add correlation b-n microbes and metabolites assay and protocol

assays/CorrelationBetweenMicrobesAndMetabolites/protocols/CorrelationBetweenMicrobesAndMetabolitesProtocol.md

+## Correlation between microbes and metabolites
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+We calculated the correlation between every pair of microbes and metabolites to reveal the potential cross feeding between the microbe species. At each combination of plant lineages (WT / SWEET2 / SWEET4 / SWEET11,22) and root segments (2cm / 4cm / 6cm / whole root), we performed 16s RNA sequencing to quantify the abundance of different microbial classes and also mass spectrometry to measure the abundance of different metabolites.
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+For each pair of microbe class and metabolite, we calculated their spearman correlation across different plant lineages and root locations to construct the correlation matrix; matrix elements that correspond to p-value >0.05 are deemed insignificant and replaced with 0 (i.e., not connected in a complex network). We used the iGraph package of R to display this bipartite network (Csárdi, G. et al., 2023). Communities within this network are detected using the label propagation algorithm (Raghavan, U.N., 2007).
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+Reference ID: KRT64abe6afd69ae
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