Bacterial Diversity Patterns along Gradients of Primary Productivity in Freshwater Ecosystems

Stanford University, Stanford CA

Investigators

Abstract

"Bacterial diversity patterns along gradients of primary productivity in freshwater ecosystems" One of the most striking aspects of life is that it is distributed unevenly across the Earth. Some regions (such as lowland areas and the tropics) have a high diversity of plant and animal life; others (such as mountain tops and the polar regions) appear nearly devoid of life. Differences in available environmental energy are a major cause of such patterns. However, it is unknown whether the diversity of the largest group of organisms on Earth (microorganisms) also varies with available energy. Preliminary observations suggest that a relationship may exist between bacterial diversity and available environmental energy in aquatic ecosystems. The goal of this project is to verify these preliminary observations. More specifically, bacterial diversity will be estimated in ponds that differ in available energy. Because most bacteria from environmental samples cannot be grown in the laboratory, bacterial diversity will be assessed using molecular techniques that do not require bacterial growth under laboratory conditions. Bacterial diversity will be estimated by extracting bacterial ribosomal genes from pond samples and sequencing these genes. Bacterial taxonomic diversity will be estimated from the sequence diversity of these genes. The diversity within a single bacterial functional group also will be estimated by extracting and sequencing amoA genes from pond samples. The amoA gene is unique to bacteria that oxidize ammonia. The diversity of these bacteria will be estimated from the sequence diversity of these genes. This study will be the first comprehensive attempt to measure bacterial diversity along a gradient of available energy. It has the potential to generate fundamental new knowledge concerning the distribution of microorganisms and could impact fields as diverse as environmental management and the search for novel pharmaceuticals.