Clostridium limosum

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1. Classification

a. Higher order taxa

Bacteria; Firmicutes; Clostridia; Eubacteriales; Clostridiaceae; Hathewaya (1)

2. Description and significance

Clostridium limosum is a Gram-positive bacterium that has large, straight, rod-shaped cells. C. limosum is found in soil, but it has also been known to infect humans and animals such as cattle, farm minks, and chickens (2) (3). The pathogenic properties are still a source of current research as the route of transmission is not fully understood, with a special focus on potential foodborne illness, because of the clinical disease implications in livestock (2) (4). C. limosum is a close relative of Clostridium botulinum, the bacteria that cause the illness of botulism via a toxin that attacks the nervous system (2). However, treatment for botulism does not successfully treat a C. limosum infection, making the comparison between the two a source of interest (2). There is previous evidence of human infection in lung abscesses as a part of a mixed infection (5) (6). C. limosum infections within humans are known to be exceedingly rare, but carry a large risk of future complications and occasionally death (6).

3. Genome structure

The complete genome was sequenced from a Clostridium limosum strain that was isolated from the intestinal tissues of a group of cows that suffered from a potential blackleg outbreak in Germany, 2014 (4). The genome of this strain (14S0207) consists of a circular chromosome and three plasmids of varying sizes and numbers of genes. The circular chromosome is 2.95Mb, containing 33 rRNAs, 92 tRNAs, four other RNAs, 2718 genes, and 62 pseudogenes (4). A streptolysin-related gene cluster found in the chromosome codes for a streptolysin S homolog (which encodes 52 amino acids), a bacteriocin, and a virulence factor that can cause hemolytic or cytolytic activity in the infected host cells. On the other hand, the first plasmid (0.14 Mb) contains 125 proteins, 132 genes, and 7 pseudogenes; the second plasmid (0.04 Mb) contains 54 proteins, 58 genes, and 4 pseudogenes; the third plasmid (0.03 Mb) contains 30 proteins, 31 genes, and one pseudogene (4). None of the three different plasmids carries any rRNA or tRNA information. Each of the four components of C. limosum has similar guanine-cytosine content and the overall guanine-cytosine content for the genome is 24.0 mol% (4). There are three highly conserved proteins within the genus of Clostridium that contain three highly conserved indels: a four-amino-acid insert in DNA gyrase, one- amino-acid deletion in ATP synthase beta subunit, and a one-amino-acid insert in ribosomal protein S2 (3). A C3 transferase exoenzyme obtained from a human pathogenic strain of C. limosum catalyzes ADP-ribosylation, a mechanism that the bacteria use to attack eukaryotic cells and modify their regulatory proteins (5).

4. Cell structure

Interesting features of cell structure. Can be combined with “metabolic processes”

5. Metabolic processes

Describe important sources of energy, electrons, and carbon (i.e. trophy) for the organism/organisms you are focusing on, as well as important molecules it/they synthesize(s).

6. Ecology

Habitat; symbiosis; contributions to the environment.

7. Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

8. Current Research

Include information about how this microbe (or related microbes) are currently being studied and for what purpose

9. References

It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.