Disturbances change bacterial community
composition, but in many cases the new community perform as well as or better
than the undisturbed community. Thus, during a disturbance the community adapts
to new conditions by changes in abundance of OTUs and expression of relevant
genes. In some cases such as the input of dissolved organic matter
opportunistic bacteria succeed on the account of relatively slow growing oligotrohpic
bacteria. In this study the ability of soil bacterial communities, under
different mineral and organic input loads, to cope with a pulse disturbance of
heat shock was examined. The experiments were performed in mesocosem scale
using sandy soil irrigated with three water types of increasing mineral and OM
loads; fresh water with additional minerals (FW), treated wastewater with additional
minerals (TW) and artificial wastewater (AW) until a steady community was reached.
A pulse disturbance (heat shock) was applied and the following community’s
succession was documented. Soils were
analyzed using assays for biochemical activities and molecular techniques to
evaluate the active and total bacterial community’s composition and function. Results
show soil bacterial community stability was negatively related to the organic
carbon amended via the irrigation water. The bacterial communities in FW
irrigated soil showed the least change from the undisturbed soil bacterial
community composition and activities. These two parameters, bacterial community
composition and activity, changed significantly in AW samples irrigated with the
water of highest OM content. Further, the samples irrigated with AW, and to
some extent TW, showed higher sensitivity to heat shock than FW samples.
