(167 words)Sorghum is the second most cultivated crop in Africa and is a staple food source of many African communities. Exploiting the associated plant growth promoting bacteria (PGPB) has potential as an agricultural biotechnology strategy to enhance sorghum growth, yield and nutritional properties. Here we use Terminal-Restriction Fragment Length Polymorphism (T-RFLP) and Denaturing Gradient Gel Electrophoresis (DGGE) to evaluate the factors that potentially shape rhizospheric and endophytic bacterial communities associated with sorghum farmed in South Africa. Microbial diversity was typically higher in the rhizosphere and rhizoplane compared to the endophytic zones (root, shoot and stem). Geographical location was one of the main drivers in describing microbial community assemblages found in rhizospheric and endophytic sorghum-linked niches. NO 3 -N, total nitrogen and pH were clearly identified as the main abiotic factors shaping sorghum-associated soil communities.Our results also suggest that specific bacterial taxa with potential N-fixing capacities (Acetobacter sp., Azospirillum sp., Pantoea sp., Bacillus sp. and cyanobacteria) are consistently detected in sorghum-created rhizospheric and endophytic environments, irrespective of environmental factor effects.

Xerophyta humilis is a poikilochlorophyllous monocot resurrection plant used as a model to study vegetative desiccation tolerance. Dehydration imposes tension and ultimate loss of integrity of membranes in desiccation sensitive species. We investigated the predominant molecular species of glycerolipids present in root and leaf tissues, using multiple reaction monitoring mass spectrometry, and then analysed changes therein during dehydration and subsequent rehydration of whole plants. The presence of fatty acids with long carbon chains and with odd numbers of carbons were detected and confirmed by gas chromatography. Dehydration of both leaves and roots resulted in an increase in species containing polyunsaturated fatty acids and a decrease in disaturated species. Upon rehydration, lipid saturation was reversed, with this being initiated immediately upon watering in roots but only 12-24 hr later in leaves. Relative levels of species with short-chained odd-numbered saturated fatty acids decreased during dehydration and increased during rehydration, whereas the reverse trend was observed for long-chained fatty acids. X. humilis has a unique lipid composition, this report being one of the few to demonstrate the presence of odd-numbered fatty acids in plant phosphoglycerolipids.

No abstract