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Pseudomonas aeruginosa is an environmental microorganism that is also an opportunistic pathogen, causing severe infections in immunocompromised individuals, including those with cystic fibrosis (CF). Increased airway iron concentrations and biofilm formation have been proposed to be potential factors in the persistence of P. aeruginosa in CF patients. Yu et al. (p. 6403–6413) show that a high level of iron enhances the production of the key biofilm matrix exopolysaccharide Psl to stimulate Psl-dependent biofilm formation and that exopolysaccharides can store iron within the biofilm matrix for the bacterial community. Their results not only imply a survival strategy for P. aeruginosa under high-iron environmental conditions but also may guide the use of iron chelators to interfere with P. aeruginosa biofilm formation in CF patients.
Iminosugars have great therapeutic potential as drugs for the treatment of many diseases. However, there is not a lot of information about the genes involved in their biosynthesis. Miyauchi et al. (p. 6414–6422) identified genes for the biosynthesis of an iminosugar, nectrisine, in the fungus Thelonectria discophora SANK 18292 and verified their requirement by disruption and complementation of those genes. The authors also demonstrated heterologous production of nectrisine by recombinant Escherichia coli. This work will contribute to the development of a microbial production system for nectrisine or its intermediates.
Heterogeneity in isogenic populations of microbial cells is a phenomenon that has gained more and more attention in fundamental studies of contemporary microbiology. In particular, the behavior of bacterial spore formers is of significant applied interest due to their stress resistance and role in health and disease. Pandey et al. (p. 6463–6471) open up the possibility of studying in Bacillus subtilis, the model organism for bacterial spore formers, the homeostasis of intracellular pH (pHi) both under control conditions and upon exposure to weak organic acid food preservatives at single-cell resolution. Their laboratory and others have shown that pHi is a key indicator of cellular growth capacity.
Hospital water distribution systems may be reservoirs for fungi responsible for nosocomial infections. Fusarium oxysporum was previously detected in the water distribution systems of five French hospitals. In studies by Edel-Hermann et al. (p. 6483–6489), isolates representative of all hospital units were characterized using molecular tools and vegetative compatibility grouping. A clonal lineage of F. oxysporum inhabiting the water distribution systems of all hospitals was identified. The existence of this clonal lineage, which appears to be particularly adapted to water networks, represents a potential risk for human infection and raises questions about its worldwide distribution.
Microbial cross-contamination from surfaces to food can contribute to foodborne disease. This idea is reflected in the pop culture notion of the “five second rule.” Miranda and Schaffner (p. 6490–6496) explored this topic using four different surfaces, four different foods, four different contact times, and two bacterial preparation methods. Contact time, food, and surface type all had highly statistically significant effects on bacterial transfer. Although longer contact times result in more transfer, other factors, including food and surface type, are of equal or greater importance. Some transfer takes place “instantaneously” (in less than 1 second), disproving the “five second rule.”