Solved: A Mangrovial Microbial Mystery


Breaking down the microbiology world one bite at a time

Solved: A Mangrovial Microbial Mystery

Once upon a time, in the dark humidity of Guadeloupe, there lived a magnificent creature. For millennia, it lived out a secret, peaceful life on the drenched leaves of red mangroves. Until, one day, suddenly, every microbiologist knew its name. Scientists, in awe of their magnificence, named these critters Thiomargarita magnifica. Thrust into the spotlight, T. magnifica are now the largest known bacteria in the world! Going against the very grain of what we know microbiology to be, these organisms are not microscopic.

While scouring the shallow tropical marine environment of Guadeloupe, a team of scientists came across this microbe (macrobe?) and characterized it as the largest bacterium known with a surprisingly complicated organization. These bacteria look like thin white strings, almost a centimeter long. They’re approximately the width of your fingernail!

Historically, bacteria have been considered the most primitive of organisms. In a world of multi-compartment, specialized-function purses, bacteria are thought to be tote bags, just holding all that keeps them alive in a single cavity. Our human cells in contrast are like hyper-specialized purses with unique compartments, called organelles, that carry out specific functions. For example, we have a nucleus, a membrane-bound organelle, that holds all our DNA in one place. Bacteria usually just keep their DNA somewhere within that tote bag, no specific location, just inside. So, when scientists put T. magnifica under the microscope to observe its DNA, what they did not expect was DNA wrapped up in a membrane-bound compartment. But that is what they found. These compartments looked like little pips in a watermelon, so the team decided to name them pepins. Pepins are reminiscent of a eukaryotic cell (like ours), with the DNA sequestered in a compartment. So perhaps, T. magnifica isn’t a simple tote bag after all. Could this bacterium be the key to understanding the evolution of purses from tote bags? Maybe. One thing is certain, T. magnifica is begging us to ask the question: how much do we not know?

Figure 1. Schematic of T. magnifica. This bacterium has a white string-like morphology. When looked at under the microscope, we can see a large central vacuole, organelle-like compartments, and pepins which are membrane-bound structures that store genomic material. Image created by author using Adobe Illustrator.

Link to the original post: Volland, J. M., Gonzalez-Rizzo, S., Gros, O., Tyml, T., Ivanova, N., Schulz, F., Goudeau, D., Elisabeth, N. H., Nath, N., Udwary, D., Malmstrom, R. R., Guidi-Rontani, C., Bolte-Kluge, S., Davies, K. M., Jean, M. R., Mansot, J. L., Mouncey, N. J., Angert, E. R., Woyke, T., & Date, S. V. (2022). A centimeter-long bacterium with DNA contained in metabolically active, membrane-bound organelles. Science (New York, N.Y.)376(6600), 1453–1458.

Featured image: Created by the author using Adobe Illustrator and Craiyon.