According to one article: 77-86° F (25-30° C). Another one that was a bit older, referenced an email from Dr. Tim Hovanec:
Bio Spira from Marine Labs contains Nitrosomonas, Nitrosospira and Nitrospira. While it is best if refrigerated until used, recent research has shown that it has a 6 month shelf life at room temperature (Dr. Tim Hovanec, electronic mail, 12/29/03). It can not be overdosed. Repeated dosing of your aquarium with ammonia removing liquids (such as BIO-Safe, Amquel, Ammo-lock and Aqua-Safe) can inhibit the beneficial action of BIO-Spira. Ammonia removing liquids should only be used to initially treat tap water. It is normal to have a small (<2 ppm) amount of ammonia or nitrate during the first few days after set-up. These concentrations are not harmful and will quickly drop to zero with proper use of BIO-Spira. (8) Optimal conditions for Bio Spira: Water Temperature: : 60°F-87°F (15°C-31°C) pH: range between 7.0-8.5 Within 24-48 hours, the bacteria will attach to the BIO-Wheel®, gravel, or other surface in the tank and your water should be clear. Don't use antibiotics. No UV light filters or proteain skimmers for 48 hours. (9, Dr. Tim Hovanec, electronic mail, 12/29/03)
So, it looks as though it grows just fine within a 27F degree range.