A Bacterium in a Bacterium?!

We all host a large number of bacteria, fungi, viruses, and protozoa's in our intestines. Many of these organisms are beneficial and help us to degrade food and supply us with various nutrients. Insects also have microbes living inside their guts. Insects that feed on the sap of plants (aphids, leafhoppers, and whiteflies) must have certain bacteria in their gut to breakdown the sap into nutrients that the insect can use. Without these gut dwelling (endosymbionts) bacteria these insects would die. These "endosymbionts" often live within specialized host cells and have been transmitted from mother to offspring.

These insects can have several different bacteria in their gut. Carol von Dohlen of Utah State University in Logan set out to study the two known bacteria in the citrus mealybug. She expected to find them side by side or in separate cells. However, when Von Dohlen and her student Shawn Kohler examined the mealybugs' so-called "symbiotic spheres," long assumed to be host structures that housed bacteria, they became stumped. They knew from other data that there were two bacteria in the symbiotic spheres however no matter how hard they looked they could only find one bacterium in those spheres.

Upon discussing their frustrating laboratory results with a colleague, William McManus, he asked, "What if the symbiotic spheres ARE bacteria?" This question helped von Dohlen and Kohler realize that the symbiotic sphere was not a host cell but rather a bacterial cell and that another bacterium was living inside it. This is the first time that a bacterium has been found living inside another bacterium.

How and why one bacterium is living inside this different bacterium is not yet known but it is truly amazing! If you think you know it all and start getting bored just look at the world around you and surprises are just around the corner.

For more information on this article that appeared in July 26th, 2001 issue of Nature click here.

Take Care and Think Microbiologically! For more microbiology articles go to Suite101:Microbiology.

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