Soil substrate source drives the microbes involved in the degradation of gelatin used as a biostimulant

Plant biostimulants improve crop yield and quality by stimulating plant nutrition processes and enhancing nutrient uptake efficiency, likely reflecting indirect effects mediated by beneficial soil microbes. Gelatin is an emerging plant biostimulant. Culture-dependent studies have identified several species of gelatin-degrading microbes, but the effect of gelatin on soil microbial communities in the absence of the plant microbiome has not been investigated. The objectives of this work were to evaluate changes in the microbial community induced by granulated gelatin amendments in different soils and substrates using high-throughput sequencing and to identify gelatin-hydrolyzing microbes for further application. Sandy soil, potting soil, paper plugs, black peat soil and pH-neutralized black peat soil were amended with gelatin and incubated at room temperature. After 7 and 15 days, samples were collected, DNA was extracted, and the bacterial and fungal communities were assessed by high-throughput sequencing of the 16S rRNA gene and the internal transcribed spacer (ITS) region, respectively. In parallel, microbes were isolated in culture medium. Regression analysis of shifts in the microbial communities demonstrated that the microbes positively impacted by gelatin amendment varied among the substrates, whereas few variations occurred between timepoints. The fungal genera Penicillium, Mortierella, Fusarium and Trichoderma and the bacterial genera Burkholderia, Pseudomonas and Rhodanobacter were among the microbes that increased in relative abundance in response to gelatin amendment. These microbes are efficient enzyme producers and are potential candidates for formulating beneficial microbial consortia that can be applied in tandem with gelatin to enhance its biostimulant activity.