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-Bacstain- series offer several kinds of bacterial fluorescence staining dye and can be applied for microbial cell viability assay in different principles. Propidium iodide (PI) is an ethidium bromide analog that emits red fluorescence upon intercalation with double-stranded DNA. Though PI does not permeate viable cell membranes, it passes through injured cell membranes and stains the nuclei. PI is often used in combination with a fluorescein compound, such as CFDA, for simultaneous staining of viability and membrane injury.

Kit contents

PI aqueous solution (25 μl×4, 1 mg/ml)


Store at ≤ -20°C

Required Equipment

  • Fluorescence microscope (blue or green excitation light, red emission filter) or Flow cytometer (488 nm or 533 nm laser, red emission filter)
  • Micropipette (20 μl, 1,000 μl)


  • This kit includes microtubes containing solutions. Since there is a possibility that the droplets might attach to the inside walls or caps, please shake them down prior to open.

Staining procedure

  1. Allow PI solution to stand at room temperature for 30 minutes for thawing. Solution should be protected from light a).
  2. Resuspend the organisms with PBS(-) or saline and adjust the number of cells to 106 cells/ml (flow cytometry) or 108 -109 cells/ml (microscopy).
  3. Add 1 μl of PI solution into the 1 ml of microbial cell suspension and vortex gently to mix.
  4. Incubate the microbial cells at room temperature for 5 minutes.
  5. Analyze the stained cells by flow cytometer or under a microscope.

a) Since PI may be carcinogenic, please be careful in its handling/disposing. 

Number of Tests possible

This kit can perform at least 100 tests for the flow cytometric assay and the microscopic assay by following the protocol described herein.


-Bacstain- CFDA solution and -Bacstain- DAPI solution can be applied for double-staining examination with -Bacstain- PI solution.

Double-staining of S.epidermidis

Double-staining of E.coli

Double-staining of S.epidermidis


  1. N. Yamaguchi and M. Nasu, " Flow cytometric analysis of bacterial respiratory enzymatic activity in the natural aquatic environment ", J. Appl. Microbiol., 1997, 83, 43.

Relevant products

-Bacstain- CTC Rapid Staining Kit (for Flow cytometry)
-Bacstain- CTC Rapid Staining Kit (for Microscopy)

CTC has been used by many researchers to evaluate the microbial respiratory activity.
-Bacstain- CTC Rapid Staining Kit allows quick and high-sensitivity CTC-staining.

Right-image : without enhancing reagent
Left-image : with enhancing reagent

Ex filter : Blue
Em filter: Red


CTC staining efficiencies were compared in with or without enhancing reagent condition.


-Bacstain- CFDA solution

CFDA is widely used as an indicator for the measurement of esterase activity.
-Bacstain- CFDA solution is provided as Ready-to-Use DMSO solution.
Fluorescent carboxyfluorescein is produced from non fluorescent CFDA by the esterase in the microbial cell.


-Bacstain- DAPI solution , AO solution

DAPI and AO are nucleic acid staining dyes and can be applied for bacteria either with membrane impairment or with intact membrane.


Products Code Maximum Ex/Em(nm) Number of assays
CTC Rapid Staining Kit (for Flow cytometry) BS01 430, 480/630 100
CTC Rapid Staining Kit (for Microscopy) BS02 430, 480/630 100
CFDA solution BS03 493/515 100
DAPI solution BS04 360/460 100
AO solution BS05 420-460/630-650(ssDNA) 100
PI solution BS07 530/620 100

These products were developed by joint-research with Fukuoka Industrial Technical Center in Japan.

BS07: -Bacstain- PI solution
Revised Sep., 25, 2023