Organisms of the Nitrogen Cycle Under Extreme Conditions: Low Temperature, Salinity, pH Value and Water Stress

Publisher Summary This chapter provides a general understanding of the importance of the denitrification and other reactions of the N-cycle in these environments to global ecology, the principles governing their activities and ongoing adaptations that enable the microbes to thrive in such environments. To survive at low T, microbes can reduce their cell size and their capsular polysaccharide coat thickness; they can also change their fatty acid and phospholipid composition. The unfrozen microsites, surrounded by ice, have limited gas exchange, which leads to the development of O 2 deficiency thereby, favoring denitrification. Most of the studies exploring gas emissions from soil at low T have focused on the periods of soil thaw, when peaking emission rates can be observed. Finally, the T responses of N 2 O production and reduction rates might significantly differ among different soil types depending upon the composition of the microbial communities. The term “halophile” includes organisms that require NaCl or another salt for growth (“salt-resistant organisms”) and those which thrive in both non-saline and saline habitats. The chapter gives a description of halophilic environment. The aerobic halophilic Archaea of the family Halobacteriaceae are the halophiles par excellence. Extreme halophilic and non-salt-tolerant bacteria are found site-by-site at all salt concentrations in the soil. The chapter lists the most representative prokaryotic denitrifiers described from halophilic environments and covers the relationship between soil pH and denitrification.