Theoil and gas price collapse has gotten the better of another oil and gasexploration company, with UltraPetroleum Corp. filing for Chapter 11 bankruptcy protection.

Ultra'sgreatest asset holdings are natural gas fields in , but it also holds acreage inUtah and Pennsylvania.

Inits bankruptcy filing, the Houston-based Ultra said it has assets of $1.28billion and debts of $3.92 billion. Ultra listed Disciplined Growth InvestorsInc. and Invesco Ltd. as its two largest equity securities holders, at 9.1% and7.9%, respectively.

Inan SEC filing May 3, Ultra said that the bankruptcy filing had accelerated itsobligations on several items, including its 5.75% senior notes due December2018 and its 6.125% senior notes due 2024. It also said it has received noticefrom the New York Stock Exchange that trading of the company's stock wassuspended after the close of business May 2, citing the bankruptcy filing.Ultra's shares are now being traded on the pink sheets.