TweetDeck is happy in joining the flock of Twitter users.

Completing the deal on Tuesday, Twitter announced Wednesday of its acquisition of TweetDeck, a London-based startup company with 15 employees, whose popular application allows users to read, write, and organize Twitter messages.

Published reports have pegged the acquisition at $40 to $50 million, but Twitter has not disclosed the terms of the deal.

TweetDeck, founded in 2008, was initially aimed towards Twitter, and later expanded its user-friendly browser to Facebook, MySpace and Linkedin platforms. TweetDeck is said to be the most popular Twitter application with a dominant market share.

TweetDeck founder and CEO Lain Dodsworth said in a TweetDeck blog post, the past three years have been an epic journey, with many highs and lows, accompanied by the constant thrill of never really knowing what to expect next. TweetDeck has developed from one team member and a single user, to a team of 15 members and a user-base of millions. Their focus on providing quality service for the Twitter-centric power-user contributed to the growth, the blog post stated.

Through this partnership with the official platform of Twitter, TweetDeck is expected to fill the need for brands, influences, and for creating an active platform for power users.

Twitter acknowledged power users, including companies, marketers and Twitter celebrities, as an important constituency worth investing in.