Clostridium sticklandii

Clostridium sticklandii is an anaerobic, motile, gram-positive bacterium. It was first isolated in 1954 from the black mud of the San Francisco Bay Area by T.C. Stadtman, who also named the species.[1] Cl. sticklandii is not pathogenic in humans.

Clostridium sticklandii
Scientific classification
Kingdom:
Bacteria
Division:
Firmicutes
Class:
Clostridia
Family:
Clostridiaceae
Genus:
Clostridium
Species:
Cl. sticklandii
Binomial name
Clostridium sticklandii
Stadtman and McClung 1957 (Approved Lists 1980)

Biology and biochemistry

Cl. sticklandii ferment amino acids by using the Stickland reaction, which couples the oxidation of one amino acid and the reduction of another. L.H. Stickland described this process in 1934. The enzymes in the Stickland reaction are D-proline reductase (an electron acceptor) and Glycine reductase. Cl. sticklandii preferentially utilize threonine, arginine, serine, cysteine, proline, and glycine during the growth phase and lysine during the stationary phase, while excreting glutamate, aspartate and alanine.

Selenoproteins can be found in the genome of Cl. sticklandii. One such selenoprotein, glycine reductase A was first identified in Cl. sticklandii. C. sticklandii uses a total of eight of these selenoproteins. One of which, PrdC, was not previously thought to be a selenoprotein. PrdC, which is similar to RnfC in other species, is found within the D-proline reductase operon. The D-proline reductase operon is responsible for the reductive ring cleavage of D-proline into 5-aminovalerate. 5-aminovalerate is excreted by Cl. sticklandii.

Although energy conservation in Cl. sticklandii is achieved through substrate level phosphorylation, it can be achieved via electron-transport phosphorylation as well. The Rnf complex, a Na+-dependent F-ATPase, V-ATPase, and a membrane-bound Pyrophosphatase serve as methods to conserve energy through electron-transport phosphorylation.

On another interesting note, Cl. sticklandii have two carbon dioxide fixation pathways, Wood-Ljundgahl and Glycine synthase/glycine reductase pathways. It is an oddity to find both of these methods of carbon dioxide fixation simultaneously. Only four other bacterial species have been observed to contain both of these pathways. Although, Cl. sticklandii has the ability to utilize both pathways, it has not been determined if they do utilize both pathways at the same time.

Genome

Clostridium sticklandii has a genome that consists of one circular chromosome. On this chromosome are 2,715,461 base pairs. Of these base pairs there are 2573 coding sequences with only 2.1% of the genome repeated. Clostridium sticklandii shares the highest number of genes that are homologous with Clostridium difficile (a pathogenic species of Clostridia') and with two members of the genus Alkaliphilus.[2]

Although it is considered a obligate anaerobe, Cl. sticklandii has genes that allow for the bacterium to be cultivated in aerobic conditions. Some of the proteins made by Cl. sticklandii that allow for the repair of damage from oxygen exposure include Mn-superoxide dismutase[3] and Superoxide reductase, alkyl hydroperoxide reductase,[4] rubrerythrin,[5] Glutathione peroxidases, seleno-peroxiredoxin, thioredoxin-dependent peroxidase, and sulfoxide reductases A and B.

Notes
  1. Fonknechten, N; Chaussonnerie, S; et al. (2010). "Clostridium sticklandii, a specialist in amino acid degradation: revisiting its metabolism through its genome sequence". BMC Genomics. 11: 555–567. doi:10.1186/1471-2164-11-555. PMC 3091704. PMID 20937090.
  2. "alkme".
  3. "scripps". Archived from the original on 2012-07-23. Retrieved 2012-04-03.
  4. "sgmjournals".

References
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