Microblogging Web site Twitter has bought Summarize, a search engine tool that indexes posts on social networks, MediaPost Publications reported Wednesday.

Twitter will employ five of the six Summarize engineers, as Jay Verdy, founder and CEO, leaves to work on another project.

The venture is "an important step forward in the evolution of Twitter as a service and as a company," Biz Stone, co-founder of Twitter, stated in a post on the company blog, MediaPost reported.

Summarize will become part of the Twitter brand name, as the search function will become one of the services that the firm provides, according to the Washington Post.

Summarize allows Twitter users to look for other users and themes, as well as to set up an RSS feed for the search or create a posting with the results. Summarize is not the only search engine that Twitter has; others include Tweeetscan and Twellow.com.

“... by acquiring Summize, Twitter is seemingly solidifying its position in the social media sphere and possibly foreshadows the development of a paid search advertising scheme operated via the search facility, potentially rivalling the likes of Facebook and MySpace for a piece of growing social advertising revenues,” a Big Mouth Media article stated.

The estimated cost of the acquisition is US$15 million in “mostly stock” and cash, according to MediaPost.