Seasonal variations of nitrate reducing and denitrifying bacteria utilizing hexadecane in Mandovi estuary, Goa, West Coast of India

Abstract

Mandovi estuary has a prolific population of heterotrophic bacteria due to the influx of nutrients including nitrate and organic hydrocarbons. Seasonal sampling at various locations along the estuary was carried out to isolate nitrate reducing and denitrifying bacteria capable of hexadecane utilization. Total viable counts of nitrate utilizing bacteria showed variations with seasonal changes. It ranged from 103-106 cfu/mL on nitrate reduction medium and 101-105 cfu/ml on minimal media containing hexadecane as the sole carbon source. Highest bacterial counts were obtained during the monsoons. 22 percent of bacteria capable of hexadecane utilization were nitrate reducing and 12 percent were denitrifying. 29 percent of the hexadecane utilizing cultures isolated during the monsoons exhibited nitrate reducing activity. However, seasonal variations did not affect the frequency of the denitrifying hexadecane utilizers.