SUBSTRATE UPTAKE AND UTILIZATION BY A MARINE ULTRAMICROBACTERIUM

F SCHUT, M JANSEN, TMP GOMES, JC GOTTSCHAL, W HARDER, RA PRINS

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    Abstract

    A facultatively oligotrophic ultramicrobacterium (strain RB2256) isolated from an Alaskan fjord by extinction dilution in seawater, was grown in batch culture and under single- and dual-substrate-limitation of alanine and glucose in a chemostat. The nature of the uptake systems, and the uptake kinetics and utilization patterns of alanine and glucose were investigated. Glucose uptake was inducible, the system exhibited a narrow substrate specificity, and part of the uptake system was osmotic-shock-sensitive. Half-saturation constants for glucose were between 7 and 74 mu M during glucose limitation. The initial step in glucose metabolism was the synthesis of sugar polymers, even during glucose-limited growth. The alanine uptake system was constitutively expressed and was binding-protein-dependent. In addition to L-alanine, nine other amino acids inhibited accumulation of [C-14]L-alanine, indicating broad substrate specificity of the alanine transporter. Half-saturation constants between 1.3 and 1.8 mu M were determined for alanine uptake during alanine limitation, Simultaneous utilization of glucose and alanine occurred during substrate-limited growth in the chemostat, and during growth in batch culture at relatively high (mM) substrate concentrations. However, the half-saturation constant for alanine transport during dual-substrate-limitation, i.e. in the presence of glucose, increased almost fivefold. We conclude that mixed substrate utilization is an inherent property of this organism.

    Original languageEnglish
    Pages (from-to)351-361
    Number of pages11
    JournalMicrobiology-Uk
    Volume141
    Publication statusPublished - Feb-1995

    Keywords

    • OLIGOTROPHY
    • ULTRAMICROBACTERIA
    • GLUCOSE
    • ALANINE
    • UPTAKE SYSTEMS
    • ESCHERICHIA-COLI
    • GROWTH-KINETICS
    • BACTERIOPLANKTON GROWTH
    • STARVATION-SURVIVAL
    • SEAWATER CULTURES
    • LIMITED GROWTH
    • D-GLUCOSE
    • BACTERIA
    • TRANSPORT
    • PROTEIN

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