Latest Discoveries Highlight the Exquisite Molecular Arrangement of Simplest Life
Spring will soon be upon us. It’s the time of year when a young man’s fancy turns to love (or baseball, if he’s thinking clearly). For my wife, this is the season when she becomes passionate about cleaning out the garage.
Unfortunately, no one else seems to share her passion, but it doesn’t matter. Soon enough, the contents of our garage will populate the driveway. After sifting through furniture, clothing and assorted odds and ends, one-by-one, everything will go back into the garage in its proper place. Items that we use frequently will be stored in handy, easy-to-reach locations. The stuff we seldom use will be tucked away in an out-of-the-way corner. And, of course, there is the pile for Goodwill.
Organization evinces the work of an intelligent agent. Arranging a space for functional utility requires foresight and planning. As recent advances attest, this type of organization defines the simplest life-forms: bacteria.
Microbiologists didn’t always think so. Prior to the mid 1990s, microbiologists held a view of bacteria as “vessels” that contained a jumbled assortment of life molecules randomly dispersed inside the cell. In short, researchers did not suppose that these organisms possessed any type of internal organization.
This perception of bacteria stood in sharp contrast to the remarkable internal organization displayed by the complex cells (eukaryotes) that make up the multicellular fungi, plant, and animal kingdoms, as well as the single-celled protozoans. Each eukaryotic cell possesses numerous internal compartments, membrane systems, a nucleus, organelles, a cytoskeleton, and other components that organize the cell contents at the subcellular, and even molecular, level.
The historical view of bacteria is changing, however. Microbiologists now recognize that these microbes display a remarkable degree of internal organization, although it doesn’t involve subcellular structures. Rather, the organization occurs at the molecular level—both spatially and temporally. An article appearing in Nature describes recent work on proteins that form cytoskeletal systems in bacteria, illustrating the brilliant organization of the bacteria’s interior.
Traditionally, microbiologists thought that bacteria lacked a cytoskeleton. In fact, the absence of a cytoskeleton was considered a defining feature of bacterial cells, one that presumably distinguishes them from eukaryotic cells. According to tradition, only complex eukaryotic cells possess a cytoskeleton.
The article highlights several cytoskeletal proteins within bacteria, including FtsZ, MreB, Crescentin, and MamK. Multiple copies of FtsZ accumulate at the middle of the cell and aggregate to form a ring that extends around the inner surface of the cell wall. During cell division, the FtsZ ring contracts to pinch the mother cell into two daughters. This ring is properly understood as a cytoskeletal component. The MreB protein forms a helical structure that spans the length of nonspherical bacterial species. The MreB complex helps establish cell shape and serves as a “track” to ferry molecules around inside the bacterial cell. New work also reveals that bacteria employ an intricate mechanism to insure that the MreB complex properly segregates between daughter cells during replication. Crescentin also plays a role in determining cell shape. MamK forms a track-like structure inside magnetotactic bacteria that orients magnetic iron ore crystals housed within structures called magnetosomes. These structures help the bacteria to sense the Earth’s magnetic field.
Common experience teaches that it takes thought and intentional effort to carefully organize a space for functional use. By analogy, the surprising internal organization of bacteria bespeaks intelligent design. Instead of resembling my garage prior to spring cleaning, the interior of the simplest cell is best described as a space that has been carefully organized to efficiently carry out life’s most basic processes. Disrupting this organization, in many cases, is lethal.
For more information on the exquisite organization of living systems and what it means for the RTB and the evolutionary models for the origin of life, see the book I coauthored with Hugh Ross, Origins of Life or my new book, The Cell’s Design.