The occurrence and identification of intracellular polyglucose storage granules in Methylococcus NCIB 11083 grown in chemostat culture on methane.

Abstract

The accumulation of intracellular storage granules (0.03--0.5 micrometer) by Methylococcus NCIB 11083 when grown under conditions of ammonia limitation with methane as the sole source of carbon and energy was inversely proportional to the dilution rate. The isolated material was composed entirely of glucose residues and the infra-red spectrum exhibited characteristic absorption bands at 925 cm(-1), 845 cm(-1) and 745 +/- 4cm(-1), indicating the presence of alpha (1 leads to 4) glycosidic linkages. The polymer dissolved in hot water to give an opalescent solution that formed a violet iodine complex with an absorption maximum at 550nm, identical to that observed with reference amylopectin. The percentage of the polysaccharide released as maltose by the action of beta- and alpha-amylases was 55--64% and 80--90% respectively, values very similar to those obtained by the action of these enzymes on reference amylopectin and glycogen. Methylation analysis indicated that the average interior and exterior chain lengths of the polymer were 2.7 and 10.0 glucose units respectively and confirmed that the Methylococcus polyglucose is a branched polymer composed of units joined by 1 leads to 4 and 1 leads to 6 linkages. The number average molecular weight of the polymer is 2--4.5 x 10(5). The stored polymer was metabolised by the organism and its metabolism resulted in the synthesis of protein.