Utilization of glutamate and glucose for heterotrophic growth by the marine pennate diatomNitzschia laevis
✍ Scribed by J. Lewin; J. A. Hellebust
- Publisher
- Springer-Verlag
- Year
- 1978
- Tongue
- English
- Weight
- 574 KB
- Volume
- 47
- Category
- Article
- ISSN
- 0025-3162
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✦ Synopsis
Nitzschia laevis H u s t e d t grew in the dark in the presence of either glutamate or glucose as substrate. Complex m i x t u r e s of yeast extract or tryptone plus lactate also supported good h e t e r o t r o p h i c growth, while tryptone alone only supported very slow growth in the dark. The o b s e r v e d growth rates of N. laevis in the dark at d i f f e r e n t c o n c e n t r a t i o n s of g l u t a m a t e or glucose could be a c c o u n t e d for by the m e a s u r e d uptake rates of these compounds. The affinity of the uptake systems for g l u t a m a t e and glucose (K s = 0.03 m M for each) was quite high, and similar for dark-and lightgrown cells. The lack of a lag-phase when cells were transferred from p h o t o a u t otrophic to h e t e r o t r o p h i c growth conditions can be e x p l a i n e d by the presence of uptake systems for glutamate and glucose in l i g h t -g r o w n cells, as well as in darkgrown cells. However, the uptake c a p a c i t y was g e n e r a l l y higher in the latter than the former. N. laevis also took up alanine and lactate a c c o r d i n g to M i c h a e l i s -M e n t e n kinetics, with a K s for alanine of 0.02 mM and for lactate of 0.4 mM. Malate and glycerol were not taken up to a s i g n i f i c a n t extent by the cells. Cells grown in continuous light had a d o u b l i n g time of 18 h. The shortest d o u b l i n g time observed in the dark on g l u t a m a t e was 48 h and on glucose 24 h. Glutamate was used for h e t e r o t r o p h i c growth with an efficiency of 43% and glucose with an e f f i c i e n c y of 48%.