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Pseudomonas aeruginosa produces pyoverdine in order to chelate iron, the ferri-pyoverdine complexes formed are internalized by ferripyoverdine transporters (fpvA) present on its outer membrane, three fpvAâs are known (fpvAI, fpvAII, and fpvAIII), the fpvAI was cloned in 1993 by Poole et al. and the other two fpvAâs were cloned by De Chial et al. 2003. Following the speculation that some pyoverdine negative Pseudomonas aeruginosa isolates present in the lungs of cystic fibrosis patients ( De Vos et al. 2001) and that an fpva mutant were growth stimulated by iron, an alternative receptor, termed fpvB was identified by Ghysels et al. 2004. A fragment of this gene was determined by Polymerase Chain Reaction, (PCR). For the first time, using PCR procedures, the complete fpvA and fpvB gene sequences were determined and the sequences from this determination have been deposited in the GenBank database (Bodilis et al. 2009) and some variants of these receptor genes are presented.
The ferripyoverdine receptors is permeable for a number of compounds which may or maynot be beneficial for Pseudomonas aeruginosa, the ferri-pyoverdine receptor route in addition to serving as entrance for antibiotics, also serve as entrance for pyoverdine bound to iron. If this receptor route is considered as a âdoorâ, and putting in mind that P. aeruginosa maybe ( or could be) as smart as a human being. As a human being, for instance, living in a house, supposedly with a door , this door may serve as an entrance for family and friends with good intentions, and through this same door, a thief or a burglar tries to or successfully makes an entrance, what would you do as an individual? Change the Lock and key just to prevent unwanted entrance. The fpvA of P. aeruginosa has been clearly demonstrated to be involved in its siderophore ( pyoverdine) biosynthesis (Shen et al. 2002) , and siderophore biosynthesis represents an attractive antibiotic target (Quadri, 2000), the fpvA type II may be considered to be a door through which ferripyoverdine complexes, bacteriocins, antibiotics, and other lethal agents passes, is the fpvA type II trying to change its lock and key? If this is true, it would justify a correlation between amino acid sequence diversity of immunogenic bacterial proteins and evasion of host immune defense mechanisms (Tummler and Cornelis, 2005).FpvA has been proposed to drive diversity at the pyoverdine locus (Smith et al.2005) and it has also been hypothesized that ferripyoverdine receptors are targeted by antibiotics and bacteriophages and serve as entry points (Wayne and Neilands, 1975; Guerinot, 1994; Andrews et al., 2003; Smith et al., 2005). P. aeruginosa alone will go to great lengths to evade the adverse effects of antibiotics and bacteriophages (Budzikiewicz, 2001). One way that this may be accomplished, as presented in this work (Osayande, J.O., 2010: see experimental procedures), may involve the ferripyoverdine receptors (as shown by the separate clustering of some of the test strains on the homology tree), the Pseudomonas aeruginosa strains So122, Pr332 and Lo059 were already speculated to belong to another group of the fpvAII receptor gene (Bodilis et al. 2009), and from my PCR analysis, a completely different primer set , different from the already existing primer sets used for ferripyoverdine receptor gene amplification (De Chial et al.2003, Ghysels et al.2004) were designed, and the FpvA sequences following amplification were aligned using the DNA Manager Software to construct homology trees and as already stated above, the strains are kind of deviating to form their own separate cluster, separate from their References strains (Strain Mi162 in particular), till now, there exists fpvAIIa and fpvAIIb, could these strains be said to belong to fpvA II c? It will be difficult to conclude based on the fact that the ferri-pyoverdine receptor genes in Pseudomonas aeruginosa is about 2500 bp in size, the fpvA variants identified from this study were not this large, a possible knowledge of the pyoverdine region, including the complete fpvA gene sequences (Poole et al., 1993; McMorran et al., 1996; Lamont and Martin, 2003) in the difficult-to-type P. aeruginosa strains (Please see previous paper: Osayande , J.O. 2010) , would be important to evolutionary studies to determine what portion of this region is favored by evolution. Such knowledge could provide rational starting points for the design of novel antimicrobial agents, especially in connection with their iron requirement (Miller et al., 1993; Clarke et al., 2001). Our future studies or other collaborative studies will plan to address this issue.
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