Application of the Gini coefficient for assessment of microbial communities` diversity in soil treated with biofertilizer

Abstract

Metabolic activity and structure of microbial communities are important indicators for soil health and fertility. BIOLOG`s Ecoplate patented technology provides a method for estimating soil microbial community structure based on different substrate utilization. The optical density (OD) in the wells changed during the plate incubation due to the reduction of the tetrazolium dye and the OD values are used for the calculation of different indexes as parameters for microbial activity and community structure. The Gini coefficient, which was originally employed by economists for the estimation of wealth and income, has applications in a variety of biological studies. The Gini coefficient, alone or in combination with other indexes, can be used for the assessment of microbial diversity and species evenness. The aim of the current study was to calculate the Gini coefficient at several consecutive time points during the EcoPlate incubation, to make a graphical presentation through the corresponding Lorenz curves and to estimate the effect of applied biofertilizer on the soil microbial diversity. The results showed that the Gini coefficient decreased with the EcoPlate incubation and in case of a small difference between estimated coefficients, the graph was not very representative. The clear visual distinction between the corresponding Lorenz curves was not achievable. The Gini coefficient can be a useful parameter for estimating microbial diversity with a proper choice of time point measurement. Additional computations, which involve other indexes, comparisons or correlation analysis between them, can increase the benefits of the Gini coefficient application in the EcoPlate technique.

Keywords

• microbial communities
• metabolic activity
• biolog ecoplate technique
• the gini coefficient
• lorenz curve