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Activity Number: 511
Type: Invited
Date/Time: Wednesday, August 3, 2016 : 10:30 AM to 12:20 PM
Sponsor: Biometrics Section
Abstract #318299 View Presentation
Title: Analysis of Composition of Microbiome with Structural Zeros (ANCOMSZ)
Author(s): Abhishek Kaul and Siddhartha Mandal and Shyamal Peddada*
Companies: National Institute of Environmental Health Sciences and Public Health Foundation of India and National Institute of Environmental Health Sciences
Keywords: ANCOM ; Compositional Data ; Log-Ratios ; Microbiome ; Simplex ; Zero Counts

There is considerable interest among researchers to understand the effects of microbiome on various health outcomes. For a given specimen (e.g. fecal sample) obtained from an ecosystem (e.g. gut), one obtains the abundance of operational taxonomic units (OTUs) which are microbial genomic sequences clustered by sequence similarity. Using these OTU counts one can estimate the relative abundance of a taxon in the ecosystem but not the actual abundance in the ecosystem. Since sum of the relative abundances is 1, these data are constrained by a simplex. Since not all taxa are present in every ecosystem, it is a common to observe zero counts. For example, a 4-day old baby will not have Faecalibacterium, which is typically seen in the guts of babies who eat solid food. Thus the zero counts are due to biology and not due to low sequencing depth. In this talk we describe a general methodology that extends ANCOM (Mandal et al., 2015) to allow for structural zeros in the OTU count data. The proposed methodology can be used for not only comparing taxa abundance in two or more populations while adjusting for covariates, but also to describe networks among taxa.

Authors who are presenting talks have a * after their name.

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