Optimal stride frequency in running is typically much lower than optimmal cadence for cycling. It is commonly seen that runners who convert to cycling ride in a larger gear and a lower cadence than experienced cyclists. Riding at a high cadence required the muscles of the cyclist to be recruited and contracted precisely in order to maintain a smooth pedal stroke. This takes time to develop, since the cerebellum (portion of the brain responsible for motor control) is slow to adapt to new patterns.
Unfortunately, riding in a big gear with a slow cadence places stresses on the joints (primarily the knees) that can lead to pain and joint dysfunction. For this reason, it is important to try to increase your cadence until it reaches about 80 r.p.m.
I would recommend that you vary your cadence during your commute. Try doing short stretches where you ride at as high of a cadence as you feel comfortable while working to maintain a smooth pedal stroke. Increase your cadence by lowering gears until you feel youself bouncing on the saddle, then back off a bit until you are smooth again. Then return to your more comfortable slow cadence for a couple of minutes and repeat the drill.
You will accomplish several things by doing this during your commute. First, you will increase your natural cadence in time, which is good. Second, you will add variety to your riding which will keep your commute fresh and fun.
Congratulations to you for working to keep less cars on the road and use your body to travel your commue! Have fun and be safe!