Consumption of NO and other N-cycle intermediates by strain T-27.

Bacteria affiliated with the phylum Gemmatimonadetes are found in high abundance in many terrestrial and aquatic environments, yet little is known about their metabolic capabilities. Difficulty in their cultivation has prompted interest in identifying better growth conditions for metabolic studies, especially related to their ability to reduce NO, a potent greenhouse gas. T-27 is one of few cultivated strains of Gemmatimonadetes available for physiological studies. Our objective was to test this organism's ability to use nitrite, nitrate, and NO, and mineral forms of assimilable NH at concentrations not typically used in tests for compound utilization. Cultures incubated under anaerobic conditions with nitrate, nitrite or NO failed to grow or show depletion of these substrates. Nitrate and nitrite (1 mM) were not used even when cells were grown aerobically with the O allowed to deplete first. NO reduction only commenced in the presence of O and continued to be depleted when refed to the culture under anaerobic, microaerobic and aerobic atmospheres. Carbon mineralization was coupled to the electron-accepting processes, with higher reducing equivalents needed for NO utilization under aerobic atmospheres. NO was reduced to N in the presence of 20% O, however the rate of this reaction is reduced in the presence of high O concentration. This study demonstrated that T-27 possesses unique characteristics for assimilative and dissimilative N processes with new implications for cultivation strategies to better assess the metabolic abilities of Gemmatimonadetes.