Tue may 27th ,  2.30pm, conference room INRA (SDAR building)

Joy Watts (University of Portsmouth, UK)

The armoured catfish, Panaque nigrolineatus, has specialized physiological adaptations to enable high levels of wood to be ingested in its diet. However, it is unclear what nutritional benefit is derived or the nature of any symbiosis that facilitates it.  In the present study, we examined microbial communities associated with the foregut, midgut, hindgut, and auxiliary lobe of P. nigrolineatus using a metagenomic approach utilizing 454 pyrosequencing.  Microbial community diversity altered in the different regions of the GI tract indicating different functional roles of key bacterial populations.  To complement this genetic approach, scanning electron microscopy of the different regions of the gastrointestinal tract was performed to examine the microbial community present.  Lignocellulose degradation within the gastrointestinal tract was supported by scanning electron microscopy observations, indicating structural alterations in the wood.  Furthermore, the wood particles in the hindgut appeared to harbour assemblies suggestive of microbial cells.  Additionally, wood collected from different regions of the GI tract was analyzed using Fourier-Transformed Infrared (FTIR) spectroscopy.  This technique revealed changes to the wood associated with gut transit.  These changes are consistent with the presence of a wood-digesting activity within the GI tract within the P. nigrolineatus gastrointestinal tract.  Furthermore, using fixed GI tract tissue using catalyzed reporter deposition enhanced immunofluorescence revealed the highest densities of nitrogenase-containing cells attached to the woody digesta within the GI tract with fewer cells sparsely colonizing the intestinal mucous layer.  These findings are consistent with a role for the P. nigrolineatus intestinal tract microbial community in providing a source of fixed nitrogen under nitrogen limiting conditions.