Microbe Spotlight: Week 8

NDSU Microbiology
by NDSU Microbiology

The students in Infectious Disease Pathogenesis Lab blogged about the strange and wonderful this semester. This week's guest bloggers are: Matt Carlson and Lacey Weaver. This is the last spotlight for the semester, so thanks for reading!

The Arnold Schwarzenegger of the Microbe World

Deinococcus radiodurans is a Gram-positive bacterium that begins life as a diplococci, but grows to form tetracocci upon full maturation. This non-pathogenic, obligate aerobe is usually found in soil and fecal matter, although the microbe’s natural habitat is unknown.

It holds the Guinness Book of World Records record for the world’s toughest bacterium. Also known as Conan the Bacterium, D. radiodurans is capable of surviving five times the radiation required to sterilize a culture of E. coli, oxidation, cold temperatures, a vacuum, dehydration, acid, and UV light. It is thought that one of the main reasons D. radiodurans is able to survive such a wide array of hazards is that it carries between four and 10 copies of its genome stacked one on top of another, whereas most bacteria only have a single copy.

These extra copies serve as backups to each other—in the event one copy is damaged, there will almost always be another copy somewhere that still contains the correct gene sequences. Scientists believed this evolved originally as a means of dehydration resistance, although the specific mechanism is unknown as there are no unique repair mechanisms in Deinococcus radioduarns that aren’t found in other bacteria.

Current uses for D. radiodurans include radioactive waste site cleanup, and research is being done to see if it could be used as a “vaccine” for gamma-radiation patients.

By Matt Carlson

Image Source: Environmental Molecular Sciences Laboratory (EMSL); Licence

Xenorhabdus nematophila

Xenorhabdus nematophila is a Gram-negative, peritrichous bacterium that lives in soil. X. nematophila was first discovered by Gerard Thomas and George Poinar in 1966. X. nematophila is pathogenic to insects and lives in a symbiotic relationship in the gut of the infective juvenile of the nematode, Steinernema carpocapsae. This relationship is mutualistic as the bacteria aid in the growth and development of the nematode, and the nematode help the bacteria get nutrients. The nematode itself lives in the soil and can infect a variety of insects from beetles to grasshoppers.

The cycle the bacterium and nematode go through is quite interesting. The nematode will infect an insect and release the bacterium. The bacterium will then produce toxins that kill the host. These toxins break down the tissue of the insect; the nematode can then gather its nutrients and replicate. Once the nematode has replicated and all the nutrients are gone, the bacterium will recolonize the infective juvenile nematode and the cycle continues.

Research using this system will hopefully provide a better way of protecting crops from insect pests. This also could lead to a safer insecticide. This can be achieved by studying the individual genes in X. nematophila that cause pathogenesis towards insects.

By Lacey Weaver

Image Source: Karl Ritz; License