Thiothrix nivea

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A Microbial Biorealm page on the genus Thiothrix nivea

Classification

Figure 1: “Rosette of T. nivea strain JP2 grown in MP broth and transferred to an agar-covered slide for photography.”3

Higher order taxa

Bacteria; Proteobacteria; Gammaproteobacteria; Thiotrichales; Thiotrichaceae; Thiothrix ¹

Species

Thiothrix nivea

Description and significance

Thiothrix nivea is the type species for the Thiothrix genera. It was first described in 1888 by the Russian microbiologist, Sergey Nikolayevich Winogradsky. Winogradsky was one of the first evironmental microbiologists to have studied nonpathogenic microbes. At the time of T. nivea's discovery he had been doing research on various types of sulfur bacteria.² T. nivea cells can be found in sulfur containing flowing water, such as sulfur springs, deep sea vents, and waste water treatment plants. It is not known to be pathogenic, likely due to its metabolic needs of constant sulfur flow, and to the fact that it has been found to exist in temperatures of no more than 32-34 °C.¹ None of which are found within the human body.

Genome structure

Thiothrix nivea's genome was completely mapped by the US Department of Energy's DOE Joint Genome Institute. The genome was found to contain about 4.7 mega-base pairs. The genome contains 4,594 total genes with 4,542 of those coding for proteins, that comes out to 98.87% protein coding genes. The genome has a G/C ratio of 54.87%. ³

Cell and colony structure

Micrograph of T. nivea rosettes and extending filaments.⁴

Thiothrix nivea is a 1-1.5 µm rod-shaped gram negative bacteria. When in the presence of sulfate or thiosulfate, sulfur granules are deposited in invaginations of the cytoplasmic membrane, external to the cytoplasm. Each cell has a tuft of fimbriae which anchors it to the cell beside it, and the colony to the substrate they may be growing on. Cells do not exhibit flagella. Cells grow and divide in a gliding motion enclosed within sheaths producing filamentous structures. When cells are clumped together, their division produces rosettes.⁴

Metabolism

Thiothrix nivea is an aerobic bacteria, producing energy both heterotrophically and autotrophically. Cells require "both a reduced sulfur compound and an organic substrate for growth."⁵ Because of this cells are considered to be an obligate mixotroph, obtaining energy from "the oxidation of sulfide or thiosulfate and carbon from CO² and organic compounds."⁴ The organic compounds used as the sole carbon sources are acetate, malate, pyruvate and oxalacetate. The necessary sources of reduced sulfur were found to be sulfide and thiosulfate, which is deposited within the cell in granules to be used in times of need. Nitrogen sources were found to be ammonia, nitrate ^1&4 and potassium nitrate.¹ In culture cells do not hydrolyze starch, geletin, or casein.⁴

Ecology

T. nivea is found free living in sulfide containing flowing waters such as sulfur springs, deep sea hydrothermal vents and is most well known for its populations in sewage waste water.³ T. nivea has been found to thrive within an optimal pH of 7.5 and temperatures ranging from 25-30 °C. ⁵ Cells have been found to withstand temperatures of minimally 6-8 °C and maximally 32-34 °C.¹

References

1) Gerrity, George. (2005) Bergey's Manual of Sytematic Bacteriology: Volume 2 - The Proteobacteria Part B The Gammaproteobacteria. 2nd Ed. Volume 2. New York: Springer. pp 134-141. Ebook

2) "Sergey Nikolayevich Winogradsky."(2013) Encyclopædia Britannica. Encyclopædia Britannica Online Academic Edition. Encyclopædia Britannica Inc. Encyclopædia Britannica.

3) "Thiothrix nivea JP2, DSM 5205 ." Integrated Microbial Genomes (2011): n.pag. DOE Joint Genome Institute. Integrated Microbial Genome.

4)Larkin, John, and Dean Sinabarger. (1983) "Characterization of Thiothrix nivea." International Journal ofSystematic Bacteriology. Volume 33. Issue 4. : pp 841-846. Journal

5) Rossetti, Simona, Linda Blackall, et al. (2003) "Phylogenetic and physiological characterization of a heterotrophic, chemolithoautotrophic Thiothrix strain isolated from activated sludge." International Journal of Systematic and Evolutionary Microbiology. Journal. DOI 10.1099/ijs.0.02647-0

Edited by Brittany N King, student of Dr. Lisa R. Moore, University of Southern Maine, Department of Biological Sciences, University of Southern Maine Biology Department Website