Abstract

The soil bacterial communities in response to aluminum (Al) treatments were evaluated by polymerase chain reaction-amplified restriction fragment length polymorphism (PCR-RFLP) of 16S rRNA genes in acidic red soil samples in this study. A total of 6 bacterial communities were sampled from two representative soil types under different Al-treated concentrations. Bacterial genomic DNA was extracted and nested PCR-amplified to obtain 16S rDNA fragments which were cloned to construct 6 16S rDNA libraries. Clones of each library were selected randomly for PCR-RFLP analysis of rDNA fragments, and eventually 60 genotypes were identified by RFLP fingerprinting. These 60 genotypes were sequenced and their respective phylotype was identified through the Basic Local Alignment Search Tool (BLAST) of NCBI (similarity 93 to 100%) and phylogenetic analyzed. The phylotype richness, frequency distribution (evenness) and composition of the clone libraries were investigated by using a variety of diversity indices. Among these phylotypes, 96.7% belonged to the genera α-, β-, γ-, δ- Proteobacteria, Acidobacteria, Cytophaga-Flavobacteria-Bacteroides (CFB group), green nonsulfur (GNS) bacteria, Gemmatimonadetes, high seed sludge (GC) Gram-positive and Nitrospira. Sequence analyses revealed that 56.7% (34) of clone sequences were similar to those of uncultured soil bacteria in the environment. In addition, the bacterial diversities and compositions were clearly displayed in different soil samples. More genera were discovered in A₀ soil sample than any other, and some special species, such as Nitrospira, disappeared in Al-treated soils.

Key words: Acidic red soil, aluminum stress, soil bacteria, 16S rDNA, restriction fragment length polymorphism (RFLP)