Updating the sequence based classification of glycosyl hydrolases Adult chat free trial online
The strong similarity between different glycosyl hydrolases of rumen fungi and bacteria suggests that most, if not all, of the glycosyl hydrolases of rumen fungi that play an important role in the degradation of cellulose and other plant polysaccharides were acquired by horizontal gene transfer events.
This acquisition allows fungi to establish a habitat within a new environmental niche: the rumen of the herbivorous mammals for which cellulose and plant hemicellulose constitute the main raw nutritive substrate.
So far, a number of genes and/or c DNAs which encode endoglucanases, exoglucanases, xylanases, lichenases, and mannanases have been cloned and sequenced from different species, including the anaerobic fungi Most of the fungal GH sequences derived from these genes contain a dockerin-like reiterated sequence that mediates the assembly of a large multienzyme cellulosome-like complex (Fanutti et al.
1995 ) which exhibits very high cellulase activity against crystalline cellulose (Wilson and Wood 1992 ) and is similar to that described for (Beguin and Lemaire 1996 ) and other bacteria (Karita, Sakka, and Ohmiya 1997 ).
As a measure of the distance between the codon usage of a gene (), we calculated the Hamming distance following a procedure similar to the one used for predicting protein structural classes (Chou and Zhang 1995 ).
Applying the principle of G C content analysis should also allow the detection of horizontal gene transfer.
Multiple alignments, with final manual adjustments, and phylogenetic analysis were performed using the CLUSTAL W software package (Jeanmougin et al. Bootstrap values were calculated in 1,000 replicates.
The mean value of the total G C content of the 35 rumen genes was 39.9 ± 4.1%.
The normal microbiota in this anoxic environment are composed of bacteria, ciliate and flagellate protozoa, and anaerobic chytridiomycete fungi (Flint 1997 ; Gordon and Phillips 1998 ).
Because cellulose and plant hemicellulose are the most abundant carbon and energy source in the rumen, the glycosyl hydrolases (GHs) of these organisms must play a significant role in their homeostasis.