coli cells typically contain six times more RNA than DNA [39]. The nucleic acid mass fraction of the studied biofilms, however, was ca. 5 times lower than the nucleic acid dry weight content of E. coli. The calcium content (3% wt) of P. fluorescens EvS4-B1 biofilm equaled the total dry weight of all inorganic ions typically found in E. coli [39] and was

three times higher than the calcium content of the spent media. Korstens et al. studied the mechanical properties of P. aeruginosa biofilms as a function of calcium ion concentration and found that the apparent Young’s modulus, representing a measure of biofilm stiffness, increased strongly at a critical calcium concentration and subsequently remained selleck inhibitor constant at higher calcium levels [43]. This behavior was explained in terms of calcium ions crosslinking EPS components. Based on these results it is conceivable that the observed calcium accumulation in the biofilms studied here plays a significant role in crosslinking/bridging EPS components and herewith determining the geometry and maintaining the integrity of the observed structures. Unlike calcium, magnesium was not found to accumulate significantly Osimertinib in the biofilms relative to the spent media. Note that the chemical composition

of the biofilm presented in Table 1 is a semi-quantitative approximation rather than a rigorous, absolute quantitation, which is virtually impossible as the chemical heterogeneity of bacterial biofilms [44] precludes representative standards to be used in a number of the above assays. Cell and colony morphology filipin have been used by microbiologists in the identification of bacteria since van Leeuwenhoek developed

the optical microscope nearly three hundred and fifty years ago. The morphology of bacterial biofilms also may contain elements that can assist identification, but the features can only be observed under the electron microscope. The difficulty in preparing biofilm samples for examination by this technique without introducing artifacts has limited its usefulness. The emergence of cryomethods such as those described here has enabled the reliable application of electron microscopy to biofilm research. Recent results suggest that bacterial biofilms contain architectural motifs that may be useful in identifying these structures in medical, dental, and environmental samples. This approach has been used by Costerton and colleagues in studying intraamniotic infections [45] and affected bone in patients with osteonecrosis of the jaws secondary to bisphosphonate therapy [46]. Biofilms produced by P. fluorescens EvS4-B1, P. putida [27], and P. fulva (data to be presented elsewhere) isolates from the same environment share a common morphology suggesting that these microscopic features may be useful for in vivo identification.