Is a nikon polyester bag safe to keep my camera from getting fungus?

I just bought a nikon d3200 bundle package and the bag that came with it is 100% polyester.

That bag was fine for shipping and probably kept out any moisture that the packaging may have picked up while it was being shipped to you.

However.

You never want to seal your camera or lenses in a plastic bag. It will only encourage fungus from growing in your equipment. If you live in an area where this is a problem, you need to build a "dry box" which will prevent moisture from aiding in the growth of fungus.

An air-tight transparent box is an excellent and inexpensive way to protect your lenses from fungus growth.

UV light destroys fungus, so letting your dry box sit where UV light is plentiful would be an excellent start. Adding Silica Gel packets to the inside of your dry box is also helpful

There's a more technologically advanced way to keep your gear dry and that is to buy a Digi Cabi Electronic Dry Cabinet AD-050. They cost about US$200

There are many tutorials the explain how to build your own dry box on Youtube.

Indeed any moisture may contain seeds of something, including fungus, so never a good idea to put a camera or similar item into a sealed bag for a long time.