CeBiTec Colloquium

 date 

Monday, March 15th 2010, 17 c.t.

 location 

G2-104, CeBiTec Building

 speaker 

Prof. Dr. J.D. van Elsas

Department of Microbial Ecology,
University of Groningen (Netherlands)

 title 

Do soil fungi provide hospitable microhabitats for soil bacteria?

  Variovorax paradoxus strain HB44, next to Burkholderia terrae BS001 and Dyella japonica BS003, were found to be positively selected in the mycosphere of the tricholomateceous fungi Laccaria proxima and/or Lyophyllum sp. strain Karsten in an acid soil denoted G. We provide strong evidence for the poor survival of these organisms in G soil. In contrast, the survival rate of strain HB44 in two other soils, with pH values >5.5, was significantly raised. Moreover, clearly enhanced strain HB44 survival in soil G was found if the pH of the G soil was raised to 5.5 or higher. Persistence or even growth (in the presence of an exogenous carbon source, glycerol) was noted at pH values of 5.5 or 6.5 in the G soil. Strikingly, Lyophyllum sp.strain Karsten, when colonizing sterilized G soil, significantly raised the soil pH from about 4.6 to 5.0. The pH raise was dependent on time, hyphal development, as well as on initial soil pH, but was consistent throughout. Thus, the modulated soil pH conditions were shown to be permissive for the survival and growth of strain HB44, and this was extended to strains BS001 and BS003. Specifically, strain HB44 was shown to consistently grow, at the expense of exogenous carbon, only at pH values > 5.0. These findings corroborate the hypothesis that L. sp. strain Karsten provides a suitable niche for acid-sensitive strains like HB44, BS001 and BS003 in its mycosphere in acid soil, which is strongly defined by the establishment of a growth-permissive pH.
 host 

Prof. Dr. Alfred Pühler