A group of workers at Whole Foods Market is trying to form a union, seeking better compensation and benefits and charging that conditions have worsened since Amazon bought the organic grocer last year.

In an e-mail recently sent to Whole Foods (WFM) employees, the union drive’s organizers said layoffs and consolidation at stores had put employees’ livelihoods at risk, and that more was likely to come. The group proposed demanding a $15-an-hour minimum wage, better retirement benefits, paid maternity leave and lower health insurance costs, among other benefits.

“The success of Amazon and WFM should not come at the cost of exploiting our dedication and threatening our economic stability,” the authors wrote.

It’s unclear how widely the letter was shared inside the company. The Wall Street Journal, which reported the e-mail and union drive, said the plan was to send it to employees at most of the 490 Whole Foods stores.

Executives at Whole Foods, one of the largest U.S. grocers without union representation, have long characterized their workplace policies as generous and said employees have a direct line to their managers, an assertion a company spokeswoman repeated in response to the organizing push.

“We’re not so much anti-union as beyond unions,” Whole Foods CEO John Mackey has said, citing the company’s high marks in rankings of the best corporate workplaces.

But the Austin, Texas, company’s sale to Amazon last year opened a door for organized labor, activists say. The $13.5 billion deal put a crunchy workplace culture — whose corporate values include worker happiness and community service — under the umbrella of Amazon, a demanding workplace known for customer obsession and expertise in the finer points of efficient, technology-driven capitalism.

Amazon has resisted previous attempts by its workers to organize. The company has grown into a bigger target for the labor movement as rapid expansion of Amazon’s warehouse network helped make the Seattle company the second largest U.S.-based private sector employer, behind Walmart, with about 575,000 employees.

The experience of Amazon employees has been a subject of public debate recently after Vermont Sen. Bernie Sanders criticized the company for its treatment of its warehouse workers, citing years of media reports that found a high-pressure workplace. Amazon, which last week called Sanders’ claims inaccurate in a rare public response to outside criticism, has taken to social media to stand up for its working conditions, assigning more than a dozen employees the task of discussing their personal experience in warehouses — in what have been uniformly positive tones.

Some Amazon employees are represented by unions in Europe, where workers in the last year have staged strikes to coincide with shopping season peaks like Amazon’s Prime Day promotion and Black Friday.

The Retail, Wholesale and Department Store Union (RWDSU), which has been in communication with Whole Foods and Amazon workers for several years, is aware of and assisting the Whole Foods drive, a spokeswoman for the AFL-CIO-affiliated union said. “Amazon is raising a generation of precarious workers and that is against everything our union stands for,” said Stuart Applebaum, RWDSU president.