Anammox bacteria detected in fish intestinal tract systems

Abstract

Anammox bacteria serve an important ecological role in the global nitrogen cycle, enabling the coupling of ammonium and nitrite to yield dinitrogen gas (N2) under anoxic conditions. Based on PCR amplifications of genomic DNA and analysis of the 16S rRNA gene sequence, anammox bacteria was found in intestinal tracts of two types of fish, Siganus fuscescens and Mugil cephalus. Anammox bacteria identified in these fish belonged to the genera Brocadia and Kuenenia, suggesting that the living conditions of S. fuscescens and M. cephalus were under significant influence of wastewater pollution. Our results showed an association between the existence of anammox bacteria in fish intestinal tracts and sediment- or mud-eating habits of the fish involved. The presence of anammox bacteria in an animal system would provide a more comprehensive understanding on ecophysiological characteristics and distribution of anammox bacteria. This discovery might also provide useful information about the living conditions of fish, serving as an environmental indicator of anthropogenic pollution.