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  • As we walk through our daily environments,

  • we're surrounded by exotic creatures

  • that are too small to see with the naked eye.

  • We usually imagine these microscopic organisms, or microbes,

  • as asocial cells that float around by themselves.

  • But in reality, microbes gather by the millions

  • to form vast communities known as biofilms.

  • Natural biofilms are like miniature jungles

  • filled with many kinds of microbes from across the web of life.

  • Bacteria and archaea mingle with other microbes

  • like algae, fungi, and protozoa,

  • forming dense, organized structures that grow on almost any surface.

  • When you pad across a river bottom,

  • touch the rind of an aged cheese,

  • tend your garden soil,

  • or brush your teeth,

  • you're coming into contact with these invisible ecosystems.

  • To see how biofilms come about,

  • let's watch one as it develops on a submerged river rock.

  • This type of biofilm might begin with a few bacteria

  • swimming through their liquid environment.

  • The cells use rotating flagella to propel towards the surface of the rock,

  • which they attach to with the help of sticky appendages.

  • Then, they start producing an extracellular matrix

  • that holds them together as they divide and reproduce.

  • Before long, microcolonies arise,

  • clusters of cells sheathed in this slimy, glue-like material.

  • Microcolonies grow to become towers,

  • while water channels flow around them,

  • functioning like a basic circulatory system.

  • But why do microbes build such complex communities

  • when they could live alone?

  • For one thing, microbes living in a biofilm

  • are rooted in a relatively stable microenvironment

  • where they may have access to a nutrient source.

  • There's also safety in numbers.

  • Out in the deep, dark wilderness of the microbial world,

  • isolated microbes face serious risks.

  • Predators want to eat them,

  • immune systems seek to destroy them,

  • and there are physical dangers, too,

  • like running out of water and drying up.

  • However, in a biofilm, the extracellular matrix

  • shields microbes from external threats.

  • Biofilms also enable interactions between individual cells.

  • When microbes are packed against each other in close proximity,

  • they can communicate,

  • exchange genetic information,

  • and engage in cooperative and competitive social behaviors.

  • Take the soil in your garden,

  • home to thousands of bacterial species.

  • As one species colonizes a plant root,

  • its individual cells might differentiate into various subpopulations,

  • each carrying out a specific task.

  • Matrix producers pump out the extracellular goo,

  • swimmers assemble flagella and are free to move about or migrate,

  • and spore-formers produce dormant, tough endospores

  • that survive starvation,

  • temperature extremes,

  • and harmful radiation.

  • This phenomenon is called division of labor.

  • Ultimately, it gives rise to a sophisticated system of cooperation

  • that's somewhat like a multicellular organism in itself.

  • But because biofilms often contain many different microbes

  • that aren't closely related to each other,

  • interactions can also be competitive.

  • Bacteria launch vicious attacks on their competitors

  • by secreting chemicals into the environment,

  • or by deploying molecular spears to inject nearby cells with toxins

  • that literally blow them up.

  • In the end, competition is all about resources.

  • If one species eliminates another,

  • it keeps more space and food for itself.

  • Although this dramatic life cycle occurs beyond the limits of our vision,

  • microbial communities provide humans and other species with tangible,

  • and sometimes even delicious, benefits.

  • Microbes make up a major fraction of the biomass on Earth

  • and play a critical role within the global ecosystem

  • that supports all larger organisms,

  • including us.

  • They produce much of the oxygen we breath,

  • and are recruited to clean up environmental pollution, like oil spills,

  • or to treat our waste water.

  • Not to mention, biofilms are normal and flavor enhancing parts

  • of many of the foods we enjoy,

  • including cheese,

  • salami,

  • and kombucha.

  • So the next time you brush your teeth,

  • bite into that cheese rind,

  • sift through garden soil,

  • or skip a river stone,

  • look as close as you can.

  • Imagine the microbial jungles all around you

  • waiting to be discovered and explored.

As we walk through our daily environments,

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B2 TED-Ed microbial extracellular matrix bacteria soil

【TED-Ed】The microbial jungles all over the place (and you) - Scott Chimileski and Roberto Kolter

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    小爸 posted on 2017/07/18
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