Corynebacterium glutamicum: morphological and ultrastructural changes of l-lysine producing cells in continuous culture

Abstract

Corynebacterium glutamicum was observed to undergo several morphological and ultrastructural changes during a shift in dilution rate when grown in phosphate-limiting continuous culture. At 0.1 h−1 the cell culture appeared homogeneous and the average diameter of cells and the cell length was approximately 0.7 μm and 1–1.5 μm respectively. At 0.04 h−1 there was essentially no change in these readings, but at this dilution rate there was a significant proportion of cells that measured three times the original length. At six residence times the elongated cells were increasing in number, but these changes occurred without diminishing the system's performance. Some changes in cell ultrastructure were observed during the shift in dilution rate. Thus, the presence of polyphosphate granules and of glycogen appeared in the cytoplasm of producing cells (0.04 h−1). We have confirmed by mass spectrometry the absence of poly-β-hydroxybutyrate (PHB) in C. glutamicum.