title: Sphingomonas sp. is a novel cell culture contaminant.
abstract: A novel contaminant was isolated from Madin Darby Bovine Kidney (MDBK) cells. The organism was unable to grow on standard microbiological media by conventional techniques, but grew well in Dulbecco's Modified Eagle's Medium (DMEM) containing high glucose concentration. The organism formed a white biofilm on the bottom without any signs of turbidity. Upon genome sequence analysis of 16 S rDNA, the contaminant was identified as Sphingomonas sp. Shah, a member of the group α-Proteobacteria. Neutral red dye uptake method confirmed clear cytotoxic potential of the bacterium on A-549 cells. The organism was capable of invading and infecting different mammalian cell lines: MDBK, ZZ-R, 293-T, A549, and HeLa cells. Infected cells showed a variety of cytopathic effects including vacuolation at perinuclear area, cytoplasmic granulation and membrane blebbing. Microscopic analysis of the infected cells revealed the presence of cytoplasmic vacuoles harboring motile organisms. Apparently local serum preparations seem to be the source of this contamination, which is imperceptibly passed on from one culture passage to the other and ultimately leading to serious cytopathic manifestations.
authors.affiliation: School of Biological Sciences, University of the Punjab, Quaid-i-Azam Campus, Lahore, 54590, Pakistan.
authors.forename: Muhammad Tahir
authors.initials: MT
authors.lastname: Asghar
authors.forename: K
authors.initials: K
authors.lastname: Al-Ghanim
authors.forename: Shahid
authors.initials: S
authors.lastname: Mahboob
authors.forename: Muhammad
authors.initials: M
authors.lastname: Sharif
authors.forename: Jawad
authors.initials: J
authors.lastname: Nazir
authors.forename: Abdul Rauf
authors.initials: AR
authors.lastname: Shakoori
mesh_terms: D000818:Animals; D002417:Cattle; D018929:Cell Culture Techniques / Q000379:methods*; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008875:Middle Aged; D020578:Sphingomonas / Q000166:cytology* / Q000302:isolation & purification*
keywords: ALPHA-PROTEOBACTERIA; APOPTOSIS; CELL CULTURE CONTAMINANT; CYTOPATHIC EFFECTS; HeLA CELLS; MDBK CELLS; MEMBRANE BLEBBING