Since its founding 23 years ago, Amazon.com Inc. has upended the business of selling books, music and just about everything else we consume — except food. 

Not anymore. In one fell swoop, Amazon founder Jeff Bezos has bought his way into the supermarket business with the $13.7 billion acquisition of Whole Foods.

The surprise deal shakes up the $800 billion grocery sector — and the broader retail industry itself — by marrying Amazon’s vast scale and digital prowess with Whole Foods Market Inc.’s 460 stores and fresh-food distribution network. 

The acquisition threatens traditional grocers such as Kroger Co., which were already reeling from food deflation and encroachment from new competitors like German discounter Lidl. Shares of rivals took a hit. The deal will likely spur other companies to defend themselves with their own buying sprees, consolidating the fragmented industry of feeding Americans.

“This is a game changer,” Zachary Fadem, an analyst at Wells Fargo & Co., said. “It’s a warning shot for the food retail industry that competition likely heightens on top of an already challenging backdrop.”

The deal comes after Seattle-based Amazon spent nearly a decade trying to find a way into the fresh-food delivery business through various endeavors, without much success. None other than John Mackey, Whole Foods chief executive officer, once predicted that Amazon’s quest for grocery deliveries would be “Amazon’s Waterloo.”

Now, Bezos will be Mackey’s boss, and the combination of those two pioneers could upend the staid supermarket business. Amazon’s various forays into selling groceries — Amazon Fresh, Amazon Pantry, Prime Now — will get a boost from Whole Foods and its affluent customer base.

‘Whole Paycheck’

Only about 1 to 2 percent of the industry has moved online. That is expected to change, according to Stifel Nicolaus & Co. analyst Marc Astrachan.

Amazon’s ownership will also likely result in lower prices at Whole Foods, whose expensive products earned it the nickname “Whole Paycheck.” That could force other supermarkets to follow or lose customers, Astrachan said.

“Amazon has been in the food business for over 10 years and to now come to the conclusion that it needs physical brick-and-mortar stores is a pretty big deal,” Jefferies analyst Dan Binder said in a note. “Amazon gains expertise in grocery and organics in particular.”

That development challenges big-box retailers Wal-Mart Stores Inc. — the nation’s biggest grocer — and Target Corp., whose food business has floundered of late. Shares of all major U.S. retailers, including drugstore chains like Walgreens Boots Alliance Inc. that also sell food, were all down more than 3 percent Friday.

Wal-Mart’s Plan

Wal-Mart has thus far parried Amazon’s advances by paying $3.3 billion for online marketplace Jet.com last year. Its curbside pickup of online grocery orders is now in more than 600 of its 4,700 U.S. stores. Overall, the company’s U.S. online sales rose 63 percent last quarter.

“They are on offense and that is a good position to be in,” Binder said, referring to Wal-Mart.

The acquisition could pose a bigger threat to Target, which has been building smaller stores in cities like New York to attract the affluent urban shoppers coveted by Whole Foods and Amazon, said Kurt Jetta, chief executive officer of TABS Analytics, a consumer products research firm.

More than 57 percent of Target’s regular customers use Amazon’s Prime membership program, according to consultancy Magid Associates, compared with 42 percent of all consumers.

“This could annihilate them,” Jetta said.

Wal-Mart, Target or others could respond with their own bids for Whole Foods, or for other food retailers such as Sprouts Farmers Market Inc., which is now “100 percent in play,” according to Gordon Haskett analyst Chuck Grom. 

Amazon’s takeout price of $42 a share undervalues Whole Foods’ prospects and powerful brand, according to Rupesh Parikh, an analyst for Oppenheimer & Co. Earlier this year, Oppenheimer valued Whole Foods in the mid $40-range in a possible buyout. After the deal was announced Friday, it raised its target price for Whole Foods to $45 from $40.

“There could be some money left on the table,” Parikh said in a note to clients.