P. J. Jansen van Rensburg

Phospholipid fatty acid profiling of microbial communities: a review of interpretations and recent applications

Profiling of microbial communities in environmental samples often utilizes phospholipid fatty acid (PLFA) analysis. This method has been used for more than 35 years and is still popular as a means to characterize microbial communities in a diverse range of environmental matrices. This review examines the various recent applications of PLFA analysis in environmental studies with specific reference to the interpretation of the PLFA results. It is evident that interpretations of PLFA results do not always correlate between different investigations. These discrepancies in interpretation and their subsequent applications to environmental studies are discussed. However, in spite of limitations to the manner in which PLFA data are applied, the approach remains one with great potential for improving our understanding of the relationship between microbial populations and the environment. This review highlights the caveats and provides suggestions towards the practicable application of PLFA data interpretation.

Microbial signature lipid biomarker analysis – an approach that is still preferred, even amid various method modifications

The lipid composition of microbial communities can indicate their response to changes in the surrounding environment induced by anthropogenic practices, chemical contamination or climatic conditions. A considerable number of analytical techniques exist for the examination of microbial lipids. This article reviews a selection of methods available for environmental samples as applied for lipid extraction, fractionation, derivatization and quantification. The discussion focuses on the origin of the standard methods, the different modified versions developed for investigation of microbial lipids, as well as the advantages and limitations of each. Current modifications to standard methods show a number of improvements for each of the different steps associated with analysis. The advantages and disadvantages of lipid analysis compared to other popular techniques are clarified. Accordingly, the preferential utilization of signature lipid biomarker analysis in current research is considered. It is clear from recent literature that this technique stays relevant – mainly for the variety of microbial properties that can be determined in a single analysis.

Microbial community function and structure on coal mine discard under rehabilitation

The rehabilitation of coal mine discard is problematic, especially since the lack of measures to evaluate the success of rehabilitation in terms of the self-sustainability of soil ecosystems established on these sites. In this study, the potential for using microbial community function and structure as such a measure was investigated using enzymatic assays (dehydrogenase, ß-glucosidase, urease and acid and alkaline phosphatase) and signature lipid biomarkers (PLFAs). Samples from seven coal discard sites in South Africa currently under rehabilitation, were investigated and the relationship between soil properties, vegetation cover and microbial properties analysed using PCA and RDA ordination techniques. Although the discard sites had different rehabilitation ages (one to eight years), no statistically significant differences existed between these sites based on physical and chemical characteristics. Differentiation was possible based on enzymatic activities and PLFA profiles. Sites with relatively higher vegetation cover and organic carbon content had a positive association with enzymatic activities and microbial biomass. Organic carbon content correlated significantly with ß-glucosidase (r = 0.80, P<0.05), urease (r = 0.96, P<0.05), acid phosphatase (r = 0.76, P<0.05), dehydrogenase (r = 0.69, P<0.10) and microbial biomass (r = 0.73, P<0.10). The characterisation of microbial community function and structure holds potential for evaluating rehabilitation progress on mine discard sites.