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

Abstract

Appfled MicrobiologyBiotechnology © Springer-Verlag 1992 Summary. 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 gm and 1-1.5 gm respectively. At 0.04h -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 -l ) . We have confirmed by.mass spectrometry the absence of poly-~-hydroxybutyrate (PHB) in C. glutamicum.

Formation of volutin granules inCorynebacterium glutamicum

“…Both stress response and stationary‐phase adaptation also play a decisive role in the industrial production of amino acids with the aerobic Gram‐positive rod, Corynebacterium glutamicum [2]. Yet though corynebacteria, viz., C. diphtheriae and C. xerosis , were among the first organisms to be studied with regard to some key poly P enzyme functions [1], very little is yet known on the poly P metabolism in C. glutamicum : (i) Zhang et al [3] detected the gene sequence ppk2 , coding for a novel poly P kinase, in the genome of this organism; (ii) Ishige et al reported that the genes involved in the metabolism of pyrophosphate and polyphosphate were not affected by orthophosphate (P i ) starvation of C. glutamicum [4]; (iii) in a recent in vivo 31 P NMR study, Lambert et al [5] demonstrated the rapid accumulation of soluble intracellular poly P when oxygenated cell suspensions of C. glutamicum were spiked with glucose and P i ; this poly P pool of up to 300 mM (expressed in P‐units) decreases within minutes under anoxic conditions with concomitant increase of phosphorylated glycolytic intermediates [5]; (iv) transmission electron microscopic (TEM) pictures of C. glutamicum showed intracellular electron‐dense bodies that, without further experimental evidence, have been interpreted as granules consisting of poly P [6].…”

NCgl2620 Encodes a Class II Polyphosphate Kinase in Corynebacterium glutamicum

“…glutamicum is able to produce high amounts of soluble cytoplasmic poly P when cells are aerated and supplied with substrate and P i , and intracellular poly P granules (volutin) are formed preferentially in the early exponential phase of growth (6,18,22,28). Moreover, the poly P granules of C. glutamicum contain an enzyme predicted to be involved in poly P metabolism, i.e., a putative poly P glucokinase (6,18,22,28). To date, the enzymes involved in synthesis, conversion, and degradation of poly P have not been characterized in C. glutamicum.…”

Quantifying and directing metabolite flux: Application to amino acid overproduction

“…The basic principle is to assay whether certain values of easily accessible process parameters, like carbon dioxide evolution rate, oxygen uptake, growth characteristics or pH, correlate with peak activities in the desired yield performances. The strategy is then to try to hold these values of the extracellular parameters by environmental control, thereby extending the optimal flux situation within the cell [108,109]. Illustrative examples are the peak activities of specific lysine [110] or isoleucine [54] productivity with C.…”

“…Therefore, growth limitation is successfully applied for several amino acid overproduction processes. Growth limitation can be attained by limiting potassium, phosphate [109], manganese [111], for instance, or by use of an auxotrophy [112], and is usually combined with feeding of sugar. The feeding strategy can be used to optimize for maximum molar yield or maximum volumetric productivity [110].…”