LOS ANGELES (JTA) — A decade ago in Los Angeles, two new organizations opened their doors with a call to prayer — or they would have if they had any doors to open.

Ikar, led by Rabbi Sharon Brous, and Nashuva, led by Rabbi Naomi Levy, were conceived separately. But when they launched in 2004, both offered a novel, and in many ways similar, approach to Jewish spirituality and community — regularly scheduled, rabbi-led services that were not affiliated with any movement or institution, that met in rented space, and that were avowedly not synagogues.

“We were trying to walk into the conversation about Jewish identity and community and ritual without preconceived ideas about where we would land,” Brous told JTA, describing the beginnings of Ikar. “What we were trying to do didn’t follow any model that already existed.”

Since then, however, the format pioneered by Nashuva and Ikar has become its own recognizable model, and similar spiritual communities with a noticeably common style have sprung up in a number of other cities across the country.

Prayer is designed to be heartfelt and arouse the spirit. Often there is clapping, dancing and singing without words. Worshipers tend to skew young, informal and hip. The groups don’t own buildings; typically they meet in up-and-coming or already desirable neighborhoods.

The communities are led by charismatic rabbis who stress innovation and outreach to Jews who feel alienated from existing Jewish institutions. They are nondenominational. They often don’t know exactly how to describe themselves.

And most, but not all, have one more common element: They were founded, and are still being led by, female rabbis.

In 2006, Rabbi Rachel Nussbaum launched The Kavana Cooperative in Seattle. In 2011, Rabbi Noa Kushner opened The Kitchen in San Francisco and Rabbi Lizzi Heydemann initiated Mishkan Chicago in the Windy City. In 2012, Rabbi Lori Shapiro started Open Temple in the West Los Angeles neighborhood of Venice.

This new paradigm represented a sharp break with the past and has found a receptive audience among a younger cohort.

As noted by David Myers, the chair of the history department at the University of California Los Angeles, 20th-century American Judaism was defined in large part by building brick-and-mortar institutions. But the new rabbi-led communities are part of a 21st century spate of innovation outside the the established boundaries of Jewish institutional life.

“[Younger] people feel that it’s much more important to find their spiritual voice than to build up an institution for the institution’s sake,” Myers told JTA.

Thus, these communities founded by women are part of a much broader landscape.

A number of male rabbis also have formed and led innovative spiritual communities. Two are in New York: Rabbi Andy Bachmann founded Brooklyn Jews in 2003 and later folded it into the borough’s Temple Beth Elohim, and Rabbi David Ingber started Manhattan’s Romemu, a Jewish Renewal shul, in 2006.

Other models have proliferated, too.

Kehillat Hadar, founded in 2001, helped launch a movement of independent, lay-led minyanim that formed in cities throughout the country to pray without clergy or professional staff. The 6th & I Historic Synagogue in Washington, restored and relaunched in 2004, is now among several organizations housed in former synagogue buildings that host a combination of prayer services and community events.

Well-established synagogues also have experimented with prayer services featuring nontraditional music, looser structures and an emphasis on a warmer, more communal feel. In Denver, for example, Rabbi Bruce Dollin of the Hebrew Educational Alliance synagogue instituted a second service — with drumming and a “davening team” to help lead — that took a page from independent spiritual communities.

But rabbi-led spiritual communities, unaffiliated with a movement and untethered to a single home building, has become one part of the Jewish world where female rabbis have not only found a foothold but have taken the lead as pioneers and innovators.

It hasn’t been easy. The women who founded these communities have struggled to build organizational structures from scratch, to scrape together funds to rent space and pay salaries, and to connect with a target audience that often is disconnected from the normal channels of the Jewish communities.

Some have even had to bypass roadblocks set up by existing Jewish institutions and colleagues who have seen them as rivals.

“It’s a double-edged sword because on the one hand, the excitement of creating something from nothing is that you don’t have to deal with, ‘Well, we’ve always done it this way,’ ” Levy told JTA.  “The frightening part is not having any structure. When we started Nashuva, we had no money, we had no staff, we had no people. There was no community.”

Yet the enormous challenges also provide the opportunity for women to revolutionize spiritual and institutional life.

“Many women aspire to leadership, but they also aspire to change how leadership is offered,” said Shifra Bronznik, founding president of Advancing Women Professionals and the Jewish Community, a nonprofit dedicated to supporting female professionals in the Jewish world. “That’s actually easier to do if you’re building from the ground up.”

As noted by a number of the rabbis, as well as a number of Jewish communal professionals, traditional Jewish institutions — and the lead roles in them — have been shaped largely by men. Thus, the increasing prevalence of female rabbis opens up the space to rethink certain patterns.

“By definition, having a woman rabbi in your community means you’re not going to do things the way they’ve been done for the last 2,000 years,” Ikar’s Brous, 41, told JTA. “That creates a space for fluidity in organizational life.”

Some of those changes involve aspects of organizational life with a gendered component to them — for example, the role of a rabbi as the traditional male “breadwinner,” with a wife to take care of the family.

“There’s an old-school model where the rabbi is married to the congregation,” said Nussbaum, 38, of Kavana. “That’s the rabbi’s first priority, and the role is sort of boundless around that.”

In other ways, that sense of reimagining can also penetrate approaches to the religious texts as well.

“Women need to reinvent Judaism in order to see themselves reflected in the Jewish narrative,” said Bronznick, who has worked with several of these rabbis on issues related to women’s organizational leadership.

