Higher order taxa: Domain: Bacteria | Phylum: Proteobacteria | Class: Epsilonproteobacteria | Order: Campylobacteraceae | Genus: Campylobacter Species: Campylobacter ureolyticus
2. Description and significance
Campylobacter ureolyticus, which used to be known as Bacteroides ureolyticus, has been recently classified (1). C.ureolyticus is of the genus, Campylobacter, which is known to be a foodborne pathogen and the cause of zoonotic diseases, a disease that exists in animals and can be transmitted to humans, worldwide. C.ureolyticus specifically has also been found to be a gastrointestinal pathogen of humans (4). C.ureolyticus is less virulent compared to the other flagellate species of Campylobacter, for example, C.jejuni (4). Furthermore, research shows showed that C.ureolyticus was the second most common causative agent of Campylobacter related gastroenteritis, outranking C.coli. ( 3 and 4 ). Consequently, this presents the need to conduct extensive research on this organism that poses as a serious threat to the health of humans.
3. Genome structure
A 16S rRNA sequence similarity of C. ureolyticus was found within the range of 91–93% to the species of the genus, Campylobacter. This contributed to the reclassification of C.ureolyticus. Recent studies suggest that C. ureolyticus includes species that are characterized by DNA alone, similar to those observed in C.concisus (4). The genome for C.ureolyticus was obtained from its strain RIGS 9880, which was isolated in patients with gastroenteritis (9).The genome of this strain is circular, 1,642 kbp in size, and has a G:C content of 29.23% (9). It econdes 1,595 putative protein coding genes, which are genes that code for an unknown protein with an unknown function, 24 pseudogenes, and 3 rRNA operons (9). Additionally, it lacks genes that code for flagella related proteins and glutamine amido transferases, which is important in the pyrimidine biosynthetic pathway(9). There are two C. ureolyticus strains whose genomes are currently available on databases, DSMZ 20703 and ACS-301-V-Sch3b (3). The genomes of these stains are 1.74 Mb and 1.66 Mb respectively, but only 18.8% and 17.1% of the protein coding sequence of these strains are not found in the other. 75-79.5% of proteins were found to be highly conserved between these two strains. Also, whole genome comparison of the protein encoding sequences of the two C. ureolyticus strains against other members of the same genus shows conservation across the different species of Campylobacter, with 9–22% of gene products conserved in protein encoding sequences (4). The largest number of conserved protein homologs were found in C. concisus, and the lowest in C. upsaliensis (4). There were 128 protein coding sequences identified as being highly conserved across all species of Campylobacter when DSMZ 20703 was used as the reference genome (4). These protein coding sequences are involved in the production of membrane bound transporters, respiration, metabolism of macromolecules, and stress response mechanisms (4).
4. Cell structure
Campylobacter ureolyticus shares many phenotypic characteristics with other Campylobacter species (10). Campylobacter ureolyticus are gram-negative bacteria, that are non-spore forming, spiral shaped rods which usually range from 0.5 to 5 microns long and 0.2 to 0.9 microns wide (4). The cells are motile and anaerobic; however, unlike most of the Campylobacter species Campylobacter ureolyticus do not have flagella and differ in fatty acid composition(4). Bullman et al. found that Campylobacter ureolyticus has 288 proteins with 25 of them having virulent functionalities (4). Campylobacter ureolyticus was also identified as having 13 hemolytic cytotoxin and cytolysin proteins. The function of these proteins, involved in the secretion I pathway, are regulated by the Ca ion concentrations within and outside of the cell (4).
5. Metabolic processes
Campylobacter ureolyticus are strict anaerobes which do not oxidize or ferment carbohydrates (4). Unlike most of the Campylobacter species Campylobacter ureolyticus have the ability to hydrolyze gelatin and casein. In a 2010 publication by Vandamme et al. Campylobacter ureolyticus was found to also metabolize urea (10).
Campylobacter ureolyticus are oral and intestinal commensals of animals, which makes it hard to control infections caused by these microbes (6). Being unable to grow in number outside animal bodies, Campylobacter family serves as a sign of recent contamination with animal feces and exist widely in the environment, especially in water (7). In the river, Campylobacter species are found least in rural and fast-flowing region, while found most in regions near or downstream of sewage works (8). As an evidence of Campylobacter originated from animal feces, the number of Campylobacter increased when rainfall caused farmland water to flow into the river (8).
Campylobacter ureolyticus has been identified as a gastrointestinal pathogen (4). Being a gastrointestinal pathogen, C. ureolyticus is thought to be related to inflammatory bowel diseases, including Crohn’s disease and ulcerative colitis (13). When Crohn’s disease patients were analyzed, four Campylobacter species were isolated from the patients and one of them was C. ureolyticus, indicating an existence of a relationship between Crohn’s disease and C. ureolyticus (13). Recent studies also show that its incidence in gastrointestinal related illnesses may be related to other diseases in immunocompromised patients and diabetes patients (4). Campylobacter’s major transmission pathways to humans include poultry, water, and animals (5). The prevalence of Campylobacteriosis, a general term that describes infections caused by Campylobacter genus, has increased in the entire world for past years and the research indicates that Campylobacteriosis is endemic in Africa, Asia, and the Middle East, especially in children (5). Campylobacteriosis usually accompanies symptoms of diarrhea since Campylobacter genus is a gastrointestinal pathogen (5).
Campylobacter species are found in higher concentration in a region with unpurified water than the region with purified water (7). Drinking purified water can reduce the chance of being infected by Campylobacter species. As the species of Campylobacter family are transmitted to humans by poultry, water and animals, being careful and sanitizing after contact with animals can reduce the chance of infection (5).
9. Current Research
In the last few years, different research worldwide has been conducted to understand different species in the Campylobacter genus, including Campylobacter Ureolyticus. Research that aid to obtain information in how species of the Campylobacter genus are associated with children with diarrhea(11), and initiation of inflammatory bowel disease(10). Research conducted in Sydney, Australia found in 2016 that Campylobacter Ureolyticus has a gene that encoded for a protein called zonula occludens toxin (Zot). The Zot protein cause damage to the intestinal epithelial cells(10). A study performed in Japan in 2017, used samples from hospitalized children and found that Campylobacter Ureolyticus is one of the pathogenic bacteria associated with children with diarrhea. However, other Campylobacter species were also investigated including C. jejuni and C. coli which were not as highly prevalence compare to C. Ureolyticus in children with diarrhea (11).
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(2) Lui F., Ma R. N., Wang Y. M. , & Zhang L. 2018. The clinical importance of Campylobacter concisus and other human hosted Campylobacter species. Frontiers In Cellular And Infection Microbiology 8: 243.
(3) Bullman, S., Lucid, A., Corcoran, D., Sleator, R. D., & Lucey, B. 2013. Genomic Investigation into Strain Heterogeneity and Pathogenic Potential of the Emerging Gastrointestinal Pathogen Campylobacter ureolyticus. PLoS ONE, 8:e71515.
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(8) Bolton, F. J., Coates, D., Hutchinson, D. N., & Godfree, A. F. 1987. A study of thermophilic campylobacters in a river system. Journal of Applied Microbiology,62:167-176.
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