Hongwei Yu and Nathan E. Head

Department of Microbiology, Immunology and Molecular Genetics, Joan C. Edwards School of Medicine at Marshall University, 1542 Spring Valley Drive, Huntington, WV 25704

FIGURES

Figure 1. Schematic diagram of the entire genome of P. aeruginosa strain PAO1 according to http://www.pseudomonas.com/. The scale on the outmost circle is in Mb. Outer and inner circles consist of SpeI and XbaI digested fragments assembled in order, respectively. Known SpeI fragments (also see table 2) are labeled in the outer circle with respective alphabetic letters. Locations of 2 probable bacterial phages (23), P. aeruginosa genomic island-1 (PAGI-1) (78), a flagellin glycosylation island (77), and 3 genetic loci (23) proposed to be involved in the regulation of alginate production along with algD and algU loci are noted.

Figure 2. A hypothetic process of P. aeruginosa colonization leading to biofilm formation in CF. Flagella-mediated motility is involved in the initial attachment (30, 51). Type 4 pili (30) and a quorum sensing signal (3OC₁₂-HSL) (40) participate in microcolony differentiation. Overproduction of alginate, which results in the formation of mature biofilms, can be caused by the mucA mutations induced through stresses such as oxidants released by PMN's (43). The level of C₄-HSL is increased in mature biofilms (26). Sessile cells can be sloughed off as planktonic cells due to mechanical factors (ex. coughing). Biofilms formed as a result of mediations through motility, quorum sensing and overproduction of alginate may be different from each other physiologically, and may represent various snapshots of a bacterial developmental process.

Figure 3. A persistent infection phenotype expressed by P. aeruginosa due to the excessive production of alginate. Alginate helps to maintain the three dimensional architecture of mature biofilms known to be resistant to host defenses and antibiotics. Shown is a mucoid colony morphology from a clinical CF isolate of P. aeruginosa growing on a laboratory media.

Figure 4. Transmission electron micrograph of a thin-section of a postmortem lung sample from a CF patient. Shown is P. aeruginosa in mature biofilms, a persistent infection phenotype closely associated with chronic bacterial lung infections in CF. P. aeruginosa is embedded within a mucous matrix produced by bacteria and host [Reproduced with permission from Lam et al. (25)].

Figure 5. Separation of SpeI digested P. aeruginosa chromosomal DNA by PFGE. (A). CF006 and CF007, two clinical CF isolates display the genomic diversity that exists throughout the majority of clinical isolates. Environmental strains (ENV42: Japan, and PAOH: Ohio River) of P. aeruginosa also exhibit a diverse chromosome. (B). Burn isolates PAO1 and PA14 also possess diversity along the chromosome. Clinical sequential isolation of P. aeruginosa shows conservation of genome throughout colonization (CF041: initial isolate in 1990, CF042: isolated in 1994, CF043: isolated in 1998).