Iron and Pseudomonas aeruginosa biofilm formation

Abstract

Iron serves as a signal in Pseudomonas aeruginosa biofilm development. We examined the influence of mutations in known and putative iron acquisition-signaling genes on biofilm morphology. In iron-sufficient medium, mutants that cannot obtain iron through the high-affinity pyoverdine iron acquisition system form thin biofilms similar to those formed by the parent under low iron conditions. If an iron source for a different iron acquisition system is provided to a pyoverdine mutant, normal biofilm development occurs. This enabled us to identify iron uptake gene clusters that likely serve in transport of ferric citrate and ferrioxamine. We suggest that the functional iron signal for P. aeruginosa biofilm development is active transport of chelated iron or the level of internal iron. If the signal is internal iron levels, then a factor likely to be involved in iron signaling is the cytoplasmic ferric uptake regulator protein, Fur, which controls expression of iron-responsive genes. In support of a Fur involvement, we found that with low iron a Fur mutant was able to organize into more mature biofilms than was the parent. The two known Fur-controlled small regulatory RNAs (PrrF1 and F2) do not appear to mediate iron control of biofilm development. This information establishes a mechanistic basis for iron control of P. aeruginosa biofilm formation.pyoverdine

The Limitations of In Vitro Experimentation in Understanding Biofilms and Chronic Infection

“…Given the issues highlighted previously, how can we better represent in vivo conditions in our in vitro models? It is widely known, for P. aeruginosa at least, that different nutritional cues result in altered biofilm formation, virulence, motility, and QS [46,[113][114][115][116][117]. These differences become increasingly important when factors of clinical relevance, such as virulence and antimicrobial tolerance, are altered [13,118,119].…”

A Homologue of the 3-Oxoacyl-(Acyl Carrier Protein) Synthase III Gene Located in the Glycosylation Island of Pseudomonas syringae pv. tabaci Regulates Virulence Factors via N -Acyl Homoserine Lactone and Fatty Acid Synthesis

“…Iron acquisition and biosurfactant production were reported to influence biofilm formation (2,3). Normal biofilm is composed of bacterial cells and EPS, with large amounts of water in its structure (10).…”

“…However, when a WT strain of P. aeruginosa was incubated with lactoferrin, an iron chelator, a thick, mushroom-like structured biofilm was not observed by confocal scanning laser microscopy (2). The siderophore-defective mutant also formed only a thin uniform layer (2). Furthermore, overproduction of biosurfactants inhibited biofilm development in P. aeruginosa (8), probably because bacterial detachment from the biofilm occurred earlier and more extensively (3).…”

Phage selection for bacterial cheats leads to population decline

“…the production of exotoxins and endoproteases [51], and biofilms [52]). Further research is needed to elucidate the complex interrelationships between putative social and other life-history traits.…”