Seattle ? That soap scum that forms on the shower curtain? It’s really a biofilm loaded with more than a billion bacteria per cubic inch.

The moving belt on an escalator? When you put your hand there, you’re dipping into a puddle of bacteria left by all those who went before.

How about the potting soil for your petunias? It’s the happy home of a pathogen called Microbial Avian Complex, a potentially troublesome bug.

Then there’s the sponge you use to rinse dishes at the sink. Yep, loaded with thriving bacteria.

If this makes you want to go relax in a hot tub, think again. The air wafting from the hot water is probably loaded with microbes, some of them able to give you a hacking cough.

It’s a microbial world, said Norman Pace, a researcher at the University of Colorado at Boulder. Virtually everything you touch is coated with the little critters. You couldn’t escape them if you wanted to because your skin is covered with about 100 million bacteria, he said.

Yet, science knows very little about environmental microbes, how they live, reproduce and thrive in the natural world.

“We live in a microbial world, and I find it appalling that this is ignored by science,” Pace said Saturday at the national meeting of the American Association for the Advancement of Science.

Pace discovered the colonies of soap scum bacteria when, out of curiosity, he took a sample from his own shower curtain and examined it under a microscope.

“I was amazed,” he said. Later studies of shower curtains from other homes found the same thing.

Most of the soap scum bacteria is harmless to the healthy. But for people with compromised immune systems, such as patients with AIDS or on chemotherapy or with open wounds, some of the germs can be deadly.

Hands off

When he rides an escalator, Pace says he puts down only his knuckles because of the potential broth of bacteria that may be present.

The kitchen sink sponge, he said, “is a spectacular source of bacteria.”

Too hot to handle

Pace explored the microbial world of hot tubs after he was asked to investigate why some on the staff at a therapeutic swimming pool were developing “lifeguard lung,” a nagging cough that plagues pool workers.

He found that the air above a heated, indoor pool or above a hot tub is enriched with microbe by about 60 percent. Persistent exposure to the air caused the “lifeguard lung” in sensitive people. The same thing can happen around a hot tub.

“These findings are a bit scary. The bottom line is people should be aware of the risk of swimming in indoor pools or sitting in indoor hot tubs,” Pace said.