Cell lysis for unknown reasons - (Jul/22/2013 )

I encountered couple of problems culturing BHK, RD and Vero cells,during the last couple of months. In a first time the tree cell lines lysed (apparently still attached to the plate (96-48-24-6 well/plates as wells as the flask) for unknown reasons. Surprisingly, the cells lysed in few wells and not in all. The pH of the cell culture medium appeared correct compared to the culture medium of normal cells.

Recently in 24-well/plate, the pH of the cell culture medium in 4 wells was over 9. The cells in these wells died. Any evidence for problem in the 20 other wells. The cell culture conditions were the same for the 24 wells. In deph analysis suggested that the pH increase in the 4 wells caused the death of the cells. Could any one explain me such a pH change?

During the last week, one day after seeding the BHK cells they became spherique in the majoority of wells (24 wells) with the presence of long and spherique black structures moving in the cell culture medium. microbiology analysis did not reveal the growth of any bacteria in the medium.

Could any one help to understand these issues?

The pH change and cell lysis sounds like a viral infection, where the pH change is due to the decay products of the cells. Typically viruses will wipe out a culture with no other sign of contamination.

There are a number of threads on here about black dots in cell culture, these are most commonly thought to be a species that is found in waterbaths.