More important - and deserves it own thread probably - is whether after the comma between phrase there should be a space or not
Go read Googles webmaster guidelines - it will tell you everything you need to know - that it doesnt matter one way or the other is fine - the closer you can make it to compliant html the better it is
BTW - there will be people that tell you that keywords dont matter to Google - they dont use them anyway - You have my permission (not that you need it) to yell BS as loud as you can cause they have started using them again