Open AccessCultivation and characterization of thermophilic N itrospira species from geothermal springs in the US G reat B asin, C hina, and A rmenia
Author(s) -
Edwards Tara A.,
Calica Nicole A.,
Huang Dolores A.,
Manoharan Namritha,
Hou Weiguo,
Huang Liuqin,
Panosyan Hovik,
Dong Hailiang,
Hedlund Brian P.
Publication year - 2013
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 - 10.1111/1574-6941.12117
Subject(s) - nitrospira , nitrite , biology , nitrate , thermophile , environmental chemistry , ecology , bacteria , chemistry , genetics
Despite its importance in the nitrogen cycle, little is known about nitrite oxidation at high temperatures. To bridge this gap, enrichment cultures were inoculated with sediment slurries from a variety of geothermal springs. While nitrite‐oxidizing bacteria ( NOB ) were successfully enriched from seven hot springs located in US G reat B asin, south‐western C hina, and A rmenia at ≤ 57.9 °C, all attempts to enrich NOB from > 10 hot springs at ≥ 61 °C failed. The stoichiometric conversion of nitrite to nitrate, chlorate sensitivity, and sensitivity to autoclaving all confirmed biological nitrite oxidation. Regardless of origin, all successful enrichments contained organisms with high 16 S r RNA gene sequence identity (≥ 97%) with N itrospira calida . In addition, Armenian enrichments also contained close relatives of N itrospira moscoviensis . Physiological properties of all enrichments were similar, with a temperature optimum of 45–50 °C, yielding nitrite oxidation rates of 7.53 ± 1.20 to 23.0 ± 2.73 fmoles cell −1 h −1 , and an upper temperature limit between 60 and 65 °C. The highest rates of NOB activity occurred with initialNO 2−concentrations of 0.5–0.75 mM; however, lower initial nitrite concentrations resulted in shorter lag times. The results presented here suggest a possible upper temperature limit of 60–65 °C for N itrospira and demonstrate the wide geographic range of N itrospira species in geothermal environments.