Naslov
Structural and functional diversity of proteolytic genes in an arable field

Autori
Mrkonjić Fuka, Mirna

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Lehrstuhl fur Bodenoekologie

Mjesto
Munich

Datum
02.05

Godina
2007

Stranica
93

Mentor
Munch, Jean Charles

Neposredni voditelj
Schloter, Michael

Ključne riječi
soil proteolytic activity; subtilisin; neutral metalloprotease; 16S rRNA; T-RFLP; Real-Time PCR

Sažetak
The aim of the present study was to increase our knowledge on proteolytic processes in agricultural soils. Diversity, abundance and activity of proteolytic populations were investigated with respect to spatial, temporal and vertical variability of naturally occurring environment factors. For this purpose an arable field in Southern Germany under integrated management was studied. The uniformly managed field shows pronounced soil heterogeneity with four different soil types. In April, July and October 2003 soil samples were taken from the four soil types at three different depths, up to 40 cm, according to the horizontation of the soil. A cultivation-independent approach was applied. PCR was employed to detect the genes encoding for neutral metalloprotease (npr) and subtilisin (sub). Abundance of genes of interest was estimated by the Real-Time PCR whereas potential proteolytic activity was measured by transformation of added substrate. The number and activity of respective genes showed high vertical, spatial and seasonal variation due to the variable physicochemical characteristics of investigated soils. Mainly factors as substrate availability and soil texture were responded for observed changes. Additionally, mineral fertilizer application, soil cultivation and seasonal variation in temperature or soil moisture influenced the size and activity of proteolytic community. First characterization of proteolytic bacterial community composition of the investigated soil samples was done by T-RFLP fingerprinting analysis. The structure of npr or sub communities was as well affected by vertical, spatial and seasonal variation. To obtain detailed information about the structure of the soil npr coding bacterial community, cloning and analyzing of npr PCR products were performed. Clone libraries were generated from the topsoil samples collected in July. Phylogenetic analysis of the soil npr sequences revealed that most clones have a poor homology to isolates previously obtained from various environments. Cloned npr sequences were highly diverse and spread through the whole phylogenetic group of npr sequences. The present study revealed a hitherto unknown diversity of proteolytic genes in the agricultural soil at the investigated study site. However, phylogenetic tree organization indicated that the four proteolytic npr soil communities are related with some overlap. Overall the results indicate considerable influence of soil physicochemical properties, management practice during the season and climatic seasonal changes on soil proteolytic community structure and function. Varied environmental conditions caused variability in the size, structure and activity of proteolytic community at the sites under investigation.

Izvorni jezik
Engleski

Znanstvena područja
Poljoprivreda (agronomija)

POVEZANOST RADA