Interaction effects of physicochemical factors on the growth of Burkholderia pseudomallei in soil microcosms

Background Burkholderia pseudomallei ( B. pseudomallei ), the causative agent of melioidosis, inhabits diverse ecological niches such as soil, surface water, and rhizospheres. Soil serves as its primary reservoir. Understanding the ecological niche of B. pseudomallei in soil is crucial for developing strategies to reduce bacterial presence. Therefore, this study investigated the interaction effects of soil parameters, namely pH, salinity, temperature, moisture content, carbon to nitrogen (C/N) ratio, and iron content, on B. pseudomallei proliferation through factorial microcosm experiments. Methodology/principal findings The experiments comprised three sets: (1) pH and salinity, (2) C/N ratio and salinity, and (3) iron content and salinity under varying temperature and moisture levels. Polynomial regression models demonstrated that all tested factors significantly influenced B. pseudomallei abundance, exhibiting linear, quadratic, cubic, and multi-way interactions. Optimal growth conditions varied with environmental context: B. pseudomallei growth peaked around pH 5 in the absence of salinity, whereas increased temperature and moisture expanded salinity tolerance (up to 0.61% at 35 °C and 75% moisture). The effect of C/N ratio on B. pseudomallei growth was moisture-dependent, the growth rate increased as the optimal C/N ratio rose from approximately 14–18 under 25 and 75% moisture, while elevated salinity consistently suppressed B. pseudomallei growth. Iron demonstrated contrasting effects depending on moisture; B. pseudomallei growth declined with increasing iron content at low-to-moderate moisture (25 and 50%) but was enhanced at high moisture (75%), with optimal iron content reaching 268.18 mg/kg at 35 °C. Conclusions/significance These findings highlight that B. pseudomallei proliferation is governed by multifactorial interactions among soil physicochemical parameters. Understanding these interactions may support the development of environmental management strategies to reduce B. pseudomallei persistence in soil.