Comparative characterization of chitinolytic activity in five STREPTOMYCES strains and the metabolomic response of S. BAARNENSIS assi-23tb to phytopathogens IN PLANTA

Abstract

The wide species diversity of chitinolytic actinomycetes producing secondary metabolites and hydrolytic enzymes offers opportunities for effective soil biocontrol aimed at protecting plants from phytopathogens and preserving soil biodiversity. This study examined the chitinolytic potential of five soil actinomycete strains from the genus Streptomyces(S. flavovirens TT, S. sindenensis TK, S. baarnensis assi-23TB, S. anulatus TG, and S. xiamenensis TB) through integrated analytical and molecular biological approaches.The study demonstrated that the fundamental mechanism of Streptomycesstrain adaptation to chitin utilization is the targeted induction of functional chitinase genes.We identified distinct genome activation strategies and observed that high genetic activity leads to a robust physiological response, including active biomass accumulation and CO₂ emission. These findings confirm the high competitiveness of the investigated strains under conditions of limited access to readily available carbon and nitrogen sources. The study elucidated the interaction of the target strain Streptomyces baarnensis assi-23TB (VKPM Ac-2228) with two specific phytopathogens in both in vitro and in planta systems, using wheat seedlings (Triticum aestivum L. cv. Arkhat) and microclonal potato plants (Solanum tuberosum L. cv. Romano) as host models. A comparative analysis was performed to correlate the metabolic capabilities of S. baarnensis assi-23TB, as theoretically predicted by bioinformatic tools (antiSMASH, PATRIC), with its actual phenotypic metabolite production. The strain exhibited significant chitinolytic activity. Our analysis revealed dibutyl phthalate (DBP) to be a constitutive secondary metabolite responsible for the baseline antimicrobial activity.Notably, several predicted biosynthetic gene clusters (10-epi-HSAF, keivymicin, alkylresorcinol, desferrioxamine B, naringenin, and zeatin) remained in a "silent" state under the experimental conditions. We found that the S. baarnensis exometabolome strictly depends on the presence of the host plant and specific pathogens (Fusarium graminearum and Phytophthora infestans). The association with wheat exclusively triggers the synthesis of the phytostimulant putrescine and energy metabolism regulators, such as lactic and succinic acids. This symbiotic system also drives the production of amino acids, sugars, and myo-inositol.The study experimentally confirms the multifunctionality of the Streptomyces baarnensis assi-23TB strain, which integrates direct enzymatic lysis of pathogens with the biochemical stimulation of plant growth and adaptive responses