By Alexei Oreskovic

SAN FRANCISCO (Reuters) - Google Inc paid $151 million in cash to acquire popular restaurant review guide Zagat in September, the Internet company said in a regulatory filing on Wednesday.

The acquisition, which added a valuable brand to Google's content offerings and bolstered its push into the local commerce market, was one of 57 deals completed by the Web search company in the first nine months of 2011.

Google, the world's No.1 Internet search engine, has been acquiring companies at a rapid clip, as it moves to expand into new markets and adapt its product to a world in which consumers increasingly rely on mobile devices and social networking services to access the Internet.

Google also acquired Daily Deals, a privately held, German online coupon company, for $114 million in cash in September, Google said in the filing with the U.S. Securities and Exchange Commission. And it completed the acquisition of ITA Software for $676 million in cash in April.

Google said it completed 54 other acquisitions and purchases of intangible assets during the first nine months of 2011 for roughly $502 million.

During that same period in 2010, Google completed 37 deals for $626 million, excluding the acquisitions of Slide, AdMob and On2 Technologies, for which Google paid a combined $983 million.

Google announced its acquisition of Zagat Survey, which polls consumers and compiles reviews about restaurants, hotels and other businesses around the world, in September, but did not disclose a price at the time.

Google's largest deal to date, the planned $12.5 billion acquisition of mobile phone maker Motorola Mobility Holdings Inc is pending regulatory approval. Google has said it expects the deal, announced in August, to close later this year or early in 2012.

(Reporting by Alexei Oreskovic; editing by Andre Grenon)