London (AP) — A month after winning her 14th Grand Slam title, Serena Williams clinched her first Olympic gold medal in singles on the same Centre Court at Wimbledon. On the other side of London, Usain Bolt made a stuttering debut.

Williams fired an ace on match point Saturday to complete an easy 6-0, 6-1 win over Maria Sharapova.

The American now has a singles gold to add to the two Olympic doubles golds she won in 2000 and 2008 with her sister Venus. And she could still win doubles gold at the London Games — the Williams sisters play a semifinal later Saturday.

Williams, who lost only 17 games in her six Olympic matches, won her fifth Wimbledon in early July.

The Olympic Stadium was again crammed to its 80,000 capacity Saturday to watch Usain Bolt and the "Blade Runner" — Oscar Pistorius — make their first appearances.

Pistorius was cheered around the Olympic track, finishing second in his 400-meter heat to advance to the next round on his carbon fiber blades. The South African double amputee circled the oval with fans cheering him on in 45.44 seconds — good enough for second place in his heat and a berth in the semifinals Sunday night.

The 25-year-old South African was born without fibulas and his legs were amputated below the knee before he was a year old.

"I've worked for six years ... to get my chance," said Pistorius. "I found myself smiling in the starting block."

Bolt overcame a slow start to advance to the 100-meter semifinals.

"I stumbled on the start," the 25-year-old Jamaican said. "I really didn't do a lot of executing."

Bolt dominated the Beijing Games four years ago, winning golds in world-record times in the 100, 200 and 4x100 relay — something no man had ever done at an Olympics. At the 2009 world championships, he lowered his 100 mark to 9.58, which still stands.

British rowers were the stars at Eton Dorney west of London, doubling their gold-medal haul on the final day of the Olympic regatta with victories by the men's four and the lightweight women's double sculls.

That left the host nation at the top of the rowing medals table with nine medals — four golds, two silvers and three bronzes — to surpass the country's record total of eight from the 1908 Olympics, which was also held in London.

Nicola Spirig of Switzerland outsprinted Sweden's Lisa Norden in the final meters to win the women's triathlon in a photo finish. Spirig crossed the line after the 10-kilometer run leg just a fraction ahead of Norden and in the same official time, with Erin Densham of Australia taking the bronze.

American Jamie Lynn Gray won the women's 50-meter three-position qualifying, setting two Olympic records along the way,and Jessica Rossi of Italy won the women's trap.

Canada picked up its first gold of the games when Rosannagh MacLennan won the women's trampolining competition. The 23-year-old MacLennan posted a score of 57.305, good enough to edge silver medalist Huang Shanshan and more than a point ahead of Wenna, who are both from China.

Lithuania gave the U.S. men's basketball team a scare, leading late in the game before the Americans rallied for a 99-94 win. LeBron James scored nine of his 20 points in the final four minutes for the U.S.

Carmelo Anthony added 20 points for the Americans and Linas Kleiza scored 25 to lead Lithuania, which led 84-82 with just under six minutes to play.

Li Xuerui left no doubt who was the best women's badminton player in the world when she beat world champion Wang Yihan in the all-Chinese final.

In track cycling, the British women's pursuit team shattered its own world record Saturday while qualifying for the gold medal race against the United States.

The team of Dani King, Laura Trott and Joanna Rowsell covered the 3,000 meters in 3 minutes, 14.682 seconds, lowering the mark of 3:15.669 that they set the previous day in qualifying.

It was the ninth world record broken on the pine wood surface of the London Velodrome. Seven of those records have been set by the British team, which won three of the four gold medals awarded on the first two days of the track cycling program.

In doping news, a Russian cyclist and Colombian runner were sanctioned by the IOC for failing pre-competition drug tests, bringing to four the number of official violations so far at the games.

The International Olympic Committee said Russian track cyclist Victoria Baranova was expelled after testing positive for testosterone on July 24 in Ratomka, Belarus. Her positive test was confirmed on Friday by cycling's world governing body.

Colombian 400-meter runner Diego Palomeque was provisionally suspended after testing positive for testosterone on July 26 in London. The 18-year-old athlete did not start in his scheduled heat Saturday.

Former 100-meter world champion Kim Collins was sent home from the Olympics for disciplinary reasons on Saturday. The St. Kitts and Nevis team said it "regrettably announced" that Collins, who it described as a "national hero," was leaving the Olympics.

Collins was kept out of his scheduled start in the 100 heats on Saturday. He was also entered in the 200 and 4x100 relay.

Later in the day at the Aquatics Centre, Michael Phelps will swim his last competitive race.

Phelps is heavily favored to add one more gold to his collection of 21 Olympic medals, 17 of them gold, when he swims the butterfly leg of the 4x100 medley relay, a race the Americans have never lost.

The 27-year-old swam his first Olympics in Sydney 12 years ago and is retiring after London.