Browsing by Author "Akeju, Tolutope O."

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    Biodegradation of Starch by Microbial Communities in Soil Collected from Olduvai Gorge in Northern Tanzania
    (2020-07-07) Akeju, Tolutope O.; Dunfield, Peter; Mercader, Julio; Dunfield, Peter; Mercader, Julio; Hynes, Michael; Snowdon, Lloyd; Samuel, Marcus
    Starch is the main component of most dietary intake by humans and it is synthesized as starch granules in different plant parts. Once exposed to the soil, starch is susceptible to biodegradation by enzymes produced by communities of soil bacteria and fungi. However, the preservation of starch granules in the archaeological record (thousands of years) has been documented. This preservation is poorly understood and there is a paucity of information in the scientific literature on the effects of oxygen and moisture on the enzymatic degradation of starches from different botanical sources in the soil. This study attempts to fill these knowledge gaps by examining soil–starch microcosms subjected to different moisture and oxygen conditions. These microcosms were sampled at regular intervals to observe the metabolic activity of the soil microbes using gas chromatography and also to identify the dominant microbial clades degrading the starch granules using 16S rRNA and 18S rRNA gene analyses. Commercial wheat, corn and potato starches were used in addition to a starch of ethnobotanical interest named Ipomoea longituba collected from Oldupai Gorge. Results indicated that wheat starch and Ipomoea longituba were the most susceptible to microbial degradation while potato starch was more recalcitrant. Starch degradation rates were significantly affected by starch type, soil moisture content, oxygen and calcium phosphate. 16S and 18S rRNA gene analyses showed that starch degradation involves both bacteria and fungi and important taxa that were involved in starch breakdown include Ascomycota, Alkalibacterium, Streptomyces and others, mostly Gram-positive bacteria. In addition, from the preliminary results on the microbial communities living in the rhizosphere of Ipomoea longituba and bulk soil, we can conclude that the microbiome of the rhizosphere of Ipomoea longituba is very different from the microbiome of the surrounding bulk soil that was collected from around 1 m2 of the plant.