bacteria were isolated from this soil and examined for their nitrifying abilities. About one quarter of the isolates produced 0.05–0.90 mg N·1−1 nitrite or nitrate in peptone solution, soil extract mixture or sterilised soil. The nitrification rate of the most active fungus, Verticillium lecanii, was highest at pH 3.5 in defined media. The results support the significance of heterotrophic nitrification in acid soils.

Review of Biohydrometallurgical Metals Extraction from Polymetallic Mineral Resources

“…Sulfuric and sulfurous acids are produced by Acidithiobacillus species as well as Thiothrix, Beggiatoa [56] and some fungi [57]. Nitric and nitrous acids are produced by ammonia and nitrite oxidising organisms, heterotrophic nitrifying organisms and some fungi [58][59][60]. Carbonic acid is the end product of energy metabolism when carbon dioxide reacts with water but it is a weak acid and unlikely to contribute greatly to mineral dissolution with the exception of carbonate minerals [55].…”

Nitrification in Dutch heathland soils

“…Therefore, nitrifying activities of many of these micro-organisms may also be restricted to micro-sites of neutral pH (Stroo et al 1986). However, some chemo-organotrophic bacteria and fungi have been reported to produce nitrate in media of pH <5 (Lettl 1985;Stroo et al 1986;Lang and Jagnow 1986).…”

“…Nitrate production in acid soils that seem to lack chemolithotrophic nitrifying bacteria, as quantified by the Most Probable Number technique, is often believed to be the result of chemo-organotrophic micro-organisms (Ishaque and Cornfield 1976;Tate III 1977;Lang and Jagnow 1986;Kuenen and Robertson 1987). However, this interpretation is questionable as the Most Probable Number technique, has been developed for the enumeration of chemolithotrophic nitrifiers in agricultural soils of neutral pH (Schmidt and Belser 1982).…”

“…Until recently, all known chemolithotrophic nitrifiers were sensitive to a low pH (Chapter 1). It has been assumed that heterotrophic micro-organisms are the most important nitrifiers in acid soils where no chemolithotrophic nitrifiers could be detected and where specific inhibitors of chemolithotrophic nitrification had little influence on the formation of nitrate (Adams, 1986ab;Lang and Jagnow, 1986;Stroo et al, 1986;Killham, 1986). However, there are acid soils in which nitrification seems to be chemolithotrophic (Weier and Gilliam, 1986;Killham, 1986).…”

“…In the different soils that have been investigated, either heterotrophic or chemolithoautotrophic micro-organisms are thought to be responsible for the observed nitrification (Adams, 1986ab;Weier and Gilliam, 1986;Killham, 1986). Recently, heterotrophs were isolated which can nitrify in liquid media at low pH (Lang and Jagnow, 1986;Stroo et al, 1986). On the other hand, with the exception of an acidtolerant nitrite-oxidizing Nitrobacter strain described by Hankinson and Schmidt (1988), all chemolithotrophic nitrifiers that have been isolated from acid soils were not able to oxidize nitrogen at pH < 5.5 in a liquid medium (Hankinson and Schmidt, 1984;Martikainen and Nurmiaho-Lassila, 1984).…”