A research team proposes Neisseriaceae oral bacteria as new model organisms that could aid in identifying new antimicrobial targets. They discussed the evolution of these caterpillar-like bacteria from a rod-shaped ancestor and their division mode.
Silvia Bulgheresi, an environmental cell biologist from the University of Vienna, and Frédéric Veyrier, a microbiologist from the Institut national de la recherche Scientifique, co-led the research team (INRS). Their new insights were published in Nature Communications.
What Is Neisseriaceae?
According to Science Direct, the family Neisseriaceae includes the genus Neisseria and several other genera. Neisseria genus members are typically gram-negative cocci.
On the other hand, Merriam-Webster defines it as a small family of nonmotile spherical gram-negative bacteria that are obligate parasites of warm-blooded vertebrates.
Neisseriaceae Bacteria Evolution
Despite the fact that our mouth contains over 700 species of bacteria and microbiota as diverse as that of our gut, little is known about how oral bacteria grow and divide. Bacteria find it difficult to survive in the mouth. The epithelial cells lining the inner surface of the oral cavity are constantly shed, and organisms that inhabit this surface will therefore compete for attachment with the salivary flow.
To better adhere to our mouths, bacteria in the Neisseriaceae family may have evolved a new way to multiply. Unlike most rods, which split transversally and then separate, some commensal Neisseriaceae that live in our mouths attach to the substrate with their tips and divide longitudinally along their long axis.
Furthermore, after the cell division is complete, the cells remain attached to one another, forming caterpillar-like filaments. Some cells in the resulting filament also take on different shapes, possibly to perform specific functions for the filament as a whole. According to the researchers, multicellularity allows for cell cooperation, such as division of labor, and may thus aid bacteria in surviving nutritional stress. Bacteria have evolved to divide along their longitudinal axis without separating from one another to survive in the oral cavity.
Research Findings on Evolution of Neisseriaceae Family
The researchers first used electron microscopy to survey bacterial cell shapes across the Neisseriaceae family, including the two standard cell shapes (rod and coccus) and the caterpillar-like filaments. The researchers deduced that multicellular, longitudinally dividing bacteria evolved from rod-shaped, transversally dividing bacteria by comparing their cell shapes and genomes across the Neisseriaceae family.
Furthermore, they could identify which genes were most likely responsible for the unusual multiplication strategy. They then used fluorescence labeling techniques to visualize the progression of cell growth in multicellular bacteria before comparing their genetic make-up to classic rod-shaped species.
Finally, they attempted to replicate the evolution by introducing genetic changes. Although they were unable to force rod-shaped bacteria to become multicellular, genetic manipulation resulted in cells that were longer and thinner.
According to Veyrier, they hypothesized that during evolution, the cell shape changed due to a reworking of the elongation and division processes, possibly to better thrive in the oral cavity.
Medical Applications Using the Oral Bacteria
Aside from assisting researchers in understanding how cell shape evolved, multicellular Neisseriaceae may be useful in studying how bacteria learned to live attached to the surface of animals, which is the only place they have been discovered so far.
However, Philipp Weber, Ph.D., a student on Bulgheresi's team who also worked on the study, points out that broadening the cell biology field to include additional morphologies and symbiotic species is also important for expanding the pool of protein targets (e.g., antibiotic targets) for biopharmaceutical applications.
Sammy Nyongesa, a Ph.D. student on Veyrier's team at INRS, believes that an evolutionary approach, such as the one used here for the Neisseriaceae, can reveal previously unknown protein targets.
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