Worm, J. Royal Vet. and Agricult. Univ., jaw@kvl.dk
Jensen, L. Royal Vet. and Agricult. Univ., lej@kvl.dk
Nybroe, O. Royal Vet. and Agricult. Univ., oln@kvl.dk
Søndergaard, M. Univ. of Copenhagen, flab@inet.uni-c.dk

Proteinase activity represents a central function with respect to the cycling of organic material. Obviously, protein degradation is facilitated when proteolytic bacteria are present and produce extracellular protease. It is less clear if protein hydrolysates are available for non-proteolytic bacteria, and how these functional groups may interact. The proteolytic P. fluorescens ON2-wt and a proteinase deficient mutant ON2-Pd5 were used to demonstrate the role of proteinase in protein degradation and nitrogen mobilization. A non-proteolytic P. fluorescens reporter strain, DF57-N3, expressing bioluminescence in response to nitrogen limitation, monitored nitrogen availability. DF57-N3 was co-cultured with either ON2-wt or ON2-Pd5 in medium conducive for proteinase expression containing glucose and casein in a ratio calibrated to result in nitrogen limitation in the absence of proteinase activity. Proteinase activity enhanced the growth of the culture and reduced the nitrogen starvation response, indicating proteinase dependent mobilisation of the casein including cross-feeding with nitrogen. Competition between proteolytic and non-proteolytic strains were observed to affect both growth and proteinase production. Hence, in this model community the availability of protein substrate was influenced by the relative abundance of proteolytic and non-proteolytic bacteria. Proteolytic activity was required to mobilize nitrogen sources and thereby relieve nitrogen starvation of a non-proteolytic organism, demonstrating competition between functional groups.
Day: Tuesday, Feb. 2
Time: Poster
Location: Sweeney Center
Code: SS40TU0376S