The number of companies in the Twitter ecosystem keeps contracting. But not for a necessarily bad reason, but because they keep getting purchased. And what’s crazy is that it’s largely one person who has been buying them up: Bill Gross. We’ve just learned that his company, now called UberMedia, has just acquired TweetDeck.

We’re hearing that the deal, which happened recently, was in the $25 – $30 million range. And this is clearly the largest deal they’ve done yet as TweetDeck is the largest Twitter client outside of Twitter’s own properties.

This deal follows Gross’ company scooping up UberTwitter last month — a popular Twitter client for both BlackBerry and iPhone devices. And prior to that, earlier in January, they bought EchoFon, another popular Twitter client. But again, TweetDeck instantly becomes the crown jewel of the empire. And it means that UberMedia now owns a significant part of the overall ecosystem.

UberMedia has actually changed its name a few times now, partially due to these acquisitions. In April 2010, they launched as TweetUp, then they became PostUp, and then, following the UberTwitter deal, they became UberMedia. The company also own the popular Android Twitter client Twidroyd and Popurls (both of which they bought in July of last year), as well as the ad product, FollowMe. Overall, they fall under Gross’ Idealab.

The UK-based TweetDeck had raised a little over $5 million in funding.