When their car broke down, parishioners provided rides because their work was so important.

At the church, where mass is performed daily, Father John said the sisters also take care of the sacristy (room for church furnishings, sacred vessels and parish records) and “God knows what else.”

“To us, those nuns are angels,” said Sissy McDonald, a lifelong parishioner of St. Mary’s, after a recent 7:30 a.m. mass.

The Sisters of the Holy Spirit in Tanzania was founded in 1964 by a German priest, Father Bernhard Bendel, as part of Opus Spiritus Sancti, a family of religious and lay communities he started in Germany to bring people together after the devastation of World War II.

In 1964, Tanzania also won its independence from Great Britain without bloodshed, and peace has endured since.

The Sisters of the Holy Spirit, who now number around 300 worldwide, also have a community in India. In the United States, they also serve in Oregon, Iowa and Pennsylvania.

Sisters Mary, Marietha and Euphemia are from Kilimanjaro’s Chagga tribe, which is about 75 percent Catholic. Their families are large, but they see them only once every three years. Sister Mary says she had considered getting married, but God’s pull was stronger.

St. Mary’s has had a long tradition of nuns serving the church. The Sisters of the Holy Names ministered there for 115 years, starting in 1868. They turned their convent into a hospital for the wounded of the Battleship Maine, which exploded in Havana Harbor before the start of the American/Spanish War.

But there had been a void for several years, when Father John asked whether the Sisters of the Holy Spirit, whom he knew of through a priest friend, might be interested in serving in Key West.

It worked out. The sisters love their life in the island city. The church provides them each with their own room in the homey but aging convent.

But there have been many adjustments. Sister Mary was especially frightened by the geography. “We come from the mountains, and everywhere here is water,” she said.

When Father John strolled with them down the main tourist drag of Duval Street, Sister Euphemia said it was a “miserable, bad place.”

All the Sisters were surprised by the “half-naked” people walking around and wondered why the tall women were so dressed up on a Sunday afternoon. Father John educated them about the town’s drag queens and transvestites.

“What in the world is going on, men dressed like women?” Sister Mary asked. “But we pray for them, too.”

Homelessness also was a new concept. Back home, despite the poverty, everyone has a roof over their head, albeit one made of grass. In Tanzania, everybody receives land that belongs to them forever. “Nobody can say at the end of the month, pay your bills or leave,” Sister Mary said.

And when St. Mary’s and its school faced dire economic times in 2009 and 2010, the Sisters insisted that they take a 50 percent cut in their already meager stipend provided by the Archdiocese.

To be “one of the people,” the sisters don’t wear their pristine, white habits outside the church. But their “everyday” attire gives them away: pleated skirts, pressed shirts, a scarf and a big silver broach inscribed in Latin with their religious community’s motto: “So that God may be all in all.”

Father John laughed about the time he walked with the sisters down tree-lined Whitehead Street and a drunk woman mistook him for her cheating ex-boyfriend.

“She’s yelling obscenities at me and saying now I have three black women to replace her,” he said. “When they turned around, she said: ‘Whoa, they are church women. Now you have to have church women to protect you, you little weasel.’ ”

Sometimes they will go to Mallory Square to see the sunset and “pray for the people.” Sister Mary said drunk people often will apologize to them.

“Their pure goodness evokes a response that calls us all to be better,” Father John said. “I know they make me want to be better.”