Bacterial Composition and Diversity During Lignocellulosic Decomposition.

Decomposition of organic materials in the soil has been widely studied. However, there is scarce and limited information on bacterial diversity and dynamics associated with lignocellulose decomposition. Thus, this study was conducted to understand bacterial colonization throughout decomposition and to know how bacterial community dynamics is affected by soil and residue types during lignocellulosic decomposition. 16S rRNA clone libraries were constructed from the detritusphere (residues and adhering soil) samples from a 3 x 2 x 4 factorial experiment consisting of 3 residue amendments (without residue, switch grass straw, rice straw); 2 soil types (Sharkey and Marietta series); and 4 incubation periods (3, 18, 44 and 120 days; 25^oC).  A total of 1389 clones produced 481 operational taxonomic units (OTU; D=0.03). The dominant bacterial phylotypes (class-level) associated with lignocellulosic decomposition were Bacilli (39.34% of the total clones), Sphingobacteria (15.96%), Gammaproteobacteria (12.79%), Alphaproteobacteria (11.7%) and Betaproteobacteria (9.12%). The multi-response permutation procedures (MRPP), a nonparametic procedure for testing the hypothesis of no difference between two or more groups of entities, revealed that bacterial communities were significantly differed across incubation periods (P=0.00000) and soil types (P=0.0077) while there was no significant difference between residue types (P=0.24341). Results indicate that bacterial communities associated with lignocellulosic decomposition represent a subset of the soil bacterial diversity. The factors influencing the community dynamics (e.g. microbial interactions, residue chemistry) need further investigation.