Peter Luykx writes:
Here's a speculation: the inability to grow with stirring is most immediately
an effect of a deficient CELL WALL rather than directly owing to a fragile
plasma membrane itself...
This is certainly possible. But here are some more details: the colonies are
smaller on agar, but they look the same as wild type; the cell wall may
be affected, but it is not severely damaged, because the cells are still
difficult to grind up for protein preps.(the wild type is a small, very
tough cell with unknown cell wall composition.) This seems to indicate that
the cell wall is not the source of the fragility, although it could be damaged
in such a way that causes physiological problems, while not actually
disrupting the wall structure completely.