Recovery of soil microbial community structure and activity following partial sterilization with gamma irradiation

Hassi, Ummehani; Hu, Junwei; Sleutel, Steven

doi:10.1016/j.apsoil.2023.104839

Cited by 4 publications

(2 citation statements)

References 54 publications

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“…As an alternative, partial or selective sterilization is often preferred. This approach minimizes changes to both biotic and abiotic soil properties, maintaining a more realistic experimental system while still allowing some control (Hassi et al 2023 ; Querejeta 2023 ; Mocali et al 2022 ).…”

Section: Resultsmentioning

confidence: 99%

Competitive fitness and stability of ammonium-excreting Azotobacter vinelandii strains in the soil

Ambrosio,

Burgos Herrera,

Do Nascimento

et al. 2024

Appl Microbiol Biotechnol

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Non-symbiotic N2-fixation would greatly increase the versatility of N-biofertilizers for sustainable agriculture. Genetic modification of diazotrophic bacteria has successfully enhanced NH4+ release. In this study, we compared the competitive fitness of A. vinelandii mutant strains, which allowed us to analyze the burden of NH4+ release under a broad dynamic range. Long-term competition assays under regular culture conditions confirmed a large burden for NH4+ release, exclusion by the wt strain, phenotypic instability, and loss of the ability to release NH4+. In contrast, co-inoculation in mild autoclaved soil showed a much longer co-existence with the wt strain and a stable NH4+ release phenotype. All genetically modified strains increased the N content and changed its chemical speciation in the soil. This study contributes one step forward towards bridging a knowledge gap between molecular biology laboratory research and the incorporation of N from the air into the soil in a molecular species suitable for plant nutrition, a crucial requirement for developing improved bacterial inoculants for economic and environmentally sustainable agriculture. Key points • Genetic engineering for NH4+ excretion imposes a fitness burden on the culture medium • Large phenotypic instability for NH4+-excreting bacteria in culture medium • Lower fitness burden and phenotypic instability for NH4+-excreting bacteria in soil

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Section: Resultsmentioning

confidence: 99%

Competitive fitness and stability of ammonium-excreting Azotobacter vinelandii strains in the soil

Ambrosio,

Burgos Herrera,

Do Nascimento

et al. 2024

Appl Microbiol Biotechnol

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show abstract

“…Gamma irradiation requires highly specialized facilities and equipment, but has been described by some as a “gold standard,” as it is thought to cause fewer substantial changes to some soils during sterilization ( 17 , 19 , 20 ). Nonetheless, gamma irradiation is not well borne out across a wide range of soil types ( 21 ) and may not biotically clear soils better than autoclaving ( 19 ). Similar to other sterilization methods, gamma irradiation alters the physical and chemical properties of soil, including the release of highly reactive free radicals and changes to the structure of organic matter, among others ( 17 , 22 ).…”

Section: Introductionmentioning

confidence: 99%

Autoclaving is at least as effective as gamma irradiation for biotic clearing and intentional microbial recolonization of soil

King,

Grandinette,

Trase

et al. 2024

mSphere

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Sterilization is commonly used to remove or reduce the biotic constraints of a soil to allow recolonization by soil-dwelling organisms, with autoclaving and gamma irradiation being the most frequently used approaches. Many studies have characterized sterilization impacts on soil physicochemical properties, with gamma irradiation often described as the preferred approach, despite the lower cost and higher scalability of autoclaving. However, few studies have compared how sterilization techniques impact soil recolonization by microorganisms. Here, we compared how two sterilization approaches (autoclaving; gamma irradiation) and soil washing impacted microbial recolonization of soil from a diverse soil inoculum. Sterilization method had little impact on microbial alpha diversity across recolonized soils. For sterile soil regrowth microcosms, species richness and diversity were significantly reduced by autoclaving relative to gamma irradiation, particularly for fungi. There was no impact of sterilization method on bacterial composition in recolonized soils and minimal impact on fungal composition ( P = 0.05). Washing soils had a greater impact on microbial composition than sterilization method, and sterile soil regrowth had negligible impacts on microbial recolonization. These data suggest that sterilization method has no clear impact on microbial recolonization, at least across the soils tested, indicating that soil autoclaving is an appropriate and economical approach for biotically clearing soils. IMPORTANCE Sterilized soils represent soil-like environments that act as a medium to study microbial colonization dynamics in more “natural” settings relative to artificial culturing environments. Soil sterilization is often carried out by gamma irradiation or autoclaving, which both alter soil properties, but gamma irradiation is thought to be the gentler technique. Gamma irradiation can be cost prohibitive and does not scale well for larger experiments. We sought to examine how soil sterilization technique can impact microbial colonization, and additionally looked at the impact of soil washing which is believed to remove soil toxins that inhibit soil recolonization. We found that both gamma-irradiated and autoclaved soils showed similar colonization patterns when reintroducing microorganisms. Soil washing, relative to sterilization technique, had a greater impact on which microorganisms were able to recolonize the soil. When allowing sterilized soils to regrow (i.e., persisting microorganisms), gamma irradiation performed worse, suggesting that gamma irradiation does not biotically clear soils as well as autoclaving. These data suggest that both sterilization techniques are comparable, and that autoclaving may be more effective at biotically clearing soil.

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Increased N2O emissions by the soil nematode community cannot be fully explained by enhanced mineral N availability

Hu,

Kong,

Francoys

et al. 2024

Soil Biology and Biochemistry

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Recovery of soil microbial community structure and activity following partial sterilization with gamma irradiation

Cited by 4 publications

References 54 publications

Competitive fitness and stability of ammonium-excreting Azotobacter vinelandii strains in the soil

Competitive fitness and stability of ammonium-excreting Azotobacter vinelandii strains in the soil

Autoclaving is at least as effective as gamma irradiation for biotic clearing and intentional microbial recolonization of soil

Increased N2O emissions by the soil nematode community cannot be fully explained by enhanced mineral N availability

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