Well, not true actually.
Morgan Stanley, Merrill, Lehman Ratings Cut by S&P (Update3) - Bloomberg
And....um....Merrill Lynch has at no time ever, in history, gone 'bankrupt' . On the day Lehman filed, the Bank of America acquisition was announced.
Nope. The rating itself was cut. Not just a negative outlook
Teakdoor clearly isn't the place to find out facts on this scenario !