Degradation of agar by a gram-negative bacterium.

An agar-degrading bacterium, having a guanine-cytosine content of 50-5 mol% has been isolated from sewage. This Gram-negative rod grew well in a simple salts medium containing various carbohydrates. Growing bacteria dissolved gels and suspensions of agar and agarose rapidly, but did not attack cross-linked agars. Agarase was cell-bound in exponentially growing cultures but was released into the medium at stationary phase. Both cell extracts and culture filtrates released reducing sugars from agar solutions and prevented them from gelling. Gels were not dissolved by enzyme solutions, but the turbidity and iodine-binding properties of the agar were decreased.