The opportunistic pathogen Pseudomonas aeruginosa

Pseudomonas aeruginosa is a gram negative, aerobic, polarly flagellated bacillus [1]. It is a common inhabitant of soil, water, plants, animals and is an opportunistic pathogen, causing wound, burn, and urinary tract infections in humans. Infections by P. aeruginosa are a great risk for burn victims, where it’s the single greatest cause of death [1]. Cancer, cystic fibrosis, and chemotherapy patients are also at risk. P. aeruginosa is particularly dangerous in hospitals as it is unusually resistant to antibiotics [1].

In 2000 the sequencing of the large 6.3Mbp genome was completed with gene analysis predicting 5570 genes [2]. This approaches the genetic complexity of the simple eukaryote Saccharomyces cerevisiae, whose genome encodes about 6,200 proteins [2]. However, only 54.2% of the genes could be assigned a function [2]. Of the unidentified genes 38% appeared to be unique to P. aeruginosa as they are not homologous with any reported gene sequence. As only genes of known function can be discussed only half the genetics of P. aeruginosa can be described at present. P. aeruginosa is predicted to have all the housekeeping genes for protein synthesis, DNA replication, amino acid synthesis, etc as do other bacteria. However it does have a disproportionately high number of outer membrane protein genes compared with other bacteria, a very large number of genes involved in the uptake of nutrients, a large number of genes involved in β oxidative metabolism, four multi-drug efflux systems, three protein secretion systems, and four chemosensing and chemotaxis systems [2]. The huge array of genetic systems available to P. aeruginosa goes a long way to explaining its ubiquitous and opportunistic pathogenic nature.


  1. Lim, D. (1998) Procaryotes: The bacteria and the archaea. In: Microbiology. 2nd ed. pp. 319-320. WBC / McGraw-Hill.
  2. Stover, C.K., Pham, X.Q., Erwin, A.L., Mizoguchi, S.D., Warrener, P., Hickey, M. J., Brinkman, F.S.L., Hufnagle, W.O.D., Kowalik, J., Lagrou, M., Garber, R.L., Goltry, L., Tolentino, E., Westbrock-Wadman, S., Yuan, Y., Brody, L.L., Coulter, S.N., Folger, K.R., Kas, A., Larbig, K., Lim, R., Smith, K., Spencer, D., Wong, G.K.-S., Wu, Z., Paulsenk, I.T., Reizer, J., Saier, M.H., Hancock, R.E.W., Lory, S. & Olson, M.V. (2000) Complete genome sequence of Pseudomonas aeruginosa PAO1, an opportunistic pathogen. Nature. 406:959-964.

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