Nitrate reduction by fungi in marine oxygen-depleted laboratory microcosms

Abstract

Fungi are major contributors to the process of denitrification in terrestrial environments, but their role as denitrifiers in the ocean has not been addressed thus far. We measured the nitrate reducing capacity of fungi based on the respiratory electron transport system (ETS) activity and nitrite accumulation in oxygen-depleted laboratory microcosms. Specific fungal and bacterial activity in these microcosms was studied by fortifying the sediments with antibiotics and anti-fungal compounds, respectively. The higher ETS activity in the microcosm with antibiotics indicated higher fungal than bacterial activity. Activity of two fungi, # An-2 (MTCC Accession number 9376) and # MT-811 (JMC Accession number 11502) in pure cultures under aerobic and anaerobic conditions, and in the microcosms was also studied. ETS activity in the fungal cultures grown under anaerobic conditions was half the activity measured under aerobic growth conditions. Simulated laboratory microcosm data show that fungi participate in the denitrification activity in sediments from marine hypoxic environment.