Stigmatella aurantica

A Microbial Biorealm page on the genus Stigmatella aurantica

Classification

Higher order taxa

Bacteria; Proteobacteria; Deltaproteobacteria; Myxococcales; Cystobacterineae; Cystobacteraceae; Stigmatella

Species

NCBI: Taxonomy

Stigmatella aurantica

Description and significance

Stigmatella aurantiac is a member of myxovbacteria, which are known to have complex development and differtiating life cycles, including one as individual organism and one in a group. Myxovbacteria also have a unique ability to aggregate and move as a population has the food source becomes scarce. Single cells can be motile by “adventurous motility” and seeks other Stigmatella aurantiac . As cell density increases, the organism switches to “social motility” of cells can gather together into masses termed fruiting bodies that may consist of up to 100,000 cells. There is a physical and metabolic change when Stigmatella aurantiac form fruiting bodies. Through chemical signals between cells, the Stigmatella aurantiac develop fruiting bodies almost as a multi-cellular organism, including specialized cells and differentiation of cellular structure according to position.

Stigmatella aurantiac is a rod shaped gram negative bacterium. They are terrestrial organisms that are commonly found on rotting wood and bark. As a mesophile, they grow in moderate temperatures (between 25-40 degrees Celsius). Their ability to move as a fruiting body was a well researched topic, and led to a deeper understanding of cell to cell communication and signals. Stigmatella aurantiac also produce anti microbial compounds, such as aurafuron A and stigmatellin, which may beimportant as anti cancer agents and to produce new antibodies.

Genome structure

Stigmatella aurantiac has a circular chromosome that consists of 10.2654 million base pairs with a GC content of 67.4% and 43 pseudo genes. The chromosome is composed of DNA and codes for 8543 proteins. The gene fbfA is responsible for the fruiting body formation, allowing the structural and metabolic changes needed to form the myxospores . In experiments where the fbFA gene was deactivated, the bacterium formed structured clumps instead of fruiting bodies. The genome also produces antimicrobial compounds that can kill and lyse other microbes. This has peaked the interests of many because of the compounds potential as anti cancer agents and antibodies.

Cell structure and metabolism

Stigmatella aurantica has two distinct bodies. The vegetative cells of Stigmatella aurantica are flexible, slender rods that are5 to 8 um long and .7 and .8 wide. The fine structure resembles that of other gram negative bacteria. The cell wall is composed of a cytolplasmic membrane with a triple layered organization and a cell wall. The cell wall consists of an outer triple layer and third dense monolayer in the periplasm.

The myxospores of Stigmatella aurantica are short, fat, rods that are 1.5 to 3.5 um I length and1.1 to 1.8 um in width. There are three distinct changes that occur between these two physical states: the formation of large amounts of granules,; the formation of a capsule; and heavy folding of the outer third layer of the cell wall. The triple layer of the cell wall formed tight packs of either lamellar or vesicular organization. The change in the cell shape takes place within 10 to 15 minutes, and the fruiting body formation requires many hours during which time the cell can change its metabolism and regulate changes in the cell wall structure much more efficiently.

Stigmatella aurantica are aerobic organisms and therefore require oxygen to produce energy. Stigmatella aurantica has two food sources, decomposing wood and other microbes.. They can produce electron transport inhibitors, such as myxothiazol, the dawenols, themyxochromides, and iron chelators myxochelin A and B. These compounds can kill and lyse on microbial cell.

Ecology

Stigmatella aurantica are found on rotting wood and soil. They are capable of breaking down an wide selection of peptidoglycans, polysaccharides, proteins and other cellular detritus. They appear innature to help decompose otherwise insoluble biological debris. Stigmatella aurantica is also speculated to consume other microbes. Stigmatella aurantica can produce a variety of compounds that can kill and lyse microbial cells. By producing these antimicrobial compounds, Stigmatella aurantica maintains the balance of microbial population in the soil.

Pathology

Stigmatella aurantica is not a pathogen.

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

1) Recent research has been conducted where a new antibiotic polyketides, aurafuron A and B, were isolated from culture extracts of Stigmatella aurantic. The strains DW4/3-1 and Sg a15 were taken for their secondary metabolites. DW4/3-1 produces the electron inhibitor myxothiazol, the dawenols, the myxochromides and theiron chelators myxochelin A and B. In the Sg a15, 5 different groups ofmetabolites were discovered. These were inhibitors of the eukaryotic electron transport: the aurachins, stigmatellins, myxochelins, myxalamids and small amounts of myxochromids. In addition to the strains of Stigmatella aurantica, the new compounds, aurafuron A and B, were also isolated from a strain of the genus Archanguim. Both Aurafuron A and B were seen to inhibit the growth of filamentous fungi. Also Aurafuron B weakly active against a few Gram-positive bacteria. Both compounds were seen to be cytotoxic.

2) Secondary metabolites of myxobacteria that have been isolated, exhibit important pharmaceutical and agrochemical activities, but remain difficult to handle genetically. To utilize their metabolic potential, heterologous expression methodologies are currently being developed. The logic in the research was that if the secondary metabolites of could be combined into one organism and increase the production of these secondary metabolites. this experiment, the integration of the complete “myxothiazol biosynthetic gene cluster reconsitituted from two cosmids” from Stigmatella aurantiac. Because of factors such as GC content and codon usuage of the genes, Myxococcus Xanthus, was selected. The integration and expression of the myxothiazol genes results in the production of the secondary metabolites were comparable to the natural producer strain.

3) The unique ability of Stigmatella aurantiac to undergo a multi-cellular cycle of development to form a fruiting body has perked the research of many people. To analyze the gene responsible for this transformation, mutants defective in fruiting body formation have been induced by transposon mutagenesis using aTn5-derived transposon. This inactivates both the fbfB and fbFA genes which are both responsible for fruiting bodies. Inactivation of fbfA leads to cells that can only form structured clumps.

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by student of Rachel Larsen