Uncultured bacterial diversity in tropical maize (Zea mays L.) rhizosphere

Structure of maize (Zea mays L.) rhizosphere bacteria was evaluated to explore the feasibility of identifying novel rhizosphere bacteria using culture-independent method based on direct amplification and analysis of 16S rRNA gene (rRNA) sequences and especially to obtain a better understanding of bacterial community structure and diversity from maize. A total of 274 sequences were analyzed and assigned 48.00% Proteobacteria, 10.30% Actinobacteria, 9.90% Bacteroidetes, 6.60% Verrucomicrobia, 4.80% Acidobacteria, 1.80% Firmicutes, 1.50% Chloroflexi, 1.50% TM7, 1.10% Deinococcus-Thermus, 0.70% Planctomycetes, 0.70% Gemmatimonadetes and 0.40% Cyanobacteria. Economically important phyla Actinobacteria was second most dominant group after Proteobacteria, in our clone library. It would be interesting to hypothesize that root exudates from maize rhizosphere favors growth of Actinobacteria like microbes to eliminate pathogenic bacteria and decompose plant matter, for enhanced plant and soil health. An additional 12.8% of clone library (35 operational taxonomical units (OTUs) from 43 clones) with less than 94% similarity to any GenBank sequence could not be assigned to any known phylum and may represent unidentified bacterial lineages and suggests that a large amount of the rhizobacterial diversity remains to be characterized by culturing.