Bacterial endospores – shuttles to and from the deep biosphere? - NERC GW4+ DTP project

This project is one of a number that are in competition for funding from the NERC GW4+ DTP. The GW4+ DTP consists of the Great Western Four alliance of the University of Bath, University of Bristol, Cardiff University and the University of Exeter plus six Research Organisation partners. The partnership aims to provide a broad training in earth and environmental sciences, designed to train tomorrow’s leaders in earth and environmental science. For further details about the programme, please see http://nercgw4plus.ac.uk/.

Background

Bacterial spores are the most robust cell types known, some of which are able to survive even triple autoclaving and others possessing extreme longevity of millions of years (e.g. viable spores have been extracted from 25 Ma year old amber). Consequently, spores can accumulate in the environment, and it has been estimated that 100,000,000 thermophilic spores alone are deposited per square metre of sea floor per year.

However, the ecological significance of these large numbers of sedimentary spores is not understood. Are they all viable and able to germinate, where do they come from and are they included in deep biosphere cell estimates.

The ability of endospores to withstand high temperatures and the absence of an active metabolism may allow them to survive deep burial and to germinate in warmer, deeper layers, and/or to be transported in deep crustal and geothermal fluids.

Project aims and methods

Although spores are accumulating in the environment, their environmental significance is not understood. This project will investigate

- the viability of sedimentary spores and estimate half-life times
- the varying responses of a spore population to environmental parameters, including germination temperatures and pressures
- spore activation with deep geothermal substrates
- whether spores are included in deep biosphere cell estimates
- the longevity and distribution of spores that survive autoclaving. This includes estimating their depth in sediments
- whether buried thermophilic spores become active if reaching layers allowing the bacteria to germinate and grow, creating a spore cycle connecting the deep and surface environments.

The viability of spore populations will be investigated using viable counts (most-probable-number series) and germination experiments analysing the release of dipicolinic acid (DPA) by germinating spores. DPA will be analysed by high-pressure liquid chromatography. Viable counts will also be used as a source for isolation of spore-forming bacteria (e.g. those surviving autoclaving). Pure cultures and enrichments will be investigated using high-pressure and high temperature cultivation equipment. Molecular biological techniques will be used for identification of microorganisms in pure and enrichment cultures based (16S rRNA and functional genes).

Candidate

Any student with a background in microbiology or organic geochemistry will be suitable.

Training

You will receive training in aerobic and anaerobic microbiology, including enrichment, isolation and characterization of microorganisms, and viable count estimates (most-probable-number series).

Pure cultures and enrichments will be investigated using high-pressure and high temperature cultivation equipment. Metabolic investigations will involve analysis by high-pressure liquid chromatography, gas chromatography, light and fluorescence microscopy and spectrophotometry.

Molecular techniques will be used for identification of microorganisms in pure and enrichment cultures based (16S rRNA and functional genes). Geochemical analysis will include physical separation of spores from sediments for analysis and the extraction of spore biomarkers using different extraction techniques and analysis by HPLC.