Isolation and Identification of Indigenous Nitrifying Bacteria from Eutrophicated Lake Sediments

Abstract

Introduction: Eutrophication or nutrient pollution is a process in which the natural processes of ecosystems are altered by biogeochemical changes, leading to water degradation. Excess nitrogen in the form of ammonia and nitrate accelerates the onset of eutrophic conditions in water. In the present investigation, nitrifying bacteria were isolated from eutrophied lakes in Tarikere Taluk, Karnataka, India, and identified through morphological and molecular analyses. Water and sediment samples were collected from Duglapura and Hirekathur lakes in Tarikere Taluk in the Shimoga district of Karnataka, India, and nitrifying activity was established only in the sediment samples of Duglapura Lake. The isolation and enrichment of nitrifying bacteria were carried out using an ammonium medium with phenol red as a pH indicator. The change in the color of the pH indicator showed that ammonium was converted to nitrate by nitrite formed through the nitrification process, which was confirmed through the Griess–Ilosvay test. Microscopic examination revealed that the isolate was a gram-negative, rod-shaped bacterium. 16S rRNA gene sequencing showed that the isolate Achromobacter xylosoxidans strain SHB Clp 16S ribosomal RNA gene was identified with a partial sequence. These heterotrophic nitrifying bacteria play a significant role in the indigenous microbial community, contributing to nitrogen cycling in the sediments of eutrophied lake ecosystems. Hence, this study forms a foundation for further research in identifying the nitrogen removal efficiency of the native population of nitrifying bacteria, and thereby the utilization of the native population of nitrifying bacteria in lake sustainability and management through efficient lake restoration.