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Related Experiment Videos

Mutation in Escherichia coli during substrate-accelerated death.

D Savva

    Microbios
    |January 1, 1980
    PubMed
    Summary

    Substrate-accelerated death in Escherichia coli is linked to low cyclic AMP (cAMP) levels. Supplementing with cAMP protected trp- cells from death during starvation, suggesting cAMP

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    Area of Science:

    • Microbiology
    • Molecular Biology
    • Bacterial Physiology

    Background:

    • Substrate-accelerated death (SAD) is a phenomenon where bacterial populations decline despite nutrient availability.
    • Escherichia coli trp- strains exhibit increased reversion to trp+ during starvation, a process linked to cell death.
    • Cyclic AMP (cAMP) is a crucial signaling molecule involved in various cellular processes, including stress responses.

    Purpose of the Study:

    • To investigate the role of cyclic AMP (cAMP) in substrate-accelerated death (SAD) of Escherichia coli.
    • To determine the relationship between cAMP levels and the increased reversion rate of trp- to trp+ during starvation.
    • To explore potential mechanisms underlying SAD, including DNA repair pathways.

    Main Methods:

    • Studying lactose-limited cultures of Escherichia coli WP2 trp- and E. coli WP2 trp+ under starvation conditions.
    • Monitoring viable cell counts and the number of trp+ revertants.
    • Supplementing starvation media with 7.5 mM-cAMP and various antibiotics (benzyl penicillin, nalidixic acid, novobiocin, rifampicin).

    Main Results:

    • During starvation, E. coli WP2 trp- viable counts decreased while trp+ revertants increased.
    • Addition of cAMP prevented trp- cell death but did not affect the increase in trp+ revertants.
    • Starvation of pure trp+ revertant cultures did not result in cell death, suggesting lower cAMP levels in trp- cells.
    • Antibiotics did not affect viable counts, ruling out cryptic growth or DNA replication.
    • Novobiocin inhibited the increase in trp+ revertants, hinting at a role for DNA repair.

    Conclusions:

    • Lower intracellular cAMP levels in trp- cells may contribute to substrate-accelerated death during starvation.
    • The increase in trp+ revertants during starvation is independent of cell death but may be influenced by DNA repair mechanisms.
    • A constitutive error-prone DNA repair mechanism is a potential factor in the observed trp+ reversion.

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