hormones and ecology 2013

This is our abstract for INTECOL 2013 (International ecology society)  

Soil microbial-community response to exogenous steroidal sex hormones under field conditions

G. Hermann^a,   L.S. Shore^b, Y. Steinberger^a,*

^aThe Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University,
Ramat-Gan 52900, Israel

^bKimron Veterinary Institute, Beit-Dagan, Israel

Abstract

Cattle manure contains a wide range of bio-active components and is widely used as an organic amendment in agroecosystems. One such group of bio-active components in manure that may induce abnormal development of the endocrine system in organisms is the sex hormones (estradiol, estrone, progesterone, testosterone). For example, very low levels of estrogen (ng/L) are needed to cause feminization in male fish while the concentration in cow manure is nearly 1000 µg/kg dry wt. We, therefore, determined the effect of the addition of steroids under field conditions on one of the major components of the soil milieu - soil microbial community, testing its respiration rate (CO₂ evolution) as well as activity following stimulation with glucose [microbial biomass (MB)], and the soil microbial community’s  ability to use steroid mammalian hormones [hormone utilization (H-U)]. Steroids (estradiol, estrone, and testosterone) were applied in environmentally relevant concentrations dissolved in 2.5 l water on 0.25 m² plots in triplicate, and comparison was made with plots receiving water alone. Soil samples were taken from the 0-5, 5-10, and 10-20–cm soil layers. MB, CO₂ evolution, and H-U ability were examined at five different times post-treatment (0.5, 3, 4, 5, and 25 days).  Significantly higher MB and CO₂ production were found all five times in the upper soil level but not in the lower soil levels (estradiol=estrone>testosterone). The addition of steroids in vitro to the soil samples with prior exposure in situ resulted in increased CO₂ production by upper-soil–level samples but generally a lower utilization of steroids in the lower strata. Our study suggest that the increase in MB seen under field conditions in the upper soil level following exposure to steroids is the result of increased capacity of the soil bacteria to mineralize the steroids.