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Alise Muok

This microscopic hitchhiker is a friend to both plants and humans

Soil bacteria called Streptomyces are the guardian angels of the microbial world: They produce antibiotics that humans depend on and protect plants from harmful microbes. But because neither the bacteria nor their spores can move themselves around, researchers have long puzzled over how they find the plants they protect.

Now scientists have discovered that the microbe’s dormant spores (brown) hitch rides on the whiplike appendages—flagella—of mobile soil microbes (blue) heading for plant roots. The journey is an essential part of Streptomyces’ life cycle, the researchers report this month in The ISME Journal: Multidisciplinary Journal of Microbial Ecology.   

Microscopic examinations revealed the spore surface is lined with rows of proteins called rodlins that may grab a passing flagellum—working much like Velcro. The researchers have seen the hitchhikers transported 10 centimeters—the limit of the size of the dish they were on. They think that in soil, the spores may travel even farther.

A few other species of bacteria and a fungus are known to catch rides on other microbes. But this is a first for spores, which are known to latch on to insects and other small animals to travel long distances. The team suspects hitchhiking is a common mode of transportation for nonmotile bacteria.

Still, not everyone gets a free ride. For the bacteria providing the transport, says one of the study’s authors, “it’s like a ball and chain around your ankle.”