Abstract:

The Winogradsky column, a classic experimental model, is widely used to study microbial ecology, metabolic diversity, and nutrient cycling in sedimentary environments. It provides a self-sustaining system where distinct microbial layers form based on oxygen, light, and nutrient gradients. Among the critical nutrients influencing microbial growth and composition, nitrogen—especially in the form of urea—plays a central role in microbial metabolism and ecosystem dynamics (Duppala & Kaladhar, 2019) [13]. Urea is a nitrogen-rich compound commonly found in agricultural runoff and wastewater, where it can alter microbial community structures and inhibit sensitive microbial populations.
This study investigates the effect of urea on microbial isolates obtained from different layers of a Winogradsky column, using the Minimum Inhibitory Concentration (MIC) method to determine tolerance thresholds. Isolates included cyanobacteria, green sulfur bacteria, and sulfate-reducing bacteria (SRB), each with distinct ecological functions. Serial dilutions of urea (0.1 to 5.0 mg/mL) were prepared, and growth inhibition was measured through optical density and colony count analyses following CLSI (2021) [8] microbroth dilution protocols.
The study underscores the importance of nitrogen management in aquatic and soil ecosystems, as excessive urea can shift microbial populations and affect nutrient cycling processes. Applying the MIC method in an ecological context bridges microbiological and environmental science, providing a quantifiable approach to assess chemical impacts on microbes. This research contributes to the understanding of nitrogen stress in microbial systems and its ecological implications.
 

Keywords:

Winogradsky column, urea, Minimum Inhibitory Concentration (MIC), microbial ecology, cyanobacteria, sulfate-reducing bacteria (SRB), green sulfur bacteria, nitrogen metabolism, environmental microbiology, microbial isolation, nutrient cycling, Gram staining, microbial sensitivity, biogeochemical gradients, stratified microbial ecosystems

Aim/Objectives

Methods