Aerobic granules: microbial landscape and architecture, stages, and practical implications

Area of Science:

• Microbiology
• Environmental Engineering
• Biotechnology

Background:

• Aerobic granules are crucial for wastewater treatment, requiring specific microbial communities.
• Understanding granule formation and architecture is key to optimizing their application.
• Existing models often simplify granule structure, lacking detailed insights into internal complexities.

Purpose of the Study:

• To investigate the detailed structural characteristics of aerobic granules using novel imaging techniques.
• To provide a deeper understanding of granule formation and internal architecture.
• To generate data for validating complex granule formation models.

Main Methods:

• Developed and applied new imaging approaches to visualize aerobic granule structure.
• Utilized staining techniques to enhance image contrast and overcome thresholding limitations.
• Generated three-dimensional reconstructions of granule interiors, revealing internal channels and cavities.

Main Results:

• Revealed a complex, cavernlike interior with detailed channels and dead-end paths.
• Observed large cavities in mature granules facilitating microbial colony growth.
• Found paradoxically higher biomass content in granule interiors in some cases.
• Identified microbial clusters suggesting growth primarily through biomass outgrowth, not particle aggregation.

Conclusions:

• Aerobic granules possess intricate internal structures that significantly influence their function.
• Granule growth is predominantly driven by biomass outgrowth from the interior.
• The detailed structural insights and generated grids can validate and refine computational models of granule formation.