Microbial Swarms

We often envision microbes, particularly bacteria, as simple, solitary entities that meander aimlessly. However, these microorganisms demonstrate remarkable cooperation. Much like honeybees migrating to new hives, bacteria aggregate into colonies known as swarms, seeking a stable environment. This collective behavior underscores the adage that there is strength in numbers.

The formation of swarms enhances the density of bacterial cells, enabling them to better withstand antibiotic challenges—a subject of keen interest to microbiologists such as Souvik Bhattacharyya from the University of Texas at Austin. After observing E. coli engaging in unusual colony formations, Bhattacharyya isolated individual cells to assess their behavior and discovered that it was influenced by their past experiences. Bacteria originating from previously swarmed colonies exhibited a greater tendency to swarm again compared to those from non-swarming colonies.

Even more astonishing is that this behavior persisted in their descendants for at least four generations—approximately two hours. This revelation prompted Bhattacharyya and his research team to delve deeper into the reasons behind this phenomenon.

Microbial Memory

The idea of memory in microbes may initially appear odd given their lack of brains. However, this suggests that their memory mechanisms function quite differently from ours. According to Bhattacharyya, microbial memory resembles data stored on a computer. He elaborates:

“Bacteria may not have brains, but they can gather information from their surroundings, and through repeated encounters with certain conditions, they can retain that information for future use.”

In their recent study published in November 2023 in the Proceedings of the National Academy of Sciences (PNAS), the research team made genetic modifications to the E. coli genome, identifying two genes responsible for iron regulation and uptake. Iron, being the fourth most abundant element on Earth, plays a crucial role in cellular processes. Bhattacharyya explains:

“Long before oxygen populated the Earth’s atmosphere, primitive cellular life relied on iron for various functions. Iron is integral not only to the origin of life but also to its evolution, indicating that cells would utilize it in this manner.”

The researchers noted that bacterial cells with reduced iron concentrations were more inclined to swarm, suggesting that these swarms may be adept at locating environments with optimal iron levels. Conversely, cells with higher iron concentrations tended to form biofilms—dense, sticky communities of bacteria on solid surfaces. While swarms represent bacterial groups in transit, biofilms can be likened to bacterial cities. Additionally, the study found that these iron-based memories lasted for at least four generations before fading by the seventh.

The researchers hypothesize that lower iron levels activate bacterial memories, prompting microbes to swarm in search of iron-rich environments. In contrast, higher iron levels suggest a favorable environment, encouraging bacteria to remain and proliferate through biofilm formation.

A Shift in Perspective

Isn't it astounding that we live in an era where scientists are uncovering such remarkable truths about some of the smallest organisms on the planet? The discovery that even the tiniest life forms possess some form of memory is truly extraordinary.

If these minuscule entities can retain memories—however primitive—could it imply that they also possess a degree of consciousness? Some studies propose this might be the case, aligning with the theory of panpsychism.

Regardless, the transmission of these memories across generations serves as a poignant reminder of our shared experiences. In 2022, we learned that generational trauma and healing could also be inherited through epigenetics. If both microscopic organisms and humans can pass down memories or experiences, what about other animal species? How widespread is this intriguing phenomenon?

Dr. Oded Rechavi: Genes & the Inheritance of Memories Across Generations

In this podcast, Dr. Oded Rechavi discusses the genetic underpinnings of memory inheritance across generations, shedding light on how these processes might function in various organisms.

The Biology of Heritable Memories | Oded Rechavi | TEDxVienna

Oded Rechavi presents compelling insights into the biology behind heritable memories, exploring the implications of these findings for our understanding of memory in living organisms.

This article was initially published in the author's free newsletter, Curious Adventure, and was subsequently edited and republished on Medium with her permission. Thank you for your readership; it is greatly valued.