Rapid estimation of microbial numbers in water using bulk fluorescence

Area of Science:

• Environmental microbiology
• Analytical chemistry

Background:

• Accurate enumeration of microbial cells is crucial for microbial ecology and water quality assessment.
• Traditional methods like culturing can be time-consuming and may not capture all viable cells.
• Existing non-culturing methods may lack sensitivity for low microbial concentrations found in environmental waters.

Purpose of the Study:

• To develop and validate a rapid, sensitive, and cost-effective method for quantifying microbial cells in various water types without culturing.
• To compare the performance of the new method against established techniques.

Main Methods:

• Utilizing bulk fluorescence with SYBR Gold DNA stain for microbial cell quantification.
• Employing single-cell and 96-well plate fluorescent spectrophotometers.
• Investigating the effect of DNase I treatment to reduce background noise from free DNA.

Main Results:

• Bulk fluorescence accurately quantifies microbial cells (cells/mL) in fresh, marine, and estuarine waters.
• The method is sensitive to concentrations greater than 10^5 cells/mL, suitable for environmental samples.
• Precision of bulk fluorescence exceeded that of epifluorescent microscopy, with discernible differences of approximately 10^5 cells/mL.
• DNase I treatment enhanced sensitivity by reducing background noise.

Conclusions:

• Bulk fluorescence with SYBR Gold is a simple, rapid, and inexpensive technique for microbial enumeration in water.
• This method is adaptable for automated analysis and provides a valuable tool for microbial ecology and water quality monitoring.
• The enhanced sensitivity and precision make it superior to traditional microscopy for environmental samples.