All ETDs from UAB

Advisory Committee Chair

Asim K Bej

Advisory Committee Members

Robert W Thacker

Thane Wibbels

Jason Linville

Casey D Morrow

Document Type

Dissertation

Date of Award

2018

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

The perennially ice-covered lakes of the Antarctic continent are considered to be the ideal extreme ecosystems to study growth, sustenance, and evolution of microbial mats without any direct influence by higher organisms and other external environmental factors. This dissertation research utilized Next Generation Sequencing (NGS) technology and bioinformatics tools to study the microbial composition and metabolic potential of the microbial mats in permanently ice-covered freshwater Lake Untersee, Lake Obersee and their surrounding ecosystems in East Antarctica. Overall, the microbial communities in the microbial mats of Lake Untersee were distinct in regard to their compositions, shared taxa and metabolic potential as compared to those in their surrounding waters. Microbiologically, the large conical mats, found only in Lake Untersee, differed from the pinnacle and flat mats by having a higher abundance of Cyanobacteria, particularly Phormidium. Further investigation of the top three laminae of these conical mats revealed high abundances of Phormidium, Leptolyngbya, and Pseudanabaena in the top lamina, whereas the middle and the inner laminae had high abundances of heterotrophic bacteria. Unlike Lake Untersee, the mats in Lake Obersee showed high abundances of genes associated with heterotrophic bacterial activities. Furthermore, distinct microbial communities were found in the lithobiont communities collected from Lake Untersee and Lake Obersee shorelines above the ice-sheet. Predicted functional attributes of these microbial communities showed genes necessary for survival in nutritionally poor environments and high solar UV radiation. In addition, comparison of cold-adaptation and general cold-associated stress genes in the microbial community metagenomes of Lake Untersee with other Antarctic lake and soil metagenomes revealed that a common trend of the distribution of these genetic traits across all Antarctic metagenomes. The whole genome sequencing of pure cultures of Janthinobacterium sp. and Hymenobacter sp. from the freshwater lakes in the Schirmacher Oasis, located approximately 56 miles northwest of Lake Untersee, showed similar cold adaptation mechanisms as found in the microbial communities in the Untersee Oases. This study provides comprehensive information on the microbial community compositions, and metabolic potential needed to survive and propagate in the Antarctic freshwater ecosystems.

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