Diversity of proteolytic community encoding for subtilisin in an arable field: spatial and temporal variability

The diversity of soil proteolytic community encoding for subtilisin (sub) was investigated at a cultivated field site with four different soil types and at three different depths in April, July, and October. A terminal restriction fragment length polymorphism (T-RFLP) analysis of subtilisin gene (sub) was applied to study dynamic of the sub gene pool. The aim of the present study was to relate differences in sub community structure to the vertical, site, and seasonal variations naturally occurring at the field site under investigation. A significant spatial variability in the community structure of sub-containing bacteria was observed. The richness of sub proteolytic bacterial population decreased with increasing soil depth, revealing the highest values in upper layers. A similar trend was observed among the different sites; the highest diversity was noticed at the site with the highest silt and nutrient content. The reasons behind the observed patterns in the community structure might be varying water amount and spatial isolation along the soil profile as well as variability of the quantity and quality of available substrates among different depths and different sites.