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Microorganisms play a crucial role in agriculture and the food industry, contributing to soil fertility, crop protection, and food production. Their functions range from nitrogen fixation and biopesticide production to fermentation and food preservation, making them indispensable to sustainable farming and food safety.Role in AgricultureNitrogen-fixing bacteria, such as Rhizobium (symbiotic) and Azotobacter (free-living), convert atmospheric nitrogen into ammonia through biological nitrogen...
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A photoelectric method for counting microorganisms.

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A protein factor in the nutrition of Paramecium caudatum.

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Related Experiment Video

Updated: Jun 15, 2026

Breast Milk Enhances Growth of Enteroids: An Ex Vivo Model of Cell Proliferation
09:02

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Published on: February 15, 2018

PROBIOTICS: GROWTH-PROMOTING FACTORS PRODUCED BY MICROORGANISMS.

D M LILLY, R H STILLWELL

    Science (New York, N.Y.)
    |February 12, 1965
    PubMed
    Summary

    Certain protozoa species release growth-promoting substances. These factors extend the logarithmic growth phase in other protozoa, like Tetrahymena pyriformis, by up to 50%.

    Area of Science:

    • Microbiology
    • Cell Biology
    • Protozoology

    Background:

    • Protozoa exhibit complex growth dynamics during logarithmic phases.
    • Inter-species interactions can influence microbial population growth.
    • Growth factors and inhibitors play critical roles in microbial ecology.

    Purpose of the Study:

    • To investigate the production of growth-promoting substances by protozoa.
    • To determine the effect of these substances on the logarithmic growth phase of other protozoa species.
    • To quantify the growth enhancement mediated by inter-species protozoan factors.

    Main Methods:

    • Culturing of protozoa species, including Colpidium campylum and Tetrahymena pyriformis.
    • Collection and application of extracellular substances produced during logarithmic growth.
    Keywords:
    CILIATACULTURE MEDIAEXPERIMENTAL LAB STUDYGROWTH SUBSTANCESMETABOLISMPEPTIDESPHARMACOLOGYTETRAHYMENA

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  • Measurement of growth rates and logarithmic phase duration in response to tested substances.

    • Main Results:

    • Several protozoa species secrete factors that prolong their logarithmic growth phase.
    • Tetrahymena pyriformis demonstrated a consistent 50% increase in growth when exposed to a factor from Colpidium campylum.
    • The observed growth promotion is distinct from antibiotic-mediated growth inhibition.

    Conclusions:

    • Protozoa can produce and release beneficial compounds that enhance the growth of other protozoa.
    • These findings highlight a novel mechanism of inter-species cooperation in protozoan communities.
    • The identified growth factors have potential applications in microbial cultivation and biotechnology.