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University of Nairobi (2012)

Screening for cellulosome signatures in schistocerca gregaria and coptotermes curvignathus gut bacteria

Khan, Nelson

Titre : Screening for cellulosome signatures in schistocerca gregaria and coptotermes curvignathus gut bacteria

Auteur : Khan, Nelson

Université de soutenance : University of Nairobi

Grade : Master of Science (MSc) 2012

Résumé
Cellulosomes are large extracellular multienzyme complexes produced by several cdlululytic , microorganisms, the first example of which was discovered in anaerobic, thermophilic . bacteria, Clostridium thermocellum. Cellulosomes are designed for efficient degradation of cellulose and associated plant cell wall material and thus provide a great potential for use in b\ocOOversion of lignocellulosic biomass to biofuel such as bin-ethannl and other chemicals Rational bioengineering of cellulosomal components for production of tailor-made ’designer cellulosome’ is now being developed for improved cellulose degradation. Development of . designer cellulosomes provides future breakthroughs necessary for their exploitation in industrial bioconversion of lignocellulose. These advances, combined with ecological and metagenomic studies otTer unforeseen opportunities to utilise the rich unexplored microbial world for increased utilization of plant biomass for energy. This research was aimed at .:reening for cellulosomal genes in an array of environmental metagenomes. In the study two environmental metagenomes were considered, the termite and the locust gut. Four cellulolytic bacterial strains were isolated from a lower termite (Coptotermes curvignathus) and the desert locust (Schistocerca gregoria). The bacterial isolates were named as Strain I, Strain 2. Strain 3 and Strain 4. Strain I and Strain 2 were isolated from locust gut while Strain 3 and Strain 4 were isolated from termite gut. The isolates were found to belong to Bacillus pumi/us (Strain I and Strain 2), Bacillus cereus (Strain 3) and Pseudumunas pulida (Strain 4) as confirmed by 16s rDNA sequence homology. These isolates were screened for the presence ofcellulosome genes by dot blot and southern blot hybridization using DNA probes designed from cohesin and dockerin domains ; the principal subunits of the cellulosome complex, where positive signatureS were detected in all isolates. Cellulnsnme gen’ were also screened by peR using primers designed from cohesin and dockerin domains of Clostridium thermacellum. The pCR products were sequenced, and the deduced sequences used for PhylogenetiC analysis. Most of the amplified sequences clustered with cohesin and dockerin containing sequences indicating the presence of these modules in the isolates. Results obtained in this research indicated that termites and locusts guts offer a potential source of cellulosome producing bacteria. More research is therefore required to isolate and screen the two metagenomes for cellulolytic and cellulosome producing bacteria. The isolation of bacteria from these insects may be useful in the degradation of cellulosic material.

Présentation

Page publiée le 17 novembre 2013, mise à jour le 9 mars 2018