Amazon.com keeps piling up the acquisitions with growing companies in promising niches.

This time Amazon is acquiring LoveFilm International Ltd., a London-based video rental and streaming company with 2009 sales of about $158.8 million. Terms for the deal weren’t disclosed, but Amazon has held a 40% ownership share in LoveFilm since 2008. “LoveFilm and Amazon have enjoyed a strong working relationship since they acquired Amazon Europe’s DVD rental business, and we look forward to a productive and innovative future,” says Amazon vice president of European retail Greg Greeley.

Amazon, No. 1 in the Internet Retailer Top 500 Guide, is acquiring LoveFilm to help grow its entertainment content base in Europe, the web retailer says.

LoveFilm was formed in 2004 and today offers its 1.6 million subscribers in the U.K., Germany, Sweden, Demark and Norway access to a library of 70,000 titles on DVDs, Blu-ray disks and streamed directly to personal computers, TVs and other electronic devices. “We look forward to a productive and innovative future,” says LoveFilm CEO Simon Calver.

The deal is expected to close by March 30, says Amazon.

The acquisition of LoveFilm is Amazon’s third in recent months. In October, Amazon acquired BuyVip.com, a fashion and lifestyle online buying community with more than 6 million members in Spain, Germany and Italy. In November, Amazon also acquired Quidsi Inc., the parent company of Diapers.com and two other e-commerce sites focused on mothers and families, in a deal valued at $500 million.