1999 Volume 14 Issue 1 Pages 19-22
Acridine orange direct count (AODC) of bacterial community was examined with two types of epifluorescence microscope, BX-60 (OLYMPUS OPTICAL CO., LTD.) and BHS-RFK (OLYMPUS OPTICAL CO., LTD.). When observed under the naked eye, AO-stained particles appeared clearer under the BX60 than under the BHS-RFK. This difference in the image was considered to influence the AODC containing particles of various size and shape. AODC of a bacterial pure culture did not provide significant difference when determined under the naked eye with these two epifluorescence microscopes. However, the AODC of complex communities from river water and epilithon showed difference in counting among 4 investigators. To clarify the reason for these differences, the particle image of each scope was compared with an image analyzer. Mean AO-stained particle area of BHS-RFK was larger than that of BX60, probably caused by the existence of a dim margin surrounding particles for the former system. As a result, it is not necessary to correct AODC when determined under the naked eye. However, when an image analyzer is employed to determine AODC of natural bacterial community, procedure for application should be checked carefully for newly developed microscope.