Graduate Spotlight: Alecia Septer
Expected Graduation: Fall 2012
Degree Objective: Ph.D. in Microbiology
Other Degrees: B.S. in Microbiology
Alecia Septer, a microbiology doctoral candidate, studies how environmental factors affect bacterial communication and behavior. Environmental cues can stimulate many bacterial actions, including antibiotic production, DNA transfer or, as in Septer’s research, bioluminescence – the emission of light by living organisms.
Working with Dr. Eric Stabb, Septer focuses on a unique symbiosis between a luminescent bacterium, called Vibrio fischeri, and the Hawaiian bobtail squid.
“What drew me to this symbiosis was the thought of working on such a well-studied marine interaction that is relatively easy to study compared to other symbioses,” said Septer. “Also, the fact that the bacterial symbiont makes light is just amazing, and I really wanted to learn how they control light production.”
The host-microbe relationship begins immediately following the Hawaiian bobtail squid’s birth. As soon as it begins to swim, the bobtail squid attracts V. fischeri to a specialized light organ in its mantle. The bacteria glow after colonizing the light organ in large numbers.
At night, the squid’s glimmering body offsets its moonlit silhouette, protecting it from would-be predators lurking below. In return, the squid furnishes V. fischeri with a steady supply of sugars and amino acids for food.
In a laboratory setting, Septer analyzes the details underlying this relationship.
According to her, bacteria use chemical agents known as pheromones to communicate while colonizing a host species. As a bacterial colony grows, the accumulation of pheromones stimulates further changes in the bacteria.
“My research involves identifying the mechanisms of how certain environmental factors turn on pheromone production to control luminescence in V. fischeri, and determining these factors are important during the infection and colonization of the squid host,” she said.
So far, Septer has examined how the presence of oxygen and different growth conditions affect the bacterium’s pheromone production.
“Since there is a clear link between pheromone production and host colonization, determining when and how bacteria control pheromone production is important for us to understand how bacteria communicate during both disease and beneficial relationships with their hosts,” she said.
Septer and Dr. Stabb’s findings contribute to growing body of knowledge about how scientists could manipulate bacterial behavior.
“If we can identify the conditions that turn on or off pheromone production, it is possible to manipulate bacterial communication,” said Septer. “These changes could stop bacterial chatter to prevent virulence or turn on pheromone production to activate a beneficial trait of a bacterium.”
Septer says scientists have already genetically modified plants to disrupt the communication of specific pathogenic bacteria, allowing the plant to resist infection by disrupting the pathogen’s communication. Medical researchers can apply this approach to the treatment of human diseases with an improved understanding of how bacteria communicate during colonization.
“If researchers can understand enough about what controls bacterial communication, they might be able to stop the progression of an infection by using compounds or conditions that prevent production of the bacterial pheromones, which in many pathogens is required for causing disease,” said Septer.
After graduation, Septer plans to complete postdoctoral training and apply for research faculty positions to continue her studies on host-microbe relationships. She is particularly interested in studying Bacteroides fragilis, a common bacterium in the human intestine that produces eight types of carbohydrates.
One of these carbohydrates – called PSA – has beneficial effects on the human host’s immune system when confined to the intestine. However, PSA causes abscesses to form when it moves into the bloodstream or the abdominal cavity.
“There are all sorts of interesting questions to ask about this system,” said Septer. “For example, what controls PSA production? Why is it beneficial at one site but problematic at another?”
Eventually, Septer plans to direct her own research laboratory to delve further into complex host-microbe relationships.
“I am sure wherever I end up it will be intellectually engaging, which, ultimately, is what I am looking for.”
Story by Ben Benson; Photography by Alecia Septer