[illumanat'i]

if you've already dealt with it, good, other wise, here's my three cents:

get one or two people, maybe the team leader(s) to take the negative people aside, one by one, as if everything was normal, and tell them they have to stop being so self-centered and negative... the trick, as i have learned, (and it normally works) is to act cool, as if it didn't really matter, its just a suggestion....
if they still are bad, tell them to look up or leave