Help with identifying mold

For the last few months I've had something growing in my pool's shower room that I haven't been able to identify or kill. I removed it about two weeks ago with high pressure water, then gave the area a good soaking with Clorox, and it is back again. Seems to grow from "not there" to what you see in the picture below overnight, or at least in no more than two days.

I built the room about four years ago and it is 6" (pine) wall studs with a pressure treated bottom plate, 5/8" OSB on the exterior and interior walls both wrapped with Tyvex, brick on the outside wall and vinyl siding on the inside wall as shown in the photo below. After installing the vinyl siding, I used clear silicon to seal the bottom, top, and other breaks in the vinyl siding. I leave the room's door open in the summer and the room gets plenty of ventilation, but it still can be a damp location.

What you are looking at is where the wall meets the concrete floor, and a ruler (displaying inches) in the foreground. This appears as 1/2" oval or round nodules with the consistency and color of soft chocolate inside (the outer shell is a darker brown and is a bit harder), and it really clings to the cement and vinyl siding well. Any help with identifying this and tips on killing it would be most appreciated.