Single pan and two proprietory firm - whether 2 gst number required

Mr. X has proprietory firm ('ABC' ) in the business of COAL is already registered under GST  and now simultaneously he want to do other business in the name of ('XYZ') in the business of  Transportation . 

So Mr.A can do business (XYZ) with same GST number  which is already obtained or he will have to obtain new GST Number on same PAN ? 

if Mr. A can do both business with single GST number then how the name of proprietory business and nature of activities will be mentioned ?