The first step of Yahoo's transition from an in-house search infrastructure to Microsoft's Bing platform is complete. Yahoo announced the completed conversion today: its Web, image, and video search experiences on both desktop and mobile devices are now being served up by Bing. Microsoft meanwhile noted that the conversion currently only affects Yahoo's English search results in the US and Canada, with other languages to follow "in the weeks and months ahead."

The change comes over a year after Microsoft and Yahoo agreed to partner on search and ads in order to combat Google. The Yahoo search results still have the same appearance, except for the 7.5 point text stating "Powered by Bing™" at the bottom of the page.

We contacted both Microsoft and Yahoo to find out which countries will get the Bing-powered-Yahoo next but neither company was eager to share. "At this time, Yahoo! has not given details on international rollout, but I will keep you posted," a Yahoo spokesperson told Ars. Microsoft was only a bit more helpful. "As soon as we are up and running in North America, we will begin the work of scaling out internationally," a Microsoft spokesperson told Ars.

As we noted on Bing's one year anniversary, Microsoft's offering has been gaining credibility where its predecessors failed. Depending on which market share numbers you follow, Bing should now have somewhere between 16 and 28 percent market share in the US thanks to Yahoo's help. The hope is that with the additional hits, Bing will over time learn to provide more accurate results as the number two search engine behind Google.

In addition to the search results in the center of the page, the two companies are also working on the sponsored results in the sidebars. The move of Yahoo's search ad infrastructure to Microsoft's AdCenter platform is due for completion "later this fall," but both companies have said they are willing to postpone the move till early next year as it may disrupt the holiday season. The revenue model for the Yahoo Search BOSS program still needs to be finalized, and many search-related tools for publishers will be released "in the months to come."