MICROBIAL COMMUNITY COMPOSITION OF A NATURAL SEDIMENT SALINITY GRADIENT: TAXONOMIC AND METABOLIC PATTERNS AND CONTROLLING FACTORS

Author: Thomas Charles Jeffries

Jeffries, Thomas Charles, 2012 MICROBIAL COMMUNITY COMPOSITION OF A NATURAL SEDIMENT SALINITY GRADIENT: TAXONOMIC AND METABOLIC PATTERNS AND CONTROLLING FACTORS, Flinders University, School of Biological Sciences

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Abstract

This thesis investigates the distribution of microbial taxonomy and metabolism along a continuous natural gradient of salinity and nutrient concentration, the Coorong lagoon, Australia. By applying Next-Generation DNA sequencing techniques, I use this system as a model to observe the relative influence of local habitat variability on sediment microbial community structure. I also use the Coorong as a reference point to determine global scale determinants of metagenomic patterns in microbial diversity. My data demonstrated strong shifts in the abundance of both bacterial and archaeal taxonomic groups along the gradient coupled to an overrepresentation of genes involved in halotolerance and photosynthesis in the most hypersaline samples relative to the marine salinity samples used as a baseline. Whilst these gradient driven shifts indicate the influence of salinity and nutrient content on microbial community structure, the overall genomic signature of the community remained conserved along the gradient. When this signature was compared to other metagenomes from a variety of habitats and salinities, Coorong samples were most similar to other sediment and soil habitats which formed a discrete ‘sediment’ cluster regardless of salinity variation. This indicates for the first time the fundamental role of substrate type in determining microbial community metabolism and highlights the hierarchical nature of variables acting on different scales of community organization.

Keywords: microbial ecology,salinity,metagenomics,microbial biogeography
Subject: Biological Sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2012
School: School of Biological Sciences
Supervisor: Dr. Jim Mitchell