Trying to find the most intriguing and interesting organisms while also competing to "stump the chump" I came across the organism Picrophilus. From the name one could probably guess as to what Picrophilus is. Picrophilus was the name given on the account that picro means "acid" and philic or philus means "lover." This organism was first isolated from the solfataric environments of northern Japan.
According to the published reports, samples containing the acid lover were first collected from a solfataric spring in Noborribetsu, from a geothermally heated basin with sulfurous deposits at Kawayu Onsen, and also from a dry, hot soil in Kawayu, all which are located in northern Japan. These areas are all suitable environments in that they include both heat and low pH soil. Although not a thermophile by definition, it does prefer temperatures above room temp. The original temperature that these organisms were first collected had temperatures ranging from 50 to 60°C, while the pH was recorded at 2.2 for the first two places and an astounding 0.5 from the latter. Although Picrophilus grew between the 45 and 65°C, its optimum temperature was 60°C. However there wasn't any growth at 40 or 67°C. Also from tests performed on this organism it was clearly shown it only grew at pHs below 3.5, while its optimal pH was at 0.7. Even more astounding is that Picrophilus can grow well at a pH of 0.0!
When electron microscopy was used, the areas of the cell displaying a low electron density consequently appeared as a cavity. The cavity is perhaps maybe a vacuole of some sort. The morphology of the organism is irregular cocci of around 1 to 1.5 µm in diameter, its wall contains an S-layer which of course is characteristic of many Archae. The S-layer of Picrophilus is what distinguishes it from Thermoplasma. The thermoacidophilic archaeon, Thermoplasma, was believed to resemble Picrophilus, yet further observations led to its separation based on its S-layer. Because of the S-layer Picrophilus 1) has a highly filigreed regular tetragonal shape and 2) has the ability to survive at extremely acidic levels, levels lower than any other organism, Also on its S-layer, there were "brush-like" structures present on its cytoplasmic membrane possibly consisting of long polysaccharide chains. Neither pili nor flagella have been observed on it.
The metabolic properties of Picrophilus indicate that it grows well heterotrophically under aerobic conditions on 0.2% yeast extract. Picrophilus is considered strictly an aerobic organism. The growing media are long, drawn out discussions, so for simplicity let's just say the organism is quite picky. Sugar and other such macromolecules are not essential for its growth in fact they are actually inhibitory. In fact growth was inhibited by a variety of substances; sugars, starches, sucrose, or lactose alone, Casamino Acids, and also when carbon sources were supplemented with vitamins,
In conclusion, the most important part of this paper is the reasons in which I chose this organism. I found it absolutely fascinating that this organism could grow at a pH of 0, although not its optimal pH. For the simple reason there aren't any others that can do this makes it all the more interesting. This organism helps to keep interest in bacteria and microbes growing due to the fact I don't believe there exists one single place where bacteria can't be found.
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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