Only a week after Yahoo and Microsoft announced they had begun transitioning Yahoo's searches to Microsoft's Bing search infrastructure, the companies have now confirmed that the integration of the back-end technology is complete.

"Today I am happy to share that Bing is powering Yahoo's search results in the U.S. and Canada," Satya Nadella, senior vice president of Microsoft's (NASDAQ: MSFT) Online Services Division, said in a post on the Bing Community Blog Tuesday. Yahoo also took a moment on Wednesday to address speculation and criticism that the deal signified its exit from the search market, reminding consumers -- and search marketers -- that it is still very much in the game.

Shashi Seth, Yahoo's senior vice president of search products, likened the company's decision to cede the engineering component of its search engine to Microsoft to the common practice of selective outsourcing in other industries. Boeing and Airbus contract with companies like Royals Royce, United Technolgies and GE to build their engines, Seth noted in a blog post. "But, does that mean that Boeing and Airbus are no longer airline manufacturers?" he asked rhetorically.

"People who assume that search is only about indexing, crawling and relevance of Web documents are mistaken," Seth said.

For search marketers, he took pains to argue that Yahoo is still very much a relevant and essential buy.

"Yahoo search supplements Microsoft's Web index with Yahoo's own content, content from third party relationships and content from social networks like Twitter," Seth said. "We still maintain the technology, science, scale and infrastructure required to crawl, index and rank this data -- and all in real-time."

While Yahoo promises to keep improving and innovating in the consumer-facing layer of the search engine, Microsoft is temporarily increasing the rate at which its adCenter ad index crawler (called "adidxbot") crawls advertisers' sites to between 20 and 30 queries per second (qps).

"Along with our consistent efforts to increase relevance for your adCenter campaigns, we will be temporarily increasing the rate at which your sites will be crawled to 20 to 30qps. This is within the accepted standards for crawl rates, and is vital to continuing to provide the most relevant advertising experience possible," media specialist Tina Kelleher said in a post on the adCenter Blog this week.

Kelleher went on to point out that the adCenter ad index crawler does not crawl Bing indexes -- that is done by the Bing index crawler (called "msnbot"), she said.

After an acrimonious courtship that led to Microsoft withdrawing a bid to buy Yahoo (NASDAQ: YHOO) outright, in July 2009, the two companies came to a 10-year agreement whereby Microsoft will provide the underlying search and advertising technologies that support Yahoo's sites in return for a share of the revenues that searches on those sites yield.

The two companies also announced last week that they are testing the transition of advertising accounts to Microsoft's adCenter, and tentatively plan to begin transitioning Yahoo Search Marketing customers to Microsoft's system in time for the holiday shopping season.

Meanwhile, how do you tell whether a Yahoo page is now being served searches from Microsoft?

At the bottom of the page, the screen will read "Powered by Bing."

Stuart J. Johnston is a contributing writer at InternetNews.com, the news service of Internet.com, the network for technology professionals. Follow him on Twitter @stuartj1000.