Bacterial diversity in the Interstinal Tracts of the Fungus-Cultivating Termites Macrotermes michaelseni (Sjostedt) and Odontotermes somaliensis (Sjostedt

Abstract

Termites are an important group of insects that harbor a complex community of gut microbes, which contribute to digestion, termite nutrition and gas (methane, carbon dioxide and hydrogen) emission. The abundance of microbial communities in the intestinal tracts of two :fungus-cultivating termites Macrotermes michaelseni and Odontotermes somaliensis were examined using, the Most Probable Number (MPN) and plate count techniques and diversity was assessed by analysis of 16S rDNA genes using PCR. The microorganisms were isolated using an enriched media using either glucose, gelatin or cellulose as substrates. The highest number of microbes was in Macrotermes mic!!_qelseni and was recorded in KMMl medium giving a mean± SD of 173.5 ± 28.9 x 103 CFU/gut and a mean ± SD of 156 ± 25.45 x 103 CFU/gut in Odontotermes somaliensis by plate count technique. Using the MPN technique, the highest number of microbes was recorded in a KMMl medium giving approximately 43 x 104 cells/gut in Macrotermes michaelseni and in medium containing glucose an approximate of 480 cells/gut in Odontotermes somaliensis. Molecular studies were carried out by directly amplifying portions of the bacterial 16S ribosomal DNA (16S rDNA) genes from the mixed-population DNA of the microbial community in the termite gut by the PCR and these genes were clonally isolated. Analysis of the partial sequences of 16S rDNA showed the existence of bacteria species related to Proteobacteria, Cytophaga Flexibacter-Bacteroides, low G+C gram-positive bacteria, Anaerobaculum thermoterrenum and Spirochetes in both termites. Unique sequences showing very low sequence similarity to known 16S rDNA were also found. Phylogenetic analysis revealed that more the half of the clones isolated from Odontotermes somaliensis clustered with sequences from the Cytophaga-Flexibacter-Bacteroides group and few clones in Proteobacteria, low G+C gram-positive bacteria, Anaerobaculum thermoterrenum and Spirochetes groups. In Macrotermes michaelseni, the clones were well distributed in Proteobacteria, Cytophaga-Flexibacter-Bacteroides, and the low G+C gram-positive groups and very few clones related to Anaerobaculum thermoterrenum and Spirochetes groups. The results revealed an enormous diversity of bacteria in both termite species. Most of the clusters contained clones only from the respective termite species. The l 6S rDNA gene sequence data show that the majority of the intestinal micro:flora of Macrotermes michaelseni and Odontotermes somaliensis consists of new uncultured species previously unknown to microbiologists.