JOIN USBiedermann shock for Phelps
Biedermann, who had broken the world record to take gold in Sunday's 400 freestyle, swam one minute 42 seconds to beat Phelps' Beijing Olympic mark of 1:42.96.
"For the moment it is just like a dream. It's such an amazing feeling. I'm so fine," he told reporters.
Asked if he had thought he could beat Olympic champion Phelps, who won the world title in 2005 and 2007, Biedermann said: "Maybe in two or three years, not now."
Second-placed Phelps, who finished in 1:43.22, said: "Theoretically that was a pretty good swim for me. Three tenths off my best time after taking sixth months off. I'm not happy but I know I didn't train much this year."
Russia's Danila Izotov took bronze.
In women’s section, Italian Alessia Filippi beat off a sustained challenge from Dane Lotte Friis to win the 1,500 metres freestyle title in front of an ecstatic home crowd. Filippi swam a championship record of 15 minutes 44.93.
"It is too little to say I am amazed. I wanted this medal, I wasn't sure of getting it because my opponents are strong," Filippi told reporters.
Friis was quickest in the heats and led early on but Filippi wore her down before being roared on to victory at the Foro Italico's open air pool. Camelia Alina Potec of Romania was a distant third.
The men’s 100 metres backstroke title went to Japan's Junya Koga, who beat the championship record he set in the semifinals to prevail with a time of 52.26 seconds. Germany's Helge Meeuw took silver and Spain's Aschwin Wildeboer claimed the bronze medal.
World and Olympic champion Aaron Peirsol failed to make it past the semifinals on Monday. The American backstroke ace can take consolation from the fact that the world record of 51.94 he set earlier this month still stands.
Rebecca Soni snatched gold in the women's 100 metres breaststroke. The American, who broke the world record in Monday's semifinal, finished in one minute 04.93 with Russia's Yuliya Efimova second and Kasey Carlson of the United States taking bronze.
Tuesday saw another set of world records re-written as Federica Pellegrini broke her own world mark in the women's 200 metres freestyle semifinals. The Italian, who had smashed her own world record to win Sunday's 400 final, surged through the water in one minute 53.67 to better her March effort of 1:54.47.
Cameron van der Burgh too destroyed the 50 metres breaststroke men's world record in the semi-finals with the South African clocking 26.74 seconds to beat Felipe Franca da Silva's mark of 26.89.
Hi-tech suits banned
The hi-tech swimsuits that have led to a deluge of world records will be banned from January when the sport will revert to costumes made from textiles, swimming's governing body FINA said on Tuesday.
"The material can only be textile fabric," FINA executive director Cornel Marculescu told a news conference. "The shape (of the costume). For men it shall not extend above the naval or below the knee. For women it shall not extend above the neck, beyond the shoulders or below the knee."
FINA said a scientific committee would be appointed to define textile fabric for its regulations by the end of September after its executive discussed how to implement the decision made at a congress last week to dump the latest suits. Controversy over all-polyurethane suits has overshadowed the world championships in Rome, where the rapid rate at which records are falling has heightened fears for the sport's credibility.
Results:
Men: 200M freestyle: Paul Biedermann (Ger) 1:42.00 (WR), 1; Michael Phelps (US) 1:43.22, 2; Danila Izotov (Rus) 1:43.90, 3.
100M backstroke: Junya Koga (Jap) 52.26, 1; Helge Meeuw (Ger) 52.54, 2; Aschwin Wildeboer (Esp) 52.64, 3.
Women: 100M backstroke: Gemma Spofforth (Bri) 58.12 secs (WR), 1; Anastasia Zueva (Rus) 58.18, 2; Emily Seebohm (Aus) 58.88, 3.
100M breaststroke: Rebecca Soni (US) 1:04.93, 1; Yuliya Efimova (Rus) 1:05.41, 2; Kasey Carlson (US) 1:05.75, 3.
1500M freestyle: Alessia Filippi (Ita) 15:44.93 secs, 1; Lotte Friis (Den) 15:46.30, 2; Camelia Potec (Rom) 15:55.63, 3.