Submitted to: Society of America Microscopy Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/18/2002
Publication Date: N/A
Technical Abstract: Fluid from a characterized continuous flow culture chemostat containing 29 microorganisms was subjected to a low speed centrifugation, 4000 x g, followed by sequential filtration through 0.45 and 0.22um membranes. The sterilized chemostat fluid was then centrifuged for 3h at 150,000 x g, washed in buffer and re-centrifuged. Pellets were either re-suspended in buffer or fixed for ultrastructural evaluation by the addition of a glutaraldehyde fixative. Examination of glutaraldehyde preserved pellets revealed numerous single membrane-bounded vesicles of between 50-100nm in diameter. Vesicles varied with regard to contents and membrane electron density. Re-suspended vesicles were utilized in a bacterial killing assay in which isolates of Salmonella typhimurium and Escherichia coli were incubated with microvesicle suspensions. Bacteria incubated with microvesicle suspensions exhibited a 2 log drop in colony forming units per ml (CFU/ml) within two hours of inoculation while no reduction in CFU/ml was observed in control preparations. These results suggest that the isolated microvesicles are bacteriolytic towards some enteropathogenic bacteria. Bacteriolytic vesicles present in the culture probably result from extrusions of outer membrane from Gram negative bacteria present in the culture.