Before revision:  The most remarkable finding from our studies is that , for a given cargo size, the swim-speed is maximized when the rotational drag coefficient of the flagella is tuned to the torque-speed  characteristics of the bacterial flagellar motor .
After revision:  The most remarkable finding from our studies is that , for a given cargo size, the swim-speed is maximized when the rotational drag coefficient of the flagella is tuned to the torque-speed characteristics of the flagellar motor is not considered in Purcell's original analysis. Here we derive a tuned condition representing a match between the flagella geometry and the torque-speed characteristics of the bacterial flagellar motor .