Abstract
Time-resolved utilization of multiple amino acids by Phaeobacter inhibens DSM
17395 was studied during growth with casamino acids. The 15 detected amino acids
could be grouped according to depletion rate into four different categories, i.e.
from rapid (category I) to nondepletion (category IV). Upon entry into stationary
growth phase, amino acids of category I (e.g. glutamate) were (almost) completely
depleted, while those of categories II (e.g. leucine) and III (e.g. serine) were
further consumed at varying rates and to different extents. Thus, cultures
entered stationary growth phase despite the ample presence of organic nutrients,
i.e. under nonlimiting conditions. Integrated proteomic and metabolomic analysis
identified 1747 proteins and 94 intracellular metabolites. Of these, 180 proteins
and 86 metabolites displayed altered abundance levels during growth. Most
strikingly, abundance and activity profiles of alanine dehydrogenase
concomitantly increased with the onset of enhanced alanine utilization during
transition into stationary growth phase. Most enzymes of amino acid and central
metabolism, however, displayed unaltered abundances across exponential and
stationary growth phases. In contrast, metabolites of the Entner-Doudoroff
pathway and gluconeogenesis as well as cellular fatty acids increased markedly in
abundance in early stationary growth phase.
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