Eikenella corrodens
A Microbial Biorealm page on the genus Eikenella corrodens
Classification
Higher order taxa
Bacteria; Proteobacteria; Betaproteobacteria; Neisseriales; Neisseriaceae; Eikenella
Species
Eikenella corrodensDescription and significance
Eikenella corrodens is a periodontopathogen that inhibits the human oral cavity, intestinal tract, and genital tract. It was first isolated by Henriksen in 1948 and was first classified as Bacteriode corrodens by Eiken in 1958. In 1972, Jackson and Goodman renamed it “Eikenella corrodens” to avoid mixing it up with Bacteroides ureolyticus. Eikenella corrodens exists in colonies that typically release a musty or bleachy smell [12]. It grows at a temperature from 35oC to 37oC. Its strain type is ATCC 23834, DSM 8340 [8]. Eikenella corrodens’s plasmid DNA, pMU1, is used in various researches such as on pilus-formation and colony morphology [2]. Under a microscope, one can see three different regions of Eikenella corrodens: a clear and moist center, a visible ring that appears as droplet, and an outer growth ring. A unique feature of this bacterium is that it is capable of corroding agar plate culture; hence, the species name is corroden [4]. Eikenella corrodens exists in dental plaque of both healthy people and periodontitis patients and can cause infections. Other clinical sources include head and neck infections and respiratory tract infections. Furthermore, it is responsible for about one quarter of all human hand bites infections and clenched-fist injuries [12].
Genome structure
Eikenella corrodens has a genome with a length of 8696 nt and has a 55% coding. It has circular DNA chromosome and no RNA. Plasmids have been identified in this bacterium and were labeled pMU1. Plastmid pMU1 has been widely used in various researches such as colony morphology and pilus formation. Eikenella corrodens chromosome sequence was completed on June 6, 2005 at the Hiroyuki Azakami, Yamaguchi University, Department of Biological Chemistry, Japan [12]. Although the sequence has been completed, the amount of base pairs and/ or the number of chromosomes are still unknown.
Cell structure and metabolism
Eikenella corrodens is a Gram negative, facultative and anaerobic, non-motile, non-sporeforming pathogenic bacillus that exists in the form of a straight rod. E. corrodens has DNA chromosomes and plasmids but no RNA [4]. Its plasmid, especially pMU1, is a useful source in Eikenella corrodens studies [2]. This bacterium can survive under both aerobic and anaerobic conditions. However, under aerobic condition, it requires the presence of Hemin (a heme oxygenaase) for growth. Growth on plates may be stimulated in a 3-10% CO2 environment, even though CO2 is not required [4]. An important characteristic of Eikenella corrodens is that it is oxidase positive, which means that it can reduces nitrate to nitrite. This characteristic is important because E. corrodens generates energy mainly via oxidative deamination of proline in the oral cavity. A chemostat-growth experiment, with chemically defined media of different quantity of proline, verifies that this amino acid is the main source of ATP generation in Eikenella corroden. The biomass production per mole of proline is higher than any other amino acids. This bacterium generates proline by producing the enzyme proline iminopeptidase, which discharges the side-chain proline from the N-terminus of polypeptides [7].
Ecology
The interaction of Eikenella corrodens and other subginival organisms may be fatal to patients with Down syndrome. Down syndrome children often develop severe periodontal disease at an early stage in their lives. Studies show that certain periodontopathogens, such as Eikenella corrodens, began to colonize in the oral cavity of children with Down syndrome. Eventually, with the parallel maturation of subgingival components such as P. gingivalis, these children will be more susceptible to gingival inflammation [1]. Antibiotic such as tetracycline is often used to treat Eikenella corrodens infections. However, a recent study done by a group of doctors at the National Taiwan University confirms that this antibiotic cannot eliminate the bacterium completely. Periodontopathogens may re-infect the periodontal pockets in the oral cavity as soon as three months after the termination of the treatment. Thus, tetracycline has no real affect on Eikenella corrodens [9].
Pathology
Since Eikenella corrodens inhabits the human oral cavity, intestinal tract, and genital tracts, any breakage in barriers (mucosal membranes, skin, etc) will be the prefect target for hematogenous spread and vital Eikenella infections. Prior illness that drained antibodies from the body immune system is also a perfect condition for Eikenella corrodens to invade; thus this bacterium is an opportunistic human pathogen [5]. After the bacterium invaded the membrane, it will cause inflammation and pain. Symptoms of Eikenella corrodens infection may be an onset of swelling, chills, high fever that lasts for days, local tenderness, and edema. Eikenella corrodens infection may lead to serious diseases such as periodontitis, osteomyelitis, meningitis, empyema, and endocarditis. Infections causes by this bacterium can be treated with antibiotics such as penicillin, ampicillin, and tetracycline [10].
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
Enter summaries of the most recent research here--at least three required
References
Edited by student of Rachel Larsen
