Defending champion Angelique Kerber survived an onslaught from fellow German Carina Witthoeft to advance to the Australian Open third round.
Kerber – top seed at a Grand Slam for the first time – struggled with her serve in a second-set tie-break before prevailing 6-2 6-7 (3-7) 6-2.
The top seed, who was 29 on Wednesday, faces Czech Kristyna Pliskova next.
Venus Williams beat Swiss qualifier Stefanie Voegele 6-3 6-2 to reach the third round for the 13th time.
Williams, who played at her first Australian Open in 1998, is the oldest woman in the singles draw at 36 and is competing in her 73rd Grand Slam.
“I have to talk about my age every interview!” the American said. “I’ve played some of the greats.
“It’s an honour and privilege to start that young, and play this old.”
She later pulled out of the doubles competition with her sister Serena as a precaution to rest a sore elbow.
The 17th seed has never won the title in Melbourne, her best result finishing as runner-up to Serena in 2003.
She will next play Duan Yingying after the Chinese player beat Varvara Lepchenko 6-1 3-6 10-8.