Google on Thursday plugged a key gap in its growing portfolio of communication services with the acquisition of Gizmo5, a Californian start-up that handles internet-based voice calls and instant messaging.

Alongside its Google Voice, Google Talk and Gmail services, Gizmo5 will give the search company with a broad set of technologies for completing and managing voice, text and video communications. The acquisition was first reported earlier this week by TechCrunch, which put the purchase price at about $30m.

In a blog post, Google said the Gizmo5 engineers would join its Voice team, but did not outline how the services would be combined. The Voice service is based on Google’s acquisition two years ago of GrandCentral, another internet communications start-up.

Google’s growing ambition in internet-based communications has been apparent since the launch of Gmail in 2004, and, a year later, Talk, which enables computer-to-computer messaging and voice calls. The company later added features to Gmail to allow voice and video chat between users.

Users of Google Voice, meanwhile, are given a single number for all their phones, and can route calls between devices. Although it can be used to set up calls between traditional landline telephones it does not connect to internet-based networks such as Google Talk or Skype.

With Gizmo5 Google is set to overcome that technological limitation. That could also potentially open up a deeper integration of Voice with other online applications, including Wave, the ground-breaking collaboration tool that is meant to make it easier for groups of people to work together online.