[Factors affecting the DAPI fluorescence direct count in the tidal river sediment].

Area of Science:

• Environmental Microbiology
• Analytical Chemistry

Context:

• Tidal river sediments harbor diverse microbial communities.
• Accurate bacterial enumeration is vital for assessing aquatic ecosystem health.
• The DAPI (4', 6-diamidino-2-phenylidole) fluorescence direct count is a common method for bacterial quantification.

Purpose:

• To investigate factors influencing the DAPI direct count in tidal river sediment.
• To optimize the DAPI staining procedure for enhanced accuracy.
• To identify key sediment properties affecting bacterial enumeration.

Summary:

• An optimized DAPI staining protocol involving 2000-fold dilution, 10-minute ultrasonic water bath, 10 microg/mL DAPI concentration, and >30 minutes staining time yielded optimal results.
• Bacterial numbers correlated with the proportion of non-nucleoid-containing cells (r=0.587, p=0.004).
• Organic matter and clay content significantly influenced bacterial counts, with clay strongly correlating with organic matter.

Impact:

• Provides an optimized DAPI staining method for tidal river sediments.
• Highlights the importance of considering sediment characteristics (organic matter, clay content) for accurate bacterial quantification.
• Enhances the reliability of DAPI direct counting in environmental samples.