Date of Award

2019

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Specialization

Environmental and Earth Sciences (EES)

Department

Geosciences

First Advisor

Dawn Cardace

Abstract

We present research observing and documenting the model organism, Pseudomonas fluorescens (P. fluorescens), building biofilm on a natural mineral substrate composed largely of bornite (Cu5FeS4), a copper-iron sulfide mineral, with closely intergrown regions of covellite (CuS) and chalcopyrite (CuFeS2). In examining biofilm establishment on sulfide minerals, we investigate a potential habitable niche for microorganisms in extraterrestrial sites. Geochemical microenvironments on Earth and in the lab can also serve as analogs for important extraterrestrial sites, such as sheltered, subsurface microenvironments on Mars. The sulfur cycle has been important to Mars’s surficial and interior processes during most of its geological record (King and McLennan, 2010; McLennan and Grotzinger, 2009). By growing P. fluorescens on polished chips of a sulfur-rich mineral (a Martian microenvironment analog material), we asked which distinct mineral phases bacteria selected as adhesion points. We collected cell count data, applied Raman spectroscopy, and tested FTIR spectroscopy as a complementary tool, to query whether biologically derived signals increase in intensity as bacteria grow in culture, and if the character of the mineral substrate controls cell distribution to some degree. Through use of the ANOVA statistical test on Raman peak intensity data, we found significant differences between the biologically derived signal intensity (i.e., bonds related to EPS, amide I, amide III) for minerals: amide presence on bornite differs from on other substrates. ANOVA tests of cell counts yielded no significant difference between mineral substrate. We report that bornite mineral surfaces are subtly preferred in early adhesion by this model biofilm former.

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