| Complex relationships exist across all different scales — from the dance of the stars and galaxies in the universe, to Earth's ecosystems and societies, to the interactions of the microbes that occupy the microscopic world.
These minuscule organisms have pretty active social lives. They may not chat about the weather, throw parties or trade recipes, but that doesn't make them antisocial. Microbes exist pretty much everywhere: Thriving bacterial communities live in the plumbing in your house, in the cheese in your fridge, and in your ears, skin and gut. They are constantly interacting with one another — collaborating, fighting and coexisting within their microscopic kingdoms.
They exchange genetic material and nutrients. They form groups to defend themselves. They work together to perform biochemical reactions. Their interactions guide biology in critical ways, from maintaining a host's gut health and aiding digestion to churning out oxygen that other creatures breathe.
These communities take on different arrangements. Some are made up of one species; others are fantastically diverse. Some microbes form ensembles known as biofilms: thin layers of cells that cling to and spread across moist environments, such as soil or the human tongue. In all these situations, bacteria must communicate to work together, and they accomplish this feat in various ways. Hairlike structures made of protein, known as pili, connect bacterial cells to exchange DNA. Many species package molecules into little cellular bubbles known as vesicles, which they release into the environment for neighbors to pick up.
Understanding the dynamics and functions of microbial communities is a monumental task, since they are hidden in the invisibility of the microscale. Whether out in nature or in a petri dish, a community of microbes is not only a jungle of diversity — with countless species, subspecies and strains — but also constantly in flux. Powerful microscopy and genetic sequencing technologies are letting microbiologists get ever closer looks into how microbes mingle. The more researchers zoom in, the more it becomes clear that the microbial world is better connected than anyone realized.
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Some bacteria build bridges to share nutrients and resources. These so-called bacterial nanotubes, which are made of cell membrane, were first observed over a decade ago in the lab. Since then, further research has suggested that bacteria send cargo such as protein building blocks, enzymes and toxins across these bridges to one another. In a recent study, researchers discovered that in the ocean, bacterial nanotubes connect photosynthetic bacteria known as Prochlorococcus, which create 10% to 20% of the atmosphere's oxygen. The findings suggest that the world of bacteria may be more intricately connected, and across vaster distances, than anyone knew.
Unifying theories that describe how bacterial ecosystems assemble are largely lacking. According to one group of microbiologists, that's because most studies try to name the species found in them. A better way forward, they argue, is to organize the cells by their role in the community — specifically, their metabolism. "Taxonomy is not as informative as function," said Otto Cordero, a microbiologist at the Massachusetts Institute of Technology. The microbiologists hope to develop tools that can quickly predict a microbial community's function and how it might evolve.
Bacteria aren't the only microbes with active social lives. Sociovirologists, a self-named branch of virologists, have discovered that viruses cheat and cooperate — behaviors that you'd expect of humans, insects and even bacteria, but not of typically solo and simple viruses. The scientists theorize that viruses can cheat by replicating using proteins created by other viruses; they can also work together by sharing proteins. It's possible that one day sociovirologists will learn enough about viral social lives to weaponize these behaviors against them. | 
