Microbe Spotlight: Week 4

NDSU Microbiology
by NDSU Microbiology

The students in Infectious Disease Pathogenesis Lab will be blogging about the strange and wonderful this semester. This week's guest bloggers are: Autumn Kraft, Stephanie Kobiela, Sarah Kropp, Kaitlin Miller, and Emma Kusick. Check back next week for a new selection of microbe spotlights.

Consuming the Unsinkable Ship

After diving down to the 12,500-foot deep wreck of the RMS Titanic, scientists collected samples of rust icicles (or rusticles) in order to analyze what they were made of and what was causing this sort of formation.

In 2010, Dr. Henrietta Mann isolated and identified a never before seen organism that was present in the rusticles. This gram-negative, bacillus-shaped organism was eating away at the rust on the samples. Halomonas titanicae is certainly one of a few amazing organisms to survive thousands of feet below sea level in high pressure, high salt, and low temperature (as low as 2 degrees Celsius) conditions.

While it successfully survives in this environment, the bacterium is unfortunately destroying the wreckage of the Titanic much sooner than anticipated. However, the positives of this situation are that H. titanicae will recycle this and other sunken craft made of metal back into the environment. The organism is considered a bio-remediation agent and can clean up the metal debris at the bottom of the ocean. Other benefits to knowing about this organism, and others like it, are that now scientists can discover ways to protect our deep-sea, metal-made craft from accelerated deterioration.

By Autumn Kraft


Halobacterium salinarum NRC-1

Despite its name, Halobacterium salinarum is actually not a bacterium but a single celled, motile Archaeon. It is a Gram negative, rod-shaped organism that prefers mesophilic and aerobic conditions; it replicates via binary fission and uses flagella for motility. Halobacterium is classified as an “extremophile” because of its ability to thrive in high salinity environments.

Halobacterium was discovered in 1971 by Dieter Osterhelt, and in 2000, the entire sequence of Halobacterium sp. NRC-1 was sequenced. Today, researchers are still working to understand the organism’s extremophilic abilities and biological processes.

Some of the current applications that may apply to Halobacterium, include: 1) blending the genes of Halobacterium with various crop genes to make them more tolerant to soils with higher than average salinity conditions, 2) the use of bacteriorhodopsin (a retinal photosynthetic protein) harvested from Halobacterium
in optical security, 3) the use of bacteriorhodopsin in photobioreactors, and 4) the use of the organism as a possible biological treatment tool for high saline industrial waste in the environment.

By Stephanie Kobiela

Image: Dr. Martin Schmieder, Perth

Haloquadratum walsbyi

Haloquadratum walsbyi literally means “Walsby’s salt square.” This microorganism is classified as an archeon extremophile and lives in hypersaline solutions. H. walsbyi was discovered in 1980 by A. E. Walsby in “salt pools” near the red sea. This microorganism can be easily identified by its unique shape, a square.

H. walsbyi stains Gram negative and grows to be 1-5 microns wide. It is considered to be only two dimensional because it is only ever .1 microns in thickness. This feature helps to maximize surface area while making it easier to keep homeostasis in the hypersaline environment that it thrives in. While the microbe is not considered motile, it does contain several gas vacuoles. These vacuoles help to keep the archeon at the surface of the brine, where it will most likely find the most oxygen and sunlight.

The optimal environment for H. walsbyi is halite-dense brine found in salt pools. While the microorganism was originally discovered in pools near the Red Sea, it has since been identified in similar environments around the world. It thrives in 18% NaCl, neutral pH, 45oC, and high levels of magnesium chloride. It is most prevalent in saltwater pools where the water is evaporated off, creating very dense levels of halides. It is usually the last living organism found before the solution is considered sterile; it can make up over 80% of the biomass in these situations.

Survival of this archeon is due to a few specialized environmental adaptations. H. walsbyi creates a water-enriched capsule around itself. This capsule helps the cell to maintain its shape, aids in aerobic metabolism, and prevents desiccation from the hypersaline environment. It has specialized transporters, called supertransporters, which work overtime to ship excess chloride and phosphate molecules out of the cell. It collects light as an alternative energy source using specialized transmembrane proteins. Its shape also adds to this alternative energy source, allowing it to work like a solar panel in anoxic environments.

Much research regarding Haloquadratum walsbyi has commenced since scientists figured out how to culture it. It hasn’t been found to be pathogenic to humans, but it is resistant to many common antibiotics. It is a very extreme and unique organism; and there is much more to be learned about this microbe.

By Sarah Kropp

Image: Rotational

Metabacterium polyspora

Metabacterium polyspora is a Gram positive, spore-forming bacilli that was discovered in 1913. It ranges in size from 15 to 35 µm long and is the closest known relative to the largest bacterium known, Epulopiscium spp. M. polyspora can form as many as two to nine endospores per cell, while most endospore-forming bacteria produce only one spore per cell. It forms a symbiotic relationship with guinea pigs while living in their upper GI tract. This bacterium is unable to be cultured in the lab, so little information is known about it.

M. polyspora’s life cycle is dependent on guinea pigs because they consume feces that contain the M. polyspora endospores. The bacterium travels to the upper GI tract where it bypasses binary fission and begins forming forepores. The forespores travel to the cecum where they mature into endospores. The mature endospores then travel through the colon and exit the body with the feces. M. polyspora can only survive if the feces are consumed so the life cycle can occur again. Usually endospores are only produced by bacteria in times of stress, however, M. polyspora constantly produces endospores as a way of reproduction.

By Kaitlin Miller

Image: Selbst

Magnetospirillum magnetotacticum

If you think that magnetism is the sole property of certain inanimate objects, then you haven’t heard of the bacterium, Magnetospirillum magnetotacticum, the “Living Magnet.”

This Gram negative, denitrifying bacterium is found in the oxic-anoxic transition zone of the upper sediment layers of freshwater systems. The bacterium can be classified as a magnetotactic bacterium, which means that its mobility is based on magnetic characteristics. Iron is taken up into the cell and mineralized to form magnetite crystals that allow M. magnetotacticum to orientate itself toward optimal environmental conditions such as reduced oxygen levels and high reduction potentials.

Scientists hope to further study this bacterium and be able to use it for Bioprecipitation, Bioremediation, Geobiological traces, and magnetic targeting of pharmaceuticals.

By Emma Kusick

Image: Zeiss Microscopy