The City Council passed a bill last night outlawing discrimination based on "gender identity or expression," a measure aimed at protecting transsexuals who say they are denied jobs and housing, barred from trying on clothing in stores, and harassed by police officers who assume they are prostitutes.

Passed without debate, the bill makes Baltimore the nation's 53rd locality or state to explicitly prohibit discrimination against transsexuals, according to Lisa Mottet, a lawyer with the National Gay and Lesbian Task Force's Transgendered Civil Rights Project.

Boston, Philadelphia and New York City passed similar measures this year, she said.

The city had previously outlawed discrimination on the basis of race, color, religion, national origin, ancestry, sex, marital status, physical or mental disability and sexual orientation. Supporters said it was important to add gender identity or expression because transsexuals face immense discrimination.

Terri Johnson, 29, of Charles Village said she is tired of police assuming she is a prostitute because she is a transsexual and hopes the bill will help.

"Some girls just have to do what they have to do to earn a living, but the majority of us have regular jobs," said Johnson, a day care provider. "We don't want to be harassed."

Also last night, the council passed an ordinance intended to keep ammunition out of the hands of minors. The bill requires some sellers of ammunition to register with the city health commissioner and keep logs of all sales. The logs must be available for inspection by police.

The council also gave preliminary approval to a bill that would make it illegal to sell or transfer BB guns, air rifles or air guns to a minor. The council is scheduled to take a final vote on the measure next week.

The council had been expected to give final approval to legislation giving the city the authority to acquire up to 3,300 properties for an east-side revitalization effort centered around a biotechnology park north of the Johns Hopkins medical complex.

Action was delayed until next week because of technical amendments.