As MediaNews chief executive Dean Singleton negotiates to buy the Mercury News and other Knight Ridder properties in Northern California, he is reducing the size of his Denver Post newsroom. The Post is offering early retirement packages and buyouts to 25 full-timers, about 10 percent of the paper’s news staff, according to the Denver Business Journal. Newspaper Guild leaders in San Jose, who have organized the “savethemerc.com” web site, have expressed concerns that Singleton will make deep cuts in news if he acquires the Merc, Contra Costa Times, Palo Alto Daily News and Monterey Herald. Meanwhile in Denver, while the Post is cutting, the rival Rocky Mountain News won two Pulitzer Prizes on Monday and an official there says the paper is in a “hiring mode.”