EFFECT OF DIFFERENT OSMOLYTES ON BACTERIA AND ARCHAEA AMMONIA OXIDISERS

Abstract

This study is aimed to investigate response of ammonia oxidising archaea (AOA) and ammonia oxidising bacteria (AOB) to different concentrations of NaCl or sorbitol using culture media. It was hypothesized that an increase in concentrations will reduce nitrification activity of AOA and AOB, irrespective of NaCl or sorbitol. Two AOA (Candidatus (Ca.) Nitrosotalea sinensis, Candidatus Nitrosocosmicus franklandus) and AOB (Nitrosomonas europaea (ATCC 19718) and Nitrosospira multiformis (ATCC 25196)) were grown aerobically without shaking in a freshwater medium (FWM) adjusted to seven different concentrations of either NaCl or sorbitol. AOB were incubated at 25^oC while AOA were incubated at 35^oC both in the dark. Aliquots of 100 µl were taken from each sample at 24 hours intervals for 250 hours and analysed for nitrite concentration. Both AOA and AOB responded to changes in NaCl or sorbitol concentrations in the culture media as nitrification activity decreased with an increase in NaCl or sorbitol concentrations in both cultures. AOA were more sensitive to the increase in NaCl or sorbitol concentrations than AOB. Ca. Nitrosotalea sinensis was the most sensitive while N. europaea is the least sensitive ammonia oxidisers to changes in increase in NaCl or sorbitol concentrations. This study confirmed that there were differences in the osmolytes tolerance between AOA and AOB upon exposure to similar concentration of NaCl or sorbitol.