DNA Information
As a reminder, Pseudomonas aeruginosa is a pathogenic Gram-negative bacterial pathogen that causes severe nosocomial lesions. P. aeruginosa is known to contain only one circular chromosome and multiple plasmids with additional functions for the bacterium (Klockgether et al., 2011). According to a study at NCBI, the genome size is 6.3 Mb — 6264404 to be exact — with a total number of genes not exceeding 5697. It is assumed that the total number of sequence reads is 54, and the average protein count is 6074. Finally, one of the most important characteristics is the GC content: for Pseudomonas aeruginosa, this value is 66.2%. The number of rRNAs and tRNAs is 13 and 63, respectively, with a total of 30 remaining RNA forms (Pseudomonas aeruginosa, n.d.). Thus, P. aeruginosa is a single-chromosomal bacterium with a relatively large number of active genes.
Virulence
As stated, Pseudomonas aeruginosa contains 5,697 genes, of which 19 are pseudogenes. This means that less than 0.33 percent of the total number of genes turn out to be rudimentary, that is, incapable of encoding a protein and not actually performing any function within the bacterial cell. Consequently, more than 99.67 percent of the genes in Pseudomonas aeruginosa are functional, and some of them may be virulent, that is, contributing to parasitization within victims. The data show that fourteen common virulent genes are characteristic of Pseudomonas aeruginosa. These include, with indicated probability of occurrence, algD N (100%), plcH N (100%), plcN N (100%), lasB N (100%), exoT N (100%), apr N (99%), lasI N (98%), lasR N (97%), exoY N (94%), algU N (82%), rhII N (82%), rhRI N (81%), exoS N (76%), exoU N (31. 1%) (Alonso et al, 2020). These data clearly show that some of them had the highest frequency of occurrence, while others — e.g., exoU N, which was present in only 28 of the 90 strains observed — were the least common in Pseudomonas aeruginosa. Each of the genes above has the ability to form biofilms, which differ in their danger to the patient’s body. However, there is also mediated virulence, in which the presence of certain proteins or even cell organoids can induce a host response. These, with respect to Pseudomonas aeruginosa, include flagella, exotoxins, phospholipase C and protease A, QS proteins, elastase, and some other examples of natural forms within the bacterium (Alonso et al., 2020). Thus, several pathogenicity factors are true for Pseudomonas aeruginosa, which means that the virulence spectrum of the bacterium is considerable.
Genomic Mutations of Pseudomonas aeruginosa
In fact, Pseudomonas aeruginosa shows high resistance — or low susceptibility — to a number of popular antibiotics used for therapy. Interesting data show that Pseudomonas aeruginosa has been characterized over time (after 2001) by an increase in non-synonymous mutations that cause resistance to popular antibiotics (Wee et al., 2018). These primarily include, according to Palmer & Whiteley (2015), β-lactams, aminoglycosides, and polymyxins. Such effects are only made possible by forced mutations that result in immunity to the agents. Mutations in the orfN gene have been shown to have a high frequency compared to more conserved genes (Sanz-GarcÃa et al., 2018). This may be an indication of the high frequency of orfN presence in the Pseudomonas aeruginosa genome or the adaptation of the pathogen to the need for a constant synthesis of the corresponding protein.
References
Alonso, B., Fernández-Barat, L., Di Domenico, E. G., MarÃn, M., Cercenado, E., Merino, I., … & Guembe, M. (2020). Characterization of the virulence of Pseudomonas aeruginosa strains causing ventilator-associated pneumonia. BMC Infectious Diseases, 20(1), 1-8.
Klockgether, J., Cramer, N., Wiehlmann, L., Davenport, C. F., & Tümmler, B. (2011).
Pseudomonas aeruginosa genomic structure and diversity. Frontiers in Microbiology, 2(150), 1-18.
Palmer, G. C., & Whiteley, M. (2015). Metabolism and pathogenicity of Pseudomonas aeruginosa infections in the lungs of individuals with cystic fibrosis. Microbiology Spectrum, 3(4), 3-4.
Pseudomonas aeruginosa. (n.d.). NCBI. Web.
Sanz-GarcÃa, F., Hernando-Amado, S., & MartÃnez, J. L. (2018). Mutational evolution of Pseudomonas aeruginosa resistance to ribosome-targeting antibiotics. Frontiers in Genetics, 9(451), 1-17.
Wee, B. A., Tai, A. S., Sherrard, L. J., Zakour, N. L. B., Hanks, K. R., Kidd, T. J.,… & Beatson, S. A. (2018). Whole genome sequencing reveals the emergence of a Pseudomonas aeruginosa shared strain sub-lineage among patients treated within a single cystic fibrosis centre. BMC Genomics, 19(1), 1-11.