“They’re creating something that never was, which is a Jewish narrative authored in the voice of woman,” she said.

Strikingly, many of the innovative female rabbis come from the Conservative movement, the most recent of the denominations to ordain female rabbis, in 1985. Levy, Brous and Nussbaum all were ordained by Conservative Judaism’s flagship Jewish Theological Seminary, while Heydemann, 33, attended the movement’s Ziegler School of Rabbinic Studies at American Jewish University in Los Angeles.

Kushner, 44, ordained at the Hebrew Union College-Jewish Institute of Religion in New York, is a Reform rabbi like her father, Lawrence Kushner, who is also an author, while Shapiro, 43, was ordained at the nondenominational Academy for Jewish Religion in Los Angeles.

Not all of the female-led communities have broken the mold in the same way. Thus, for example, Ikar and Nashuva, the two early innovators in the field, have taken somewhat different paths.

Levy, 52, describes Nashuva as “a spiritual outreach community” aimed squarely at Jews who feel disconnected from Jewish life. Nashuva operates on a shoestring budget, with a payroll consisting only of Levy and the members of its eight-piece band, and most of the year meets just twice a month — for Friday-night services at the Brentwood Presbyterian Church and on a Sunday for a community service event.

This is precisely as Levy wants it — she says she has no desire to open a religious school, expand her staff or institute any kind of membership model. Instead, Nashuva raises money only through voluntary contributions, including a suggested donation of $350 for the High Holidays.

Although Nashuva remains nondenominational, Levy has retained close ties to the Conservative movement. A member of the first class of women admitted to the Jewish Theological Seminary’s rabbinic program, she served on the executive council of the movement’s Rabbinical Assembly, and she travels regularly to speak at synagogues about how they incorporate some of Nashuva’s innovations into congregational life.

Ikar, by contrast, has expanded rapidly. Brous is now one of two full-time congregational rabbis, along with a permanent staff of 14, plus seasonal and teaching staff, and Ikar operates a preschool and religious school. It offers tiered membership plans and charges non-members for High Holidays tickets. (This reporter has been a member of Ikar since 2009.)

In certain ways, Ikar also has served as the mother ship of the rabbi-led spiritual community movement and helped create a mentoring network among several of the congregations.

When Nussbaum left her suburban Seattle congregation to start Kavanah, she sought out Brous for advice. And when Kushner decided to start The Kitchen, she spoke to Nussbaum and Brous. Heydemann, in turn, served as a rabbinic fellow under Brous at Ikar, and already had known Kushner at Stanford University while she was an undergraduate and Kushner was the Hillel rabbi.

Each of these communities, in turn, has developed its own distinctive shape and culture.

Kavana is based on a cooperative model in which members are expected to take an active volunteer role in helping to put together and run events, and are encouraged to attend at least one community event per month.

The Kitchen has embraced an experimental, start-up ethos. The founders partnered with a design firm, IDEO, to help think through not only a design aesthetic for the community’s materials (modern typefaces, no Judaica motifs), but also the service itself from the ground up. As befits its name (chosen to suggest an open, familiar place to experiment and try things out), The Kitchen has also made a point of partnering with trendy local restaurants for Shabbat meals.

Mishkan Chicago has established itself as a younger-skewing congregation particularly focused on singing and prayer.

Several of the communities are moving toward affiliating with one another in a more formal way.

In May, Brous, Kushner, Nussbaum and Heydemann — along with Romemu’s Ingber, Amichai Lau-Levie of Lab/Shul in Manhattan and Rabbi Scott Perlo (a former rabbinic intern at Ikar) from Sixth & I Historic Synagogue — met at the Leichtag Ranch north of San Diego to discuss ways to work together more closely and potentially articulate a common vision. The group’s participants, who jokingly call themselves the G7, said the discussions had not yet turned into anything concrete, but suggested that something more definite would be forthcoming in the coming weeks and months.

They all stressed that they were not looking to form any sort of movement.

The innovative communities and their rabbis are increasingly being cited as models for the Jewish future. Several were honored in the Slingshot Fund’s newly issued directory of innovative Jewish organizations, and Levy says she travels on a monthly basis to speak to synagogues about spiritual outreach and creativity.

How precisely these communities will evolve remains an open question. And in certain ways, they already have — adding new services as the congregations grow and as members’ needs and desires change. Kavana has created a Hebrew immersion preschool and religious school, and has added adult education programs as its cohort of older congregants grows. The Kitchen’s “Shabbatify” program organizes Shabbat dinners of 12 to 20 people in participants’ homes, and the community is in the process of opening a store to sell its self-designed prayer books and a Passover game.

But Myers, an Ikar member from its early days, says that as the communities grow and evolve, those that wish to survive in the long term will inevitably need to develop their institutional forms and find new ways to generate and harness energy.

“Ironically, the way to marshal and galvanize that new energy is probably to get a building,” he said.

Indeed, Ikar for the past several years has been looking into buying or constructing its own building. That would represent a profound symbolic move from its early days.

“Ikar,” Myers says, “was the anti-building form of spiritual community.”

But ultimately, the rabbis argue, the measure of their success or failure has nothing to do with buildings, denominations or labels. Rather, staying true to their mission involves not differentiating themselves but staying relevant.

“I don’t think I’m re-creating Jewish world,” Kushner told JTA. “I’m doing my part for my generation. These ideas of trying to bring immediacy, relevancy, meaning — these are not brand new ideas. They’re ideas that every good rabbi struggles with.”