A devilish Wanderers wicket has continued to favour the bowlers on day two of the third and final Test in Johannesburg.
Replying to South Africa's 303 all out, Australia reached 246-7 when bad light stopped play with 14.4 overs remaining, a deficit of 57 runs.
Brett Lee remains unbeaten on 42 with Michael Kasprowicz yet to score.
Shane Warne (36) and Lee counterpunched with the reliable Mike Hussey in the final session after a combination of Makhaya Ntini and some rash stroke-making had seen the tourists slump to 106-5.
Ntini produced a fearsome opening spell of 4-52 to remove Matthew Hayden (three), Damien Martyn (21), Ricky Ponting (34) and Andrew Symonds (four) in quick succession either side of lunch.
The Proteas paceman also accounted for Justin Langer with his very first delivery when the opener - playing his 100th Test match - was struck on the side of the helmet and had to be helped from the field with concussion.
Langer is not expected to take his place in the batting line-up until Australia's second innings.
Ntini completed his 12th international five-wicket haul when Warne, who had been forced to the crease in only the 25th over, was caught by Shaun Pollock on the fine leg boundary after a stand of 68 with Hussey.
Adam Gilchrist was also guilty of over-attacking when he gifted a below-par Andre Nel his first wicket of the match.
Gilchrist fell into the trap set by stand-in captain Jacques Kallis when he pulled Nel straight into the waiting hands of Jacques Rudolph in the deep after being cramped for room.
But Warne and Lee produced valuable run-a-ball cameos to edge Australia close to taking a slim lead into the second innings despite the loss of Hussey (73) as the light started to fade.
Earlier, a rearguard action from spinner Nicky Boje helped South Africa pass 300 after resuming day two at 238-6.
Boje blitzed his way to 43 off 46 balls before falling to Kasprowicz 45 minutes before the lunch interval to signal the end of the innings.
Langer claimed his second catch of the morning after earlier combining with Lee to snap up overnight not out batsman Ashwell Prince for 93, his maiden Test 50.
Prince and Boje added 34 runs for the eighth-wicket as the Proteas started day two in more positive fashion than day one.
Lee (3-57) and Stuart Clark (3-81) finished with Australia's best bowling figures.