Survival of E. coli TVS353 in Soil Mesocosms at Various Moisture Levels and Light Exposure in Controlled Environments

Light exposure is an important factor influencing the Escherichia coli survival in agricultural soils. This study evaluated the combined effects of soil moisture and light exposure on the survival of E. coli in agricultural soil under a controlled diurnal environment. For this, soil mesocosms were inoculated with E. coli TVS353 and maintained at three moisture levels (100%, 75%, and 50% field capacity (FC)) and two light conditions (diurnal and complete dark), with a 14 h day at 25 ℃ and a 10 h night at 15 ℃. Soil samples were enumerated for E. coli on days 0, 1, 3, 7, 14, 28, 35, 56, and every 7 days thereafter, and survival dynamics were analyzed using linear mixed-effect analysis and a biphasic microbial survival model. Across all treatments, E. coli declined significantly over time (p < 0.0001). Overall, E. coli survived up to 140 days under higher soil moisture levels (100% and 75% FC) and in dark conditions, whereas survival was 63 to 70 days at 50% FC in the diurnal environment. Biphasic survival modeling revealed higher initial inactivation rate constants under low-moisture and low-light exposure conditions. This study represents one of the first attempts to quantitatively assess the effect of light exposure on E. coli survival in agricultural soils across varying moisture levels.