The vial which has been frozen in the freezer may get contaminated outside of it, so I still don't need to sterilize the outside of it before using?
well i use a tissue "wetted" by detergent and gently wash the tube.
When i have opened the cap, the opening may be contaminated too. Should i not wipe it with something before recapping it?
I don't do that and as you thaw cells on ice and put the vial back to -80° just after picked your cells i don't think that allows growth contamination. Moreover, stripping bacterias on plate will reduce contamination if there is one. But you must add selection pressure in your culture. And there is less risk of contamination in the vial than in the culture, isn't it? Moreover, i made two aliquots in the first time. One that i never open before getting problem with the working-vial.
Should the cells be completely thawed before making the streaks on the agar plate?
That's better but not completely necessary
but please correct me if i'm wrong
What should i do with the rest of the thawed cells, since i only make some streaks on the agar plate?
back to -80°C!
hope i've clarified situation