Cell growth and chaining morphology of viable knockouts. (A) Growth rate versus length expressed in number of diplococcal units. Both values are relative to the original R6 strain. The controls ΔlytA (green square) and ΔlytB (rose square) are also shown. (B) Photograph panel of representative knockout specimens that tend to grow as short or long chains. Only deletion mutants without significant growth delays are shown. Bar represents 2 μm.