Booth Id:
MCRO032
Category:
Microbiology
Year:
2021
Finalist Names:
Nazareth, Michelle (School: Georgiana Bruce Kirby Prep School)
Abstract:
Bacteria are important in natural ecosystems, and motile bacteria use flagella to swim toward stimuli. To produce motility, a flux of protons drives flagellar rotation in a cell membrane-embedded motor. Natural magnetic fields are associated with magnetite, a common form of iron minerals. Magnetotactic bacteria contain magnetite nodules that align their motility with Earth’s magnetic field. This research investigated how bacteria evolved this ability. Motile, known soil bacteria swam through a 1.25T neodymium magnetic field into fresh LB medium. After overnight incubations, bacteria beyond the field were visualized by Gram staining and imaged at 1000X magnification. The magnetic field caused differential responses in the motile species’ composition when compared to control samples. Control samples contained both gram-positive and gram-negative bacteria while magnetic samples contained mostly gram-negative bacteria. Additionally, the mean magnetic bacterial count was statistically significantly less than the control bacteria at the α=.01 level. To confirm this effect, 16s rRNA analysis was performed and confirmed that different bacterial species were present in the sample groups. This effect has not been previously reported, and establishes that magnetic fields selectively filter the motility of mixed soil bacterial species, even without deposited magnetite nodules. The force acting on individual bacterium was calculated and the deceleration was sufficient to cause deviation due to the magnetic field. I propose the hypothesis that magnetic fields associated with magnetite minerals could have had a selective effect on populations of the first motile bacterial species which was later amplified as they evolved the ability to deposit intracellular magnetite nodules.