Date of Award

Winter 2020

Project Type


Program or Major


Degree Name

Master of Science

First Advisor

Louis S Tisa

Second Advisor

Julia G Bryce

Third Advisor

Cheryl P Andam


The Geodermatophilaceae genera—Geodermatophilus, Blastococcus, and Modestobacter—live on rock surfaces and create biofilms that deteriorate stone architecture and monuments. Their biofilms increase the rate of weathering and erosion but are not well studied. Recently, thirteen strains were isolated, and their genomes sequenced. These new Geodermatophilaceae isolates along with Modestobacter marinus strain BC501 and Blastococcus saxobsidens strain DD2 were used in this study to evaluate biofilm formation under different environmental factors including temperature, light, and salt and heavy metal exposure. Ten isolates were used for experiments to recolonize back onto the rock substrates from which the isolates were obtained. For most of the isolates, optimal temperature was 28oC with light not influencing growth. These isolates exhibited salt tolerance and also showed elevated tolerance levels for heavy metals (cobalt, nickel, copper, lead, arsenate, and chromate). Two isolates—TF02A-26 and TF02A-35—were able to grow on the rock substrate after two months and one month, respectively in the absence of added nutrients. Determining how Geodermatophilaceae growth yields and biofilm adhesions are affected and effected by rock substrates could help preserve important stone structures from biodeterioration and help salty and heavy metal contaminated sites by bioremediation.