A Study on Fractal Morphogenesis in Bacteria as a Response to Environmental Stress

UNCP Author/Contributor (non-UNCP co-authors, if there are any, appear on document)
Hannah E. Woriax (Creator)
The University of North Carolina at Pembroke (UNCP )
Web Site: http://www.uncp.edu/academics/library
Marilu Santos

Abstract: Bacteria respond to the biochemical and physiochemical stimuli within their environment by formation of fractal colonies. This phenomenon has been studied and is thought to be the result of chemical signaling between single cells, as well as activation or deactivation of genes and even conjugation. This study was performed to demonstrate fractal morphogenesis in Escherichia coli, a gram negative bacterium, and Micrococcus luteus, a gram positive bacterium, as a response to herbal mixtures and diffusion-limited agar. Actively growing Micrococcus luteus and Escherichia coli were surface plated on standard 12% LB agar, 8% LB agar, 17% LB agar, standard agar + garlic, standard agar + golden seal, standard agar + sage, and differential media eosin methylene blue agar, selective for E. coli, and mannitol salt agar, selective for M. luteus, for 24 to 48 hours at 37?C and 25?C, respectively. Non-fractal colony growth ranged in size from 0.1-1.0mm and fractal colony growth ranged from 3.0-7.5mm in size. All herbs tested: goldenseal, garlic, and sage, proved to encourage fractal growth in hard and soft agar with hard agar being the more promising fractal growth medium. Therefore, hard agar limits the amount of nutrient diffused throughout the agar, promoting fractal growth and development. On all media tested the death rate for bacterium with garlic administered was 50% for M. luteus and 100% for E. coli at 24 hrs. Sage and goldenseal had far less of an effect, with bacterial death rate on all media not overcoming 50% for either E. coli or M. luteus using sage and goldenseal at 24 hrs and 48 hrs, respectively. Colonies surviving displayed fractal growth as well as non-fractal growth. The fractal colonies formed were tested for their viability which showed them remaining viable up to 30 days without refrigeration. These results indicate that bacterial fractal growth and development was promoted as an adaptive response to the use of retardant nutrient dispersal agar and the presence of herbal tinctures as unusual and irregular environment situations.

Additional Information

Honors Project
Language: English
Date: 2009
Fractal Morphogenesis, Bacteria, Microbiology, Environmental Stress