This study investigates the effects of compost fermented with thermophilic Bacillaceae on carrot growth and quality. The researchers found that compost significantly increased carrot productivity, antioxidant activity, color, and taste, and altered soil bacterial composition and metabolite levels. Structural equation modeling (SEM) revealed key links between amino acids, antioxidant activity, flavonoids/carotenoids in plants and compost exposure, and between *Paenibacillus* and nitrogen compounds in the soil. Genome analysis of compost-derived *Paenibacillus* isolates supported these findings, suggesting a complex cascade of plant growth-promoting effects and nitrogen cycle modulation.

Hirokuni Miyamoto, Katsumi Shigeta, Wataru Suda, Yasunori Ichihashi, Naoto Nihei, Makiko Matsuura, Arisa Tsuboi, Naoki Tominaga, Masahiko Aono, Muneo Sato, Shunya Taguchi, Teruno Nakaguma, Naoko Tsuji, Chitose Ishii, Teruo Matsushita, Chie Shindo, Toshiaki Ito, Tamotsu Kato, Atsushi Kurotani, Hideaki Shima, Shigeharu Moriya, Satoshi Wada, Sankichi Horiuchi, Takashi Satoh, Kenichi Mori, Takumi Nishiuchi, Hisashi Miyamoto, Hiroaki Kodama, Masahira Hattori, Hiroshi Ohno, Jun Kikuchi, Masami Yokota Hirai