TwitterTwitter has hired a trio of firms as its first outside lobbyists to work the DC legislative and regulatory thicket.

The San Francisco-based micro-blogging operation has hired Mehlman Castagnetti Rosen & Thomas to deal with government surveillance and countering violent extremism, cybersecurity, privacy, immigration reform and open Internet, according to its federal filing.

Bruce Mehlman (former Commerce Dept. assistant secretary for tech policy), David Castagnetti (former staffer to Democratic politicos Sen. Max Baucus and Congressman Norm Mineta), Dean Rosen (ex-health policy counsel for Senate committee on labor and human resources) and David Thomas (ex-FTC Congressional director and VP Al Gore aide) head the 10-member team from their firm.

Twitter tapped Millennial Bridge's Lauren Culbertson (former deputy communications director for Republican Sen. Johnny Isakson) for Net Neutrality, patent reform and government surveillance issues.

The microblogger selected The Joseph Group's Kevin Joseph (former staffer on House and Senate commerce committee) for electronic communications privacy, patent reform and government surveillance.

Twitter spent $160K for lobbying during the first-half.