Bacteria blend - safe or dangerous?

Hi,
Does anyone know if any of the following bacteria are known for high diacetyl production, or other bad beer flavors for that matter:
Streptococcus thermophilus
Lactobacillus delbrueckii subsp. bulgaricus
Lactobacillus acidophilus
Bifidobacterium lactis
I want to brew a slightly sour Wit, but didn't plan ahead very well and all I have is a yogurt starter that contains a blend of those. Any insight into functionality here?
Thanks!

I've successfully made a berliner weisse with a yogurt culture. If you want a sharp lactic sourness, this technique works well. It finished at 3.3 pH.

However, you appear to want a mild sourness (~4.0 pH). In that case, I'd recommend a White Labs or Wyeast lacto strain (produces less lactic acid).

Great,
Thanks a lot. Sounds like it'd work out well for this!