An Ultrastructure Observation of Vital/Dead Streptococcus Sanguis Cells

Objectives:To observe the ultrastructure of vital and dead (heat-inactive and chemical-inactive) streptococcus sanguis cells. Methods: Streptococcus sanguis was reconstituted from lyophilized stocks and cultured in tryptic soy broth under anaerobic conditions at 37⁰C for 16-18hrs,then the cells were harvested by centrifugation for 5 min at 8000g,the bacterial pellet was suspended in sterile physiological saline to a density of about 10⁷ -10⁸ cells/ml.Subsequently,a fration of native streptococcus sanguis suspension was kept in 60⁰C water for 30 min to get heat-inactive cells;Another fraction of native streptococcus sanguis suspension was treated by 2% chlorhexidine for 5 mins to get chemical-inactive cells.Then vital/dead(heat-inactive and chemical-inactive)cells was fixed by 2.5% glutaraldehyde for observation under transmission electron microscopy. Results:The vital cell walls were intact,and tightly connected with cell membrane,the plasm was homogeneous,the nuclei were clear;The heat-inactive cell walls were nearly intact,but the nuclei were not clear.The chemical-inactive cell walls were not intact,the plasm flows from cells,some shade cells even appeared.conclusion:The ultrastructure were different between heat-inactive and chemical -inactive cells.