A new approach to access as-yet-uncultured slow-growing microorganisms from saline and soil environments

Póster presentado en el XXX Congreso de la Sociedad Española de Microbiología, del 16 al 19 de junio de 2025, Jaén. Premio al mejor póster

Soils are very heterogeneous and the microbial communities of these environments present a very high diversity. Our capacity to culture the microorganisms from natural environments remains quite limited. Mostly, the fast-growing cells are easily cultured and often their growth mask the potential for fastidious prokaryotes to be detected in cultures. Herein, we propose a novel method for the selection, culture, and isolation of slow-growing microorganisms and we tested our approach using both saline and semi-arid soil samples. Target microorganisms were selected in a chemostat at a growth rate of 0.025 h -1 (28 d doubling time) on mineral media designed for methylotrophs (supplemented with methanol) or S-oxidizers (supplemented with thiosulfate). Different growth conditions (salinity, pH, temperature, and organic matter) were evaluated to select different microorganisms. Overtime, samples were collected and cells were isolated on Petri dishes with the corresponding growing medium and conditions. As a result, we managed to recover morphologically different strains. Cultured and isolated strains were preliminary identified by 16S rRNA gene amplification and sequencing. Outcomes indicated the identification of potential new species that will be taxonomically described using a polyphasic approach. The proposed strategy offers a novel, successful procedure to attempt to unravel the unknown structure of complex microbial dark matter communities in natural environments.

Pinar Yilmaz was supported by grant of 2219-International Post-Doctoral Research Fellowship Programme from The Scientific and Technological Research Council of Türkiye (TUBITAK), Project Number: 1059B192400183. Luis Soto was supported by a JAEICU-24-00754. Support was acknowledged from grants PID2024-150804NB-I00, PID2020-118136GB-I00, and PID2023-148654NB-I00.

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