Comparative biochemistry of alpha-glucan-utilization in Pseudomonas amyloderamosa and Pseudomonas saccharophila: physiological significance of variations in the pathway.

Growth patterns on and utilization of various alpha-glucans were investigated in Pseudomonas amyloderamosa and P. saccharophila. Maltose, maltodextrins (average chain length 7 glycosyl units) and glycogen supported excellent growth of both organisms and were extensively metabolized, although glycogen utilization in P. saccharophila was preceded by a prolonged lag phase. P. amyloderamosa produced limited growth on amylopectin and the carbohydrate was only partly degraded. It seemed likely that many of the unit chains liberated from amylopectin had a length exceeding the substrate range accepted by the maltodextrin permease (transport) system. A correlation was established between the pH of the medium and the utilization of glycogen and amylopectin for growth in P. amyloderamosa. The carbohydrates were at least partly utilizable at pH 6.0, whereas they could not support any growth at pH 6.5. Most likely, the lack of growth at the higher pH reflected the low activity of isolamylase at this pH. The enzyme patterns of maltodextrin catabolism in the two bacteria were established. Intracellularly, maltodextrin phosphorylase and 4-alpha-glucanotransferase occurred in both. Degradation of extracellular alpha-glucans was mediated by a mainly intracellular isoamylase in P. amyloderamosa, whereas P. saccharophila possessed an extracellular alpha-amylase and a firmly cell-bound pullulanase.