Population dynamics of cellulolytic bacteria depend on the richness of cellulosic materials in the habitat

Abstract

Bacterial diversity and hydrolytic enzyme activity of paddy soil, paddy soil mixed with cow dung, and paddy soil mixed with cow dung and rice straw samples were studied. A total of twelve different bacterial species were found by 16S rDNA sequence analysis, viz., Bacillus subtilis, Streptomyces colombiensis, Paenibacillus polymyxa, Staphylococcus pasteuri, B. aquimaris, B. licheniformis, B. amyloliquefaciens, Microbacterium testaceum, P. illinoisensis, Micrococcus sp., B. subtilis, Rhizobium tropici, Micrococcus luteus, Bacillacea bacterium, Microbacteriaceae bacterium, B. megaterium. The bacterial strains of the samples were divided into three phyla, namely Firmicutes, Actinobacteria, and Proteobacteria. The population of bacteria under the phylum Firmicutes was highest in all the samples. In addition, the population of bacteria under Firmicutes was gradually increased from the paddy soil sample (60%) to the paddy soil mixed with cow dung and rice straw samples (84%). On the other hand, the population of the bacteria under the phyla Actinobacteria and Proteobacteria gradually decreased from 28 and 12% of paddy soil to 11 and 5% of paddy soil mixed with cow dung and rice straw, respectively. The population of bacteria showing cellulase, xylanase, lichinase, and mannase activity were lowest in normal paddy soil (57, 53, 50 and 18%, respectively), except amylase were lowest in soil samples mixed with cow dung (39%); however, they gradually increased and were highest in the sample of paddy soil mixed with cow dung and rice straw (100, 100, 65, 54, and 61%, respectively). So it was observed that soil samples mixed with cow dung and rice straw may be a good source of plant cell wall degrading bacteria.