###### Abstract  
This study compared the physiological effects at a metabolomics level with autonomic nervous system responses in adults during soil mixing activities, based on the presence or absence of _Streptomyces rimosus_ in the soil. Thirty adult participants performed soil mixing activities for 5 min using sterilized soil with culture media and _Streptomyces rimosus_, respectively. Blood samples were drawn twice from each participant after each activity. Electroencephalograms were measured during the activity. Serum metabolites underwent metabolite profiling by gas chromatography, followed by multivariate analyses. Serum brain-derived neurotrophic factor and C-reactive protein levels were measured by Enzyme-Linked Immunosorbent Assay. Soil-emitted volatile organic compounds were identified via solid-phase microextraction and gas chromatography-mass spectroscopy, followed by multivariate analyses. The volatile compound analysis revealed that the terpenoid and benzoid compounds, geosmin, and 2-methylisoborneol were greater in soil with _Streptomyces rimosus_. Serum metabolomics revealed that the treatment group (soil inoculated with _Streptomyces rimosus_) possessed relatively higher levels of serotonin compared to the control group (soil mixed with culture media), and serum C-reactive protein levels were significantly lower in the treatment group. In the treatment group, the electroencephalogram revealed that alpha band activity of the occipital lobe increased. This study concludes that _Streptomyces rimosus_ soil contact can positively affect human metabolic and autonomic reactions. Therefore, this pilot study confirmed the possible role of soil microorganisms in horticultural activities for psychophysiological effects in humans. 202200  
belong to the group of terpenoid compounds and are synthesized by terpene synthetase, but they have different molecular formulas and structural arrangements [4]. In a previous study, as a result of inhalation of geosmin and 2-MIB in adults, cortical beta activity decreased and alpha activity increased, resulting in stabilization of brain waves [4]. Such positive olfactory stimulation has advantages such as reducing mental stress and improving relaxation and cognitive function [5; 6]. When a fragrance molecule is inhaled through the human nose, the inhaled fragrance molecule binds to the olfactory receptor, activates the olfactory receptor cell, transmits an electrical signal to the olfactory bulb through the neural network, and stimulates the hypothalamus and cerebral cortex through the process through the limbic system of the brain [7; 8; 9]. Odor molecules play an important role in human behavior such as emotions, thoughts, and memory by influencing spontaneous brain function through the olfactory system [10]. Aromatic compounds of plants have been reported to have various physiological effects on psychological aspects, emotional stability, and the nervous system [11; 12; 13]. However, there are still few studies on the effect of olfactory stimulation through soil and soil microorganisms on humans. One of these studies was conducted to identify the healing effect of contact with specific soil microorganisms. In that study, EEG analysis and serum metabolite profiling were performed to determine the psychophysiological effects of horticultural activities using soil inoculated with _Mycobacterium vaccae_ (_M. vaccae_), a soil microorganism belonging to Actinomycetes [14]. The study demonstrated that contact with the soil microorganism significantly affected the brain, metabolomics response, and autonomic nervous activities, with these changes inducing a state of relaxation in humans. Although it is generally known that the earthy-musty smell has an emotional stabilization effect, there have been few studies on the interaction between soil microorganisms and humans, and the healing mechanism has not been clearly revealed.