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Individual bacterial cells have short memories. But groups of bacteria can develop a collective memory that can increase their tolerance to stress. This has been demonstrated experimentally for the first time in a study by Eawag and ETH Zurich scientists published in PNAS.
Martin Ackermann comments: "If we understand this collective effect, it may improve our ability to control bacterial populations." The findings are relevant, for example, to our understanding of how pathogens can resist antibiotics, or how the performance of bacterial cultures in industrial processes or wastewater treatment plants can be maintained under dynamic conditions. After all, bacteria play a crucial role in almost all bio- and geochemical processes. From a human perspective, depending on the particular process, they are either beneficial -- e.g. if they break down pollutants or convert nutrients into energy -- or harmful, especially if they cause diseases. For the researchers, says Mathis, another important conclusion can be drawn: "If you want to understand the behavior and fate of microbial populations, it's sometimes necessary to analyze every single cell."
Decision making is not limited to animals like humans or birds. Bacteria also make decisions with intricate precision. Imagine being so tiny that you are literally moved by water molecules bumping into you. This is what bacteria encounter perpetually. Now, imagine having no eyes, no ears, no sense of touch, no taste or nose. How would you know what or who was around you? How would you find food now as compared to where you were a short time ago? This is where being able to sense important things like a food source is critical. Bacteria have this on their “mind” all the time. Depending on the size of a bacterium’s genome, these tiny organisms have the ability to sense hundreds to thousands of internal and external signals like carbon sources, nitrogen sources, and pH changes. If these bacteria are motile (able to move around), they can compare how conditions are for them now against how they were a few seconds ago. That’s right, bacteria have a memory albeit short. If conditions are better, they can continue to move in a forward direction. If conditions are worse compared to a few seconds earlier, they can change direction and continue searching for better conditions in their environment to generate energy. But, how do they decide?
Collective memory is the shared pool of knowledge and information in the memories of two or more members of a social group. The English phrase “collective memory” and the equivalent French phrase “la mémoire collective” appeared in the second-half of the nineteenth century. The philosopher and sociologist Maurice Halbwachs analyzed and advanced the concept of the collective memory in the book La mémoire collective (1950). Collective memory can be shared, passed on, and constructed, by large and small social groups. Examples of these groups could include a government or popular culture, among others.  Collective memory parallels the memory of a person who is better at recalling images than words; but also exhibits key differences and features, such as cross-cueing.
Even though all the cells of the human body share a common genomic blueprint, epigenetic activity such as DNA methylation, introduces molecular diversity that results in functionally and biologically different cellular constituents. In cancers, this ability of epigenetic activity to introduce molecular diversity is emerging as a powerful classifier of biological aggressiveness.
For billions of years, single-celled creatures had the planet to themselves, floating through the oceans in solitary bliss. Some microorganisms attempted multicellular arrangements, forming small sheets or filaments of cells. But these ventures hit dead ends. The single cell ruled the earth.
Then, more than 3 billion years after the appearance of microbes, life got more complicated. Cells organized themselves into new three-dimensional structures. They began to divide up the labor of life, so that some tissues were in charge of moving around, while others managed eating and digesting. They developed new ways for cells to communicate and share resources. These complex multicellular creatures were the first animals, and they were a major success. Soon afterward, roughly 540 million years ago, animal life erupted, diversifying into a kaleidoscope of forms in what’s known as the Cambrian explosion. Prototypes for every animal body plan rapidly emerged, from sea snails to starfish, from insects to crustaceans. Every animal that has lived since then has been a variation on one of the themes that emerged during this time.
How did life make this spectacular leap from unicellular simplicity to multicellular complexity? Nicole King has been fascinated by this question since she began her career in biology. Fossils don’t offer a clear answer: Molecular data indicate that the “Urmetazoan,” the ancestor of all animals, first emerged somewhere between 600 and 800 million years ago, but the first unambiguous fossils of animal bodies don’t show up until 580 million years ago. So King turned to choanoflagellates, microscopic aquatic creatures whose body type and genes place them right next to the base of the animal family tree. “Choanoflagellates are to my mind clearly the organism to look at if you’re looking at animal origins,” King said. In these organisms, which can live either as single cells or as multicellular colonies, she has found much of the molecular toolkit necessary to launch animal life. And to her surprise, she found that bacteria may have played a crucial role in ushering in this new era.
The choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals. Choanoflagellates are collared flagellates having a funnel shaped collar of interconnected microvilli at the base of a flagellum. They have a distinctive cell morphology characterized by an ovoid or spherical cell body 3–10 µm in diameter with a single apical flagellum surrounded by a collar of 30–40 microvilli (see figure). Movement of the flagellum creates water currents that can propel free-swimming choanoflagellates through the water column and trap bacteria and detritus against the collar of microvilli, where these foodstuffs are engulfed. This feeding provides a critical link within the global carbon cycle, linking trophic levels. In addition to their critical ecological roles, choanoflagellates are of particular interest to evolutionary biologists studying the origins of multicellularity in animals. As the closest living relatives of animals, choanoflagellates serve as a useful model for reconstructions of the last unicellular ancestor of animals.
Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom), but this classification is outdated. Archaeal cells have unique properties separating them from the other two domains of life, Bacteria and Eukaryota. The Archaea are further divided into multiple recognized phyla. Classification is difficult because the majority have not been studied in the laboratory and have only been detected by analysis of their nucleic acids in samples from their environment.
If you’ve ever tried to pick a location for dinner with a medium to large group of people, you know that group communication and decision making can be really hard.
So it may come as a surprise that many bacteria are actually quite good at this! And new research suggests that we might be able to disrupt that “group communication” in ways that could make agriculture safer without the use of traditional pesticides.
Bacteria, it turns out, emit signaling molecules to “convince” neighboring bacteria to express a gene, and when a sufficient density of these molecules is detected, a positive feedback loop kicks in that gets the laggards on board. This phenomenon, known as quorum sensing1, was first observed in bioluminescent bacteria 40 years ago2, but its importance and applications are still being explored.
Microbial intelligence (popularly known as bacterial intelligence) is the intelligence shown by microorganisms. The concept encompasses complex adaptive behavior shown by single cells, and altruistic and/or cooperative behavior in populations of like or unlike cells mediated by chemical signaling that induces physiological or behavioral changes in cells and influences colony structures.