Isolation and characterization of a Gram-positive polyphosphate-accumulating bacterium

Area of Science:

• Microbiology
• Environmental Science
• Biotechnology

Background:

• Biological phosphorus removal is crucial for wastewater treatment.
• Polyphosphate-accumulating organisms (PAOs) are key players in this process.
• Identifying novel PAOs enhances understanding and efficiency of phosphorus removal.

Purpose of the Study:

• To isolate and characterize a novel Gram-positive, polyphosphate-accumulating bacterium from activated sludge.
• To investigate the phosphate uptake capabilities and physiological features of the isolate.
• To identify the isolate and assess its potential contribution to phosphate removal.

Main Methods:

• Isolation of bacteria from activated sludge using pyruvate-supplemented agar.
• Microscopic observation and toluidine blue staining for polyphosphate granules.
• Phosphate uptake experiments under anaerobic/aerobic conditions with different carbon sources.
• Phylogenetic analysis and biochemical characterization.

Main Results:

• A Gram-positive, oval to coccobacilli bacterium was isolated and identified as Tetrasphaera elongata.
• The isolate demonstrated rapid phosphate uptake (9.2 mg-P/g-dry weight) after anaerobic incubation with casamino acids.
• Phosphate removal was not observed when acetate was the sole carbon source, and its efficiency was lower than Microlunatus phosphovorus.
• Phylogenetic analysis confirmed the isolate as T. elongata, a species recently proposed for activated sludge.
• The predominant isoprenoid ubiquinone was menaquinone (MK)-8(H(4)), suggesting a significant role in phosphate removal.

Conclusions:

• Tetrasphaera elongata was successfully isolated and identified from activated sludge.
• The isolate possesses polyphosphate accumulation and phosphate uptake capabilities, contributing to biological phosphorus removal.
• The presence of menaquinone (MK)-8(H(4)) highlights its potential significance in phosphate-removing activated sludge ecosystems.