The search alliance between Bing and Yahoo hasn’t seemed to affect Google’s dominance. In fact, the latest search ranking report from Hitwise reveals that Google gained ground in the search market during the four-week period ending October 2.

According to the data, Google accounted for 72.15 percent of searches in September 2010, demonstrating a 1 percent increase over August. Meanwhile, Bing-powered searches saw a net loss of 2 percent last month. Even though Bing.com fielded 10.10 percent of queries (more than a 2 percent increase over August), searches conducted on Yahoo sites declined by nearly 5 percent. This resulted in overall losses for Bing-powered results.

Hitwise also found that Google has maintained a strong lead in driving traffic to key industries. Google saw gains across all verticals, delivering a total of 22.38 percent of automotive traffic, 16.29 percent of health, 20.10 percent of shopping and 30.03 percent of travel.

Marketers should keep this in mind as they optimize their sites to catch organic traffic this holiday season. Additionally, Google’s dominance may encourage them to focus paid search campaigns on the search giant.

At the same time, Hitwise shows that Bing and Yahoo demonstrated impressive year-over-year gains in driving shopping traffic last month. Yahoo increased by 7 percent, accounting for 4.17 percent of shopping traffic, while Bing saw a 55 percent increase, directing 2.94 percent of traffic to shopping sites.

Brands that want to plan holiday search ad campaigns for either Yahoo or Bing sites should migrate their paid search accounts to the Microsoft adCenter now, if they haven’t already. As Brafton reported this morning, Yahoo has set an October 25 deadline for adCenter migration. Plus, the earlier campaigns are switched, the more likely marketers will see success in the transition to Bing-powered ads on both sites this season